Anatomy and Properties of BambooW. Liese

Institute of Wood Biology and Wood Preservation of the FederalResearch Centre for Forestry and Forest Products,

Leuschnerstr, 91, 2050 Hamburg, Federal Republic of Germany

Abstract

The numerous alternatives in the use ofbamboo depend on the unique properties ofits culm. In order to understand the anatom-ical and chemical make-up and its ensuingmechanical properties, an attempt has beenmade to summarize the accessible informa-tion.

Anatomy

Gross anatomy: The properties of theculm are determined by its anatomical struc-ture. The culm consists of internodes andnodes. At the internodes, the cells are axiallyoriented, whereas at the nodes, cells providethe transverse interconnections. No radial cellelements, such as rays, exist in the inter-nodes. Within the nodes an intensive branch-ing of the vessels occurs. These also bendradially inward and provide transverse con-duction through the nodal diaphragms, sothat all parts of the culm are interwoven. Theouter part of the culm is formed by two epi-dermal cell layers, the inner appearing thickerand highly lignified. The surface of outermostcells are covered by a cutinized layer with awax coating. The inner parts of the culm con-sist of numerous sclerenchyma cells. Anylateral movement of liquids is therefore muchhindered. Pathways for penetration are thusonly the cross ends of the culm and to a muchsmaller extent the sheath scars around thenodes.

The gross anatomical structure of a trans-verse section of any culm internode is deter-mined by the shape, size, arrangement andnumber of the vascular bundles. They areclearly contrasted b y the darker coloredsclerenchymatous tissue against the paren-

chymatous ground tissue. At the peripheralzone of the culm the vascular bundles aresmaller and more numerous, in the innerparts larger and fewer (Figs. 1, 2). Within theculm wall the total number of vascularbundles decreases from bottom towards thetop, while their density increases at the sametime. The culm tissue is mostly parenchymaand the vascular bundles which are com-posed of vessels, sieve tubes with companioncells and fibres. The total culm comprisesabout 50% parenchyma, 40% fibre, and10% conducting tissues (vessels and sievetubes) with some variation according tospecies. The percentage distribution andorientation of cells show a definite patternwithin the culm, both horizontally and ver-tically. Parenchyma and conducting cells aremore frequent in the inner third of the wall,whereas in the outer third the percentage offibers is distinctly higher. In the vertical direc-tion the amount of fibres increases frombottom to top and that of parenchymadecreases (Fig. 3) The common practice ofleaving the upper part of a cut culm unused inthe forest is therefore a waste with regard toits higher fibre content.

Parenchyma: The ground tissue consistsof parenchyma cells, which are mostly ver-tically elongated (100 x 20 urn) with short,cube-like ones interspersed in between. Theformer are characterized by thicker walls witha polylamellate structure (Fig. 4); theybecome Iignified in the early stages of shootgrowth. The shorter cells have a denser cyto-plasm, thinner walls and retain their cyto-plasmic activity for a long time. The functionof these two different types of parenchymacells is still unknown.

Of interest in the structure of parenchymawalls is the occurrence of warts in many taxa

See also recent GTZ publication: Bamboos - Biology, Silvics, Properties, Utilization by Liese, 1985 - Ed,

196

Figure 2. Overview o f 6 culm sec t i on , Dendrocalamus giganteus.

Ftgure 2. Three-dlmenslonal view of culm tissue withvascular bundles.

like Bombusa, Cephalostachyum, Dendro-calamus, Oxytenanthera, Thyrostachys,which have not been observed so far in theparenchyma of hardwoods. Genuine wartshave to be carefully distinguished from cyto-plasmic debris, which are also frequent inparenchyma cells after the death of the proto-plast. Their distribution is variable from verydense to sparse. Among the speciesexamined the parenchyma cells appear topossess a even higher number and density ofwarts than fibres and vessel members.Their size varies from 120 - 520 nm. Theoccurrence of warts in the lignified paren-

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2.10.18.26. 2 10.1826. 2.10.18.26internodes

parenchyma fi bres

vessels, phloem

Figure 3. Percentage of cell type in the vertical d i rec t i onof a culm;Cephalostachyum perqracile.

chyma cells of bamboo is perhaps an expres-sion of the close association of lignin-likenature of warts, since warts have not beenobserved in non-lignified cells (Parameswaranand Liese, 1977).

Vascular bundles: The vascular bundlein the bamboo culm consists of the xylem withone or two smaller protoxylem elements andtwo large metaxylem vessels (40 - 120 urn)

and the phloem with thinwalled, unlignifiedsieve tubes connected to companion cells(Fig. 5). The vessels possess large diametersin the inner parts of the culm wall and becomesmall towards outside. These water conduct-ing elements have to function throughout thelifetime of a culm without the formation ofany new tissue, as in the case of hardwoodsand softwoods with cambial activity. In olderculms, vessels and sieve tubes can becomepartly impermeable due to depositions of gum-like substances, thus losing their conduc-tivity which may cause death of the agedculms. The one or two tracheary elements ofthe protoxylem have mostly annular thicken-ings. They are local areas of stasis accumulat-

ing wall material, which are connected witheach other by membranes in the early stagesof development. During extension growth ofthe cell, they are disrupted.

The walls of metaxyiem vessels of bam-boo are characterized by a middle lamella anda primary wall together with a well developedzonation of the secondary wall into Sl andS2. Whereas the Sl possesses a flat spiralarrangement of fibrils (90 - 95O) the S2 zoneshows a slight deviation from the known fibrilorientation in tracheids. The fibrils arearranged at an angle of 30 - 90 to the cellaxis; also microlamellae are present withfibrils arranged in a fan-like fashion. This wallstructure perhaps to be considered asnormal, i s modified In some taxa like Oxy-tenatherd abysinica a n d Melocanna bam-busoides to such an extent that a polylamellaeconstruction results, resembling a paren-chyma wall with the herringbone pattern offibrillar arrangement whereby the number oflayers are mostly restricted to two to four(Parameswaran a n d Liese. 1 9 8 0 ) . W a r t shave been observed in the metaxylem ofvessels of Oxytenanthera nigrociliata, Melo-canna bambusoides. Gigantochloa a l t e r . f.nigra. Schizostachyum blumei. a n d Sbrachycla dium. The pi ts of these vesselstowards the surrounding parenchyma ofadjacent vessel elements are slightly bor-dered. Their membrane consists of fibrils witha net-like texture, resembling hardwood pits,

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Figure 6. Different types of vascular bundles. I: Phyllostachys edulis. I/ Cephalostachyum pergracile.III Oxytonanthcra albociliata, IV: Thyrsostachys oliveri,

199

Of particular interest is also the presenceof a protective layer in the parenchyma cellsadjacent to metaxylem vessels; it consists ofpolysaccharides of the cellulose and hemicel-lulose type without lignification. This observa-tion extends the presence of such a layer tomonocots, besides dicots and softwoods.

Both the metaxylem vessels and thephloem tissue are surrounded by scleren-chyma sheaths. They differ considerably insize, shape and location according to theirposition in the culm and the bamboo species(Grosser and Liese, 1971; 1973; Wu andWang, 1976; Jiang and Li, 1982).

Four to five major types of vascularbundles can be differentiated (cf. Fig. 6).

Type I : consisting ,of one central vascularstrand; supporting tissue only assclerenchyma sheaths;

Type II :

Type III :

Type IV :

Type V :

consisting of one central vascularstrand; supporting tissue only assclerenchyma sheaths; sheath atthe intercellular space (pro-toxylem) strikingly larger than theother three;

consisting-of two parts, the centralvascular strand with sclerenchymasheaths and one isolated fibrebundles;

consisting of three parts, the cen-tral vascular strand with smallsclerenchyma sheaths and twoisolated fibre bundles outside andinside the central strand;

a semi-open type representing afurther link in the evolution ten-dency _

The vascular bundle types and their dis-tribution within the culm correlate with thetaxonomic classification system of Holttum(1956) based on the ovary structure.

For example:

Type I alone :

Type II alone :

Type II and III :

Type III alone :

Arundinaria,Phyllostachys, Fargeria,Sinanundinaria

Cephalostachyum,Pleioblastus

Melocanna,Schizostachyum

Oxytenanthera

Type III and IV : Bambusa,Dendrocalamus.Gigantochloa. Sinoclamus

Leptomorph genera have only the vascu-lar bundle type I, whereas pachymorphgenera possess types II, III and IV. Size andshape of the vascular bundles vary across aninternode but also with the height of a culm.

Fibres: The fibres constitute the scleren-chymatous tissue and occur in the internodesas caps of vascular bundles and in somespecies additionally as isolated strands. Theycontribute to 40 - 50% of the total culmtissue and 60 - 70% by weight. The fibresare long and tapered at their ends. The ratioof length to width varies between 150 : 1 and250 : 1. The length shows considerable varia-tion both between and within species.

Fibre measurements for 78 species weresummarized by Liese and Grosser (1972).Generally, the fibers are much longer thanthose from hardwoods. Different values havebeen reported for one and the same species.The reason is mainly due to the considerablevariation of fibre length within one culm.Across the culm wall the fibre length oftenincreases from the periphery, reaches itsmaximum at about the middle and decreasestowards the inner pan. However, few speciesshow a general decrease from the outer parttowards the center. The fibres in the innerpart of the culm are always much shorter (20- 40%).

An even greater variation of more than100% exists longitudinally within one inter-node: the shortest fibres are always near tothe nodes, the longest in the middle part (Fig.7). With increasing height of the culm there

node

node

fibre lenghtFigure 7. Variation of fibre length within one, internode.

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occurs only a slight reduction in fibre length.As the fibre length serves as an importantcriterion for pulping suitability, any measure-ment has to consider the distinct pattern ofvariation within the culm by taking represen-tative samples.

The fibre length is positively and stronglycorrelated with fiber diameter, cell wall thick-ness and internode diameter, but not withlumen diameter and internode length. Thefibre diameter varies between 11 and 19 urn,the lumen diameter between 2 - 4 um andthe cell wall thickness between 4 -- 6 urn.The ultrastructure of most of the fibres is char-acterized by thick polylamellate secondarywalls. This lamellation consists of alternatingbroad and narrow layers with differing fibrillarorientation (Fig. 8). In the broad lamellae thefibrils are oriented at a small angle to the fibreaxis, whereas the narrow ones show mostly atransverse orientation 1 The narrow lamellaeexhibit a higher lignin content than thebroader ones. A typical tertiary wall is not pre-s e n t , b u t i n s o m e taxa (Oxytenanthera.Bambusa, Ochlandra) warts cover the inner-most layer (Parameswaran and Liese, 1976;1981) The polylamellate wall structure of thefibres especially at the periphery of the culmleads to an extremely high tensile strength, asdemonstrated in engineering constructionswith bamboo culms. Fig. 9 demonstrates

Figure 9. Model of the polylamellate structure of a thickwalled bamboo fibre

the finestructural make-up of a bamboo fibre.The polylamellate structure does not exist inthe cellwalls of fibres or tracheids of normalwood.

In culms with curved internodes noreaction tissue comparable with the tensionwood-fibres of hardwoods has beenobserved, Some of the fibres with secondarywalls possess septa in their lumina as in thecase of hardwoods. The obvious difference isthe presence of secondary thickening of theotherwise normally formed septum with amiddle lamella-like layer and a primary wal1.In the polylamellate fibres it is surprising tofind septa containing several secondary walllamellae, which are continued into the longi-tudinal wall of the fibres. These septa arelignified, a phenomenon normally absent inhardwood fibres.

Phloem: The phloem consists of largethin-walled sieve tubes, among which smallercompanion cells are distributed. The finestructural studies have revealed the presenceof plastids in sieve tubes characterized byosmiophilic cuneate proteinaceous bodiesand lattice-like crystalloids with paralleltubular units. The plastids in sieve elementsare devoid of starch. This type of plastid (PIIb) is characteristic of the Poaceae. ThusBambusaceae belonging to the Poaceae ofthe Order Poales constitute yet another groupwith a definite plastid type, implying itstaxonomic significance, as has been sug-.gested for other families.

The density of the cytoplasm is caused bythe presence of numerous ribosomes. At theperiphery there occurs a rough endoplasmicreticulum, which is extensively developed.Mitochondria with well defined cristae arealso present. Distinct, P-protein-like filamenthave not been observed at any stage. Dictyo-somes are few. Occasionally, microbodies-like structures have been noticed with fila-mentous contents. The peripherally locatednucleus is elongated and lobed. With theaging of the sieve elements there originates avacuole in the centre of the cell, restricting thecytoplasm to the periphery. The plastids stillcontain well-developed cuneate protein-aceous bodies in addition to paracrystallinestructures as well as vesicular and tubularunits. The sieve elements are connected witheach other by sieve pores which are lined withsmall callose platelets.

The wall of the sieve element is charac-terized by microfibrils oriented parallel to eachother in a concentric manner around the celland perpendicular to cell axis, creating astrong birefringence in the polarizing micro-scope. The sieve element wall contains gen-erally only cellin material without obvioussigns of lignification even in mature stages.Due to the prolonged and continuous growthof bamboo culms over more than 30 years it isconceivable that the sieve elements andmetaxylem, vessels remain active in theirtransport function over several decades. Dis-tributed among the sieve elements are com-panion cells, which are characterized bydense cytoplasm and a large nucleus. Mito-chondria are numerous and the endoplasmicreticulum is extensively ramified. Plastids arefew, The companion cells are connected withthe sieve elements by plasmodesmata, whichare branched on the companion cell side witha weak callose development.

Chemical Properties

Chemical constitution: The main con-stituents of the bamboo culms are cellulose,hemicellulose and lignin; minor constituentsconsist of resins, tannins, waxes and inor-ganic salts. The composition varies accordingto species, the conditions of growth, the ageof the bamboo and the part of the culm.Because the bamboo culm tissue matureswithin a year when the soft and fragile sproutbecomes hard and strong, the proportion oflignin and carbohydrates is changed duringthis period. However, after the full maturationof the culm, the chemical composition tendsto remain rather constant. Tables 1, 2 giveapproximate chemical analysis for some bam-boo species. Small differences exist along aculm, as shown in Table 2. The nodes containless water-soluble extractives, pentosans, ash,and lignin but more cellulose than the inter-nodes. The season influences the amount ofwater-soluble materials, which are higher inthe dry season than in the rainy season. Thestarch content reaches its maximum in thedriest months before the rainy season andsprouting. The ash content (1 - 5%) ishigher in the inner part than in the outer one.The silica content varies on an average from0.5 to 4%. increasing from bottom to top.Most silica is deposited in the epidermis, the

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Table 1. Chemical compoadtion of some bamboo0 (Tamolang et al. 1980)

Species

Gigantochlca levis

Gigantochloa aspera

Bambusa vulgaris

Range of valuesfor 10 Indianbamboo species

Range of valuesfor 10 Japanese,Burmese and Indonesianbamboo species

H&cellulose Pentosans Lignin Akoholbenzene(%) (%) (%) (%)

62.9 18.8 24.2 3.2

61.3 19.6 25.5 5.4

66.5 21.1 26.9 4.1

- 15. 1 22.0- 0.2-21.5 32.2 3.2 6.9

61.9- 17.5- 19.8- 0.9-70.4 22.7 26.6 10.8

H o t 1 %water NaOH(%) (%)4.4 28.3

3.8 22.3

5.1 27.9

3.4- 15 .0 -21.8 3.2

5.3- 22.2.11.8 29.8

A s h(%)

5.3

4 .1

2.4

1.7-2.1

0 8-3.8

Silica( % )

2.8

2.4

1.5

0.44

0 l-1.7

Table 2. Chemical coniposition of Phyllostachys pubescens at different heights (Li 1983)

Hot water 1%Holocellulose Pentosans Lignin Ash alcoholbenzene extracts NaOH

(%) (%) (%) (%) (%) (%) ( % )

upper culm 54.1 31.8 24.7 1.2 6.0 7.0 25.6

middle culm 53.6 30.8 24.5 1.2 7.6 8.5 27.6

lower culm 54.4 32.9 24.0 1.1 7.4 9.3 28.3

skin zone, whereas the nodes contain littlesilica and the tissues of the internodes almostnone. Silica content affects the pulping pro-perties of bamboo.

Cellulose and hemicellulose: Thecellulose in bamboo amounts - as holocellu-lose - to more than 50% of the chemicalconstituents. As in other plants it consists oflinear chains of 1, 4 bonded hydroglucoseunits (C2H1206). The number of glucose unitsin one molecular chain is referred to as thedegree of polymerization (DP). The DP forbamboo is considerably higher than for dico-tyledoneous woods. Cellulose is difficult toisolate in pure form because it is closely asso-ciated with the hemicelluloses and the lignin.

by hardwoods. With regard to the presence ofarabinose it is closer to softwoods. Thus, thebamboo xylan is intermediate between hard-wood and softwood xylans. These resultsindicate that the bamboo xylan has theunique structure of Gramineae (Higuchi,1980).

Lignin: After cellulose, lignin representsthe second most abundant constituent in thebamboo and much interest has been focusedon its chemical nature and structure. Bamboolignin is a typical grass lignin, which is built upfrom the three phenyl-propane units p-coumaryl, coniferyl, and sinapyl alcoholsinterconnected through biosyntheticpathways.

More than 90% of the bamboo hemicellu- Bamboo grows very rapidly and com-loses consist of a xylan which seems to be a 1, pletes the height growth within a few months4-linked linear polymer forming a 4-0-methyl- reaching the full size. The growing bambooD-glucuronic acid, L-arabinose, and D-xylose shows various lignification stages from thein a molar ratio of 1 .O : 1.3 : 25 respectively. bottom to the top portions of the same culmIt is in the main chain linear, but appears to be (Itoh and Shimaji, 1981). The lignificationdifferent from the xylan found in the woods of within every internode proceeds downwardgymnosperms with regard to the degree of from top to bottom, whereas transversely itbranching and molecular properties. Further- proceeds from inside to outside. During themore, the bamboo xyIan contains 6 - 7% of height growth lignification of epidermaf cellsnative acetyl groups, which is a feature shared and fibres precede that of ground tissue

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parenchyma. Full lignification of bambooculm is completed within one growingseason, showing no further ageing effects. Nodifference has been detected in lignin com-position between vascular bundles and paren-chyma tissue (Higuchi et al., 1966). Bamboohas been chosen as one of the suitable plantsto study the biosynthesis of lignin. lnitially,these investigations were almost exclusivelybased on feeding experiments with radio-active precursors and it has been known thatlignin is synthesized from glucose formedby photosynthesis via the Shikimic acidpathway (Higuchi, 1969). Several keyenzymes involved in the synthesis of shikimicacid were isolated from bamboo shoots(Fengel and Shao, 1984; 1985).

Physical and MechanicalProperties

Moisture content: The moisture con-tent varies within one culm and is influencedby its age, the season of felling and thespecies, In the green stage greater differencesexist within one culm as well as in relation toage, season and species. Young, one-yearold shoots have a high relative moisture con-tent of about 120 - 130% both at bottomand top. The nodes, however, show lowervalues than the internodes. These differencescan amount to 25% of the water content andare larger at the base than at the top. In culmsof 3 - 4 years the base has a higher moisturecontent than the top, e.g. for Dendrocalamusstrictus about 100% and 60% relativemoisture content respectively. The moisturecontent across the culm wall is higher in theinner part than in the outer part.

The season has a great influence on thewater content of the culm, with a minimum atthe end of the dry period, followed by amaximum in the rainy season, During thisperiod the stem can double its water content.The variation due to the season is higher thanthe differences between base and top as wellas between species. Among species the watercontent varies even in the same locality. Thisis mainly due to the variation in the amount ofparenchyma cells, which corresponds towater holding capacity (Liese and Grover,1961). The considerable differences in themoisture content of freshly felled culms haveto be considered when determining the yieldof bamboo expressed by its fresh weight.

Fibre saturation point and shrink-age: The fibre saturation point is influencedby the composition of the tissue and theamount of hygroscopic extractives. Sincefibres and parenchyma have apparently a dif-ferent fibre saturation point, their varyingamount within a culm leads to differentvalues. The fibre saturation point conse-quently differs within one culm and betweenspecies. For Dendrocalamus strictus the meanvalue was determined to be about 20%, forPhyllostachys pubescens about 13% (Ota,1955) .

Unlike wood, bamboo begins to shrinkright from the beginning of seasoning. Theshrinkage affects both the thickness of theculm walls and the circumference. Seasoningof mature bamboo from green condition toabout 20% moisture content leads to ashrinkage of 4 to 14% in the wall thicknessand 3 to 12% in diameter. Bamboo tissueshrinks mainly in the radial direction, and theminimum deformation occurs in the axialdirection. The tangential shrinkage is higherin the outer parts of the wall than in the innerparts. The shrinkage of the whole wallappears to be governed by the shrinkage ofthe outermost portion, which possesses alsothe highest specific gravity. Mature culmsshrink less than immature ones.

Value of shrinkage from freshly felled tothe oven-dry state were determined for Phyl-lostachys pubescens as follows: tangential:8.2% for the outer part of the wall and 4.1%for the inner; radial: 6, 8% for the outer partand 7.2% for the inner; longitudinal: 0.17%for the outer part and 0.43% for the inner.Shrinkage starts simultaneously with thedecrease of moisture content but does not con-tinue regularly As water content diminishesfrom 70 to 40%, shrinkage stops; below thisrange it can again be initiated. Parenchymatissue shrinks less in bamboo than in timber,while vascular fibres shrink as much as intimbers of the same specific gravity. When themoisture content is low, swelling due toabsorption of water is almost equal to shrink-age. Moist heating leads to irreversible swellingin all directions. The percentage of swellingdecreases with an increase of basic density(Kishen et al., 1958; Sekhar and Rawat,1964).

Seasoning: The cut bamboo should firstb e dried for at least four weeks preferably

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standing upright. Lying horizontally almostdoubles the drying time.

Air seasoning under cover is preferred,but seldom possible. Kiln seasoning undercontrolled conditions can be performed inabout two to three weeks, but is considered tobe uneconomical. The different seasoningbehaviour of bamboo species is chiefly due t othe different culm wall thickness which is themost important factor in controlling the rate ofdrying. The bottom part, therefore, takesmuch longer to season than the top portion.The rate of drying of immature cuims is gen-erally faster than that of mature ones, b u tsince the former have a higher moisture con-tent they need longer. In the initial stagesdrying occurs quite rapidly, but slows downgradually as drying progresses.

Compared with timber of the samespecific gravity, the drying period needed forair or kiln drying is longer due to the higherinitial moisture content and the presence o fwater soluble extractives in the parenchymacells. Their hygroscopicity in humid air is ofabout the same degree as invert sugar. Thewater absorption of dried bamboo therefore isquite rapid compared with that of timber.Bamboos, from which water-soluble extrac-tives have been removed by soaking, d r yfaster and take up moisture slower thanuntreated ones.

Seasoning defects: Several defects canoccur during seasoning. They may be due tothe poor initial condition of the culm, due toexcessive shrinkage during drying or both.

End splitting is not so common or severeas in timber. Surface cracking can occurduring drying with all species. Cracks start atthe nodes but their extent depends on thespecies and wall thickness. Thick-walledmature bamboo is especially liable to crack. Adeformed surface of the round cross-sectionof immature bamboo is common. Thick-walled species evince an uneven outer sur-face, and cracks quite often develop on theinner side of the wall. Considerable shrinkagecan take place in the middle part of the inter-nodes, which become concave.

Collapse is a most serious seasoningdefect. It occurs during artificial as well asnatural drying processes and leads to cavitieson the outer surface and to wide cracks on theinner part of the culm. Green bamboo is aptto collapse due to differential tension during

drying. This shrinkage takes place in the earlystages of seasoning. The outer fiber bundlesare pressed together but the inner ones arestretched and this causes severe stresses.Immature bamboo is more liable to collapsethan mature. Because of faster drying duringthe dry season, collapse occurs more oftenthan during the rainy season. The lowerportion with thicker walls is more liable tocollapse than the upper portion. Slow dryingbamboo species are apparently more liable tocollapse than others.

To avoid seasoning defects, severalmethods of pretreatment have been tried.Soaking in water for two to six weeks did notimprove the seasoning behaviour. Actuallythe devaluation due to checking, splitting andcollapse was more severe in soaked piecesthan in controls. Also water-soaked bamboosmells unpleasant, due to change of i tsorganic constitutents. On the other hand,pieces which have been soaked are not liableto be attacked by powder post beetles duringsubsequent storage as the food material forthe beetles leaches out during soaking.

Presteaming of green bamboo culms didnot improve the seasoning as cracking andcollapse still occur. Heat treatment over anopen fire can be applied if the culms arehalf dry already, i.e. with not more than 50%moisture content.

Changes in colour can occur during sea-soning. Fresh bamboo normally looks greenor rather yellowish according to the stage ofmaturity, it changes during seasoning to alight green shade. Immature bamboos turnemerald green and mature ones pale yellow.Culms which are slowly air-dried develop adarker yellow colour than those which aredried rapidly in a kiln.

Specific gravity and mechanical pro-perties: The specific gravity varies fromabout 0.5 to 0.8 (0.9) g/cm3. The outer partof the culm has a far higher specific gravitythan the inner part. The specific gravity in-creases along the culm from the bottom to thetop. The mechanical properties are correlatedwith specific gravity. Bamboo possesses ex-cellent mechanical properties. These dependmainly on the fiber content and therefore varyconsiderably within the culm and betweenspecies. At the base, for example, the bend-ing strength of the outer part is 2 - 3 timesthat of the inner part. Such differences

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become smaller with increasing height of theculm. With the decreasing thickness of theculm wall there is an increase in specificgravity and mechanical strength of the innerparts which contain less parenchyma andmore fibers, whereas these properties in theouter parts change only slightly. The variationof strength properties is much greater in thehorizontal direction than in the vertical direc-tion (Janssen, 1981),

A close correlation exists between specificgravity and maximum crushing strength. Itseems that resistance to compression parallelto the grain is more or less uniform, hardlybeing affected by the height of the culm. Forbending strength and modulus of elasticity,higher values were obtained from the upperpart. Bamboo splints with the epidermisdownwards have a higher fiber stress, bend-ing strength and modulus of elasticity thanthose with the epidermis upwards. Splintswithout nodes have about one to two timesthe ultimate tensile strength of timbers such asspruce, pine, oak and beech.

The specific gravity of the nodes is gen-erally higher .than that of the internodes dueto less parenchyma, whereas bendingstrength, compression strength and shearstrength are lower. This is due to the irregu-larity of the grain, caused by the arrangementof cells. The presence of nodes thus leads to a

remarkable reduction in all strength proper-ties.

Since there are still no standard methodsof evaluating the strength properties of bam-boo, as in the case of wood, the results arebased on different methods of testing and onwidely varying dimensions (Limaye, 1952;Sekhar and Bhartai, 1960).

The superior tensile strength of bamboo inrelation to wood and steel is demonstrated bythe following comparison: a steel bow of acertain quality (SA 37) of 1 cm2 with 1 mlength has a weight of 0.785 kg and aultimate tensile force of ca. 40 kH; a stickfrom wood with the same length and weightwould have a cross section of 13.5 cm2 and abreaking point at 80 kN, but one from bam-boo with 12 cm2 would resist up to 240 kN;e.g. six times that of steel. The moisture con-tent has a similar infIuence on the strength asit has in timber. Generally in the dry conditionthe strength is higher than in the green condi-tion. This increase in strength with seasoningis more obvious for younger culms than forolder ones. The differences between the airdry and green condition are sometimesrelatively small, especially for bending andcleavage (cf. Table 3) (Ota, 1953).

Table 3. Mechanical properties of Phyllostachys pubescens in the water saturated, air dry andoven dry state (Suzuki 1950)

Property

Bending s t reng thN/mm2

Cleavage s t rengthN/mm2

Shear s t rengthN/mm2

Part

0uter

inner

outer

inner

w h o l e

w h o l e

6

5

watersa tura ted

250

120

7

6

6

9

air dry

270

144

8

8

7

11

oven dry

370

160

8

18

Janka-HardnessN/mm2

outer

inner

e n d 49 63 91

s ide 22 25 37

e n d 27 32 66

s ide 13 17 37

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Influence Of Age

Age is an important factor for the devel-opment of strength properties. It is a generalassumption that bamboos mature until aboutthree years and have then reached their max-imum strength. Investigations with Dendro-calamus strictus have shown that in the greencondition older bamboo culms have higherstrength properties than younger ones (themoisture content of the latter is much higher) In the dry condition, however, higher valueswere obtained at the age of one and two yearsthan from older culms. Tests on splints fromthe central portion of the culm wall indicatedbetter strength properties for one year oldbamboo than for two years old ones, whereasthose of culms of later years were slightlylower. Comprehensive tests by Zhou (1981)revealed a further increase of strength proper-ties with age, viz for radial and tangentialbending strength up to 8 years and for tensilestrength and compression strength (parallel tothe grain) up to 5 years. Older culms (10years) showed a decrease in all strength pro-perties.

Besides the above mentioned variationsof properties within one culm, marked differ-ences exist among individual culms from thesame stand and even more among those fromdifferent localities. Needless to say. strengthproperties vary considerably between differentspecies.

References

FengeI. D. and Shao, X. 1984. A chemicaland ultrastructural study of the bamboospecies Phyl lostachys makinoi Hay.Wood Science and Technology 18: 103-112.

Fengel. D. and Shao, X. 1985. Studies onthe Iignin of the bamboo species Phyl-Iostachys makinoi Hay. Wood Scienceand Technology 19: 131-137.

Grosser. D. and Liese. W. 1971. On theanatomy of Asian bamboo with specialreference to their vascular bundles.Wood Science and TechnoIogy5: 290-312 .

Grosser, D. and Liese. W. 1973. Presentstatus and problems of bamboo classifica-tion. J. Arnold Arboret. 54: 293-308.

Higuchi, T., Kimura, N. and Kawamura, I.1966. Difference in chemical propertiesof lignin of vascular bundles and ofparenchyma cells of bamboo. MokuzaiGakhaishi 12: 173-178.

Higuchi, T. 1969. Bamboo Iignin and its bio-synthesis. Wood Research 48: l-14,(Kyoto)

Higuchi, T. 1980. Chemistry and biochem-istry; bamboo for pulp and paper of bam-boo. Bamboo Research in Asia. Ed. G.Lessard, A. Chouinard. IDRC, 51-56,Ottawa.

Itoh, T. and Shimaji, K. 1981. Lignification ofbamboo culm (Phyllostachys pubescens)during its growth and maturation. Bam-boo Production and Utilization. 104-l 10.In: Proc. XVII IUFRO Congress Group5.3. Ed. T. Higuchi. Kyoto, Japan.

Janssen, J.J.A. 1981. The relationshipbetween the mechanical properties andthe biological and chemical compositionof bamboo. Bamboo Production andUtilization, 27-32. In: Proc. XVII IUFROCongress Group 5.3. Ed. T. HIguchi,Kyoto, Japan.

Jiang Xin and Li Qian. 1982. Preliminarystudy on vascular bundles of bamboonative to Sichuan, Journal of BambooResearch 1: 17-21.

Kishen, J., Ghosh, P.P. and Rehman M.A.1958. Studies in moisture content,shrinkage, swelling and intersection pointof mature Dendrocalamus strictus (malebamboo). Indian Forest Records, NewSer. 1: 11-30.

Li, 1983. Report. Institute of Wood Industry,Chinese Academy of Forestry, Beijing.

Liese, W. and Grover, P.N. 1961. Unter-suchungen uber den Wassergehalt vonindischen Bambushalmen. Ber. DeutscheBotanische Gesellschaft 74: 105- 117.

Liese. W. and Grosser, D. 1972. Unter-suchungen zur Variabilitat der Faserlangebei Bambu s . Holzforschung 26: 202-211.

Liese. W. 1985. Bamboos biology, silvicsproperties, utilization. Gesellschaft furtechnische Zusammenarbeit Schriften-reihe, Eschborn (in press) _

Limaye, B.E. 1952. Strength of bamboo(Dendrocalamus strictus). Indian ForestRecords N.S. 1: 17.

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Ota, M. 1953. Studies on the Properties ofbamboo stem (Part 9). On the reIationbetween compressive strength parallel tograin and moisture content of bamboosplint. Bulletin of the Kyushu UniversityForests 22: 87- 108.

Ota, M. 1955. Studies on the properties ofbamboo stem (Part 11). On the fiber-saturation point obtained from the effectof the moisture content on the swellingand shrinkage of bamboo splint. Bulletinof the Kyushu University Forests 24: 61-72.

Parameswaran, N. and Liese, W. 1976. Onthe fine structure of bamboo fibres. WoodScience and Technology 10: 231-246.

Parameswaran, N. and Liese, W. 1977.Occurrence of warts in bamboo species.Wood Science and Technology 11: 313-318.

Parameswaran, N. and Liese, W. 1980.UltrastructuraI aspects of bamboo cells.Cell. Chem. Technology 14: 587609.

Parameswaran, N. and Liese, W. 1981. Thefine structure of bamboo. Bamboo Pro-duction and Utilization. 178-183. In:Proc. XVII IUFRO Congress Group 5.3.Ed. T. Higuchi. Kyoto, Japan.

Sekhar, A.C. and Bhartari, R.K. 1960,Studies on strength of bamboos: a noteon its mechanical behaviour. IndianForest, 86: 296-301, Dehra Dun.

Sekhar, A.C. and Rawat, M.S. 1964.-Somestudies on the shrinkage of Bambusunutans. Indian Forest 91: 182-188,Dehra Dun.

Suzuki, Y. 1950. Studies on the bamboo(VI). Dependence of the mechanical pro-perties of PhyIIostachys pubescens Magelet H. de Lehaie upon the moisturecontent. Bulletin Tokyo UniversityForests 38: 181-186.

Tamolang, F.N., Lopez, F.R., Semana,J.A., Casin, R.F., and Espiloy, Z.B.1980. Properties and utilization of Philip-pine bamboos. Bamboo Research inAsia, ed. G. Lessard, A. Chouinard.IDRC, 189-200, Ottawa.

Wu, S. and Wang, H. 1976. Studies on thestructure of bamboos grown in Taiwan.Bulletin of the National Taiwan University16: 79.

Zhou, F.C. 1981. Studies on physical andmechanical properties of bamboo woods.Journal of the Nanjing TechnologicalCollege of Forest Products 2: 1-32.

Anatomical Studies on Certain BamboosGrowing in Singapore

A.N. Rao

Depar tment o f Botany, Nat ional Un ivers i ty o f S ingapore,Lower Kent R idge Road, S ingapore 0511

Abstract

Bamboos are common useful plants in theAsian tropics mostly used by the rural peoplefor food, housing and other utility purposes.Like other natural resources their productionis decreasing and there is a renewed interestto promote thei r cul t ivat ion for economicbenefits. The constraints are several includingthe bas ic in fo rmat ion on p lant g rowth , itsstructure and function. It is amazing to see somuch paucity in our knowledge on bambooanatomy. In this paper the anatomical detailsof the shoot apex, axillary buds, young andmature stems, culm and regular leaves androots are presented. The need for fu r therbas ic s tud ies towards improv ing the p lan tgrowth and production is stressed.

Apart from individual scientific contribu-tions, active teamwork is necessary to pro-mote both research and manpower training inAsian countries. The latter is most importantand urgent since there are very few in the fieldwho are familiar with the taxonomy, growthand reproduction of bamboos. Multinationalwork programmes based on the model o fcertain on-going projects are suggested.

Introduction

The history of bamboos is inextricablyinterwoven with the history of man, especiallyin tropical countries. Most of the developingand poor countries are in the tropical zoneand bamboo is a poor mans plant. The familyGramineae is one of the biggest among angio-sperms with 450 genera and 4,500 species(Willis, 1951). Bamboos are classified into 21genera and 170 species. In tropical Asia alonethere are 14 genera and 120 species (Drans-

field, 1980) Bamboos are the woody grassesthat are comparatively less specialised thanthe herbaceous species in Gramineae. Thetaxonomy of Bambusoideae is based onspikelet structure (Gilliland, 1971) andamong others, the limitations imposed by a)infrequent flowering of the various species,and b) lack of suitable fresh floweringmaterials for study are obvious. Hence,attempts are also made to use vegetativecharacters and here again the details areenumerated by very few observations onfresh materials and the emphasis is based onthe morphology of culm leaves (Gilliland,1971; Holttum, 1958). Although bamboosposses fairly conservative structures manyvariations are seen at subspecific or varietallevels. A detailed study especially in the field aswell as on herbarium materials is necessary.For all practical purposes an illustrated simpleguide to identify the useful bamboos would beof great practical value since biologists ofvarious disciplines are interested in the pro-pagation, genetic improvement and multipleuse of bamboos.

The unique growth habit of bamboos andtheir fast growth rates provide an excellentopportunity to improve the biomass. This isvery important to many of the poorer coun-tries where forest resources are fast depletingand people are faced with many hardshipscaused by the lack of timber and fuel wood(Anon, 1980).

After the earlier work of Arber (1934),nothing much has been,done on the growth,structure, cytology and reproduction of bam-boos. Nevertheless the general interest inbamboos continues among the biologists ingeneral, and the foresters in particular. Theirobservations and reports are published fromtime to time (McClure, 1966). The first Sym-

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posium on Bamboos held in Singapore(sponsored by International DevelopmentResearch Centre of Canada) and the publica-tion of the proceedings therefrom is a signifi-cant contribution in this decade, updating theavailable information on bamboo research inAsia (Lessard and Chouinard, 1980). Mostof the papers published are country or statusreports emphasizing the need to increasebamboo production for economic gains.Some of the authors have clearly emphasizedthe urgent need for further basic research onbamboos that would help the conservation ofgenetic resources and the propagation ofsuperior bamboos in great numbers employ-ing both traditional and modern methods.

Due to a variety of reasons, the bamboosare difficult if not complex materials to workwith and hence the paucity of knowledge onmany basic aspects, including anatomy(Esau, 1965; 1977; Fahn, 1967; Cutter,1971). This paper is a brief report on certainanatomical characters of some wiId and culti-

vated bamboo species present in Singapore.

Materials And Methods

Large mature clumps of bamboo speciesare growing wild in the nature reserves as wellas the cultivated groups in Singapore BotanicGardens. Certain species like Bambusa uerti-cillate and other grass bamboos are also culti-vated in private gardens. About six generaand 23 species are locally present (Table 1).The following eight species are presentlyinvestigated: Bambusa pergracile, B. teres, B.tulda, B. vulgaris, Gigantochloa oerticillata,Schizostachyum brachycladum, S. jaculansand Thyrsostachys siamensis. The materialswere collected, photographed and therequired parts were fixed in FAA. ButyIalcohol series was used for dehydration. Theembedding of tissues, microtoming and stain-ing were carried out following the standardmethods (Sass, 1951).

Table 1. Bamboos growing in Singapore Botanic Gardens with Acquisition Numbers.

1. Bambusa dolichoclada. W. 260B.2 . B. glaucescens. W. 247.3. B. pergracile. W. 253.4. B. teres W. 252.5 . B. tulda W. 233.6. B. variegata. W. 271.7 . B. ventricosa. W. 232, W. 264A, W. 269, W. 275.8. B. vulgaris W. 243A, A. 260A, Y 95, Y 95A.9 . Dendrocalamus pendulus. W. 280.

1 0 . Gigantochloa apus. W. 254, W 277A, W 302.1 1 . G. naname. W. 278.12. G. verticillata W. 256B.1 3 . Phyllostachys sp. W. 248, W. 249.1 4 . Schizostachys brachycladum W. 231. W. 268, W. 277.1 5 . S. jaculans* W. 154, W. 243.1 6 . Thyrsostachys siamensis W. 215, W. 222, W. 237, W. 262, W. 277.1 7 . Bambusa arundinacea.1 8 . B. heterostachya.1 9 . B. ridleyi.20. B. oerticillata.2 1. Dendrocalamus strictus22. Gigan tochloa levis .23. G. ridleyi.

!" Used in the present study; easily accessible and ideally situated for growth studies. 17-23. less commonlyfound due to urbanisation.

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Observations

Morphological considerations: Bothtaxonomic and general descriptions are avail-able for the species mentioned in Table 1, andmany of them are commercially importantspecies (Gilliland, 1971; Holttum, 1958) Hence, these details are not repeated again.The healthy mature clumps of bamboosgrown in Singapore Botanic-Gardens areeasily accessible to study the growth charac-teristics. Due to the humid tropical climate thegrowth, in general, is non-seasonal and newshoots are produced all the year round. Insome species the growth is more profuse inthe post monsoon period of February-April.The fresh bamboo shoots are of varied sizesand shapes, all covered with compactlyarranged culm sheaths (Figs. l-8). The culmsheaths vary in size and shape depending onthe species examined (Figs. A-C). Theelongation of the axis or the culmcommences when the shoots are approx-imately 2-3 feet long, and the cone-shapedstructure becomes axial with distinct nodesand internodes. The culm sheaths are placeddistant apart due to internodal elongation andthey fall off after 120-160 days after the inter-node elongation begins. How long the bam-boo shoots would take, in terms of days orweeks, to emerge out of the soil surface andgrow further into culms is yet to be deter-mined. The bamboo clumps studied presentlyare more than 30-50 years old according tothe records maintained in the Gardens.Although most of the bamboo species grow inclumps there are certain variations amongthem. Some of the clumps are very densedue to heavy accumulation of debris, soil andrhizomes. Size, colour, length of internodesand formation of aerial branches are all vari-able. The basal part of the clump in certainspecies like B. pergracile, B. vulgaris is verywoody, dense and form thick rhizome plexuswhich appears as a raised platform of 2-4 feetabove ground and the dense culms emergeout of the thicket. In other species the begin-ning of each culm can be seen separately.The size, colour and the thickness of thegrowing axes vary among these differentspecies (Figs. A, B, l-4). Some of the axillarybuds at the mature nodes grow to form thelateral branches at the base of which manyroots are formed. The number of youngshoots formed from each bud is variable.

Unlike the culm sheaths, which are variable inshape and size, the lamina of the regularleaves are less distinctive at the species level.They are all dorsiventral structures and theirsizes vary in different species (Figs. l-8). Bothaxillary as well as accessory structures arecommon and the latter are more profuse atthe lower nodes developing into roots. Someof the axillary buds at higher nodes developinto lateral branches.

Shoot apices: The origin and develop-ment of shoots in woody monocots is uniquein many respects. The apices in most of themare conical (Fig. D, l-6). The apex of B.vulgaris is comparatively broader than others(Fig. D, 3). The developing leaf primordia arearranged more or less at the same transverselevel, protecting the shoot apex and contri-buting to the formation of abroad massivestructure (Fig. D, 3). In all of them the devel-oping leaves grow vertically and parallel tothe axis and cover the apex. The photographsin Fig. D, 1-6 are the general view of theapices taken at lower magnification showingapex, developing leaves and their arrange-ment as well as the gradual distinction seen inthe formation of nodes and internodes. Thecloser view of the shoot apices are shown inFig. E, l-8. The tissue organization in themconforms to the generalized angiospermpattern with regular tunica, corpus, peripheraland rib meristems (Fig. E, 1, 3, 5, 7). Thetunica consists of two well defined cell layersand they are distinctly seen in all the speciesinvestigated (Fig. E, 2, 4, 6, 8). The corpuszone is about six to ten layers deep below theinner layer of the tunica with many darklystained, isodiametric cells. The nuclei arelarge compared to cell size and contents. Thetissue below the corpus is highly meristematic.Active growth of this region results in the for-mation of more tissue towards the establish-ment of the stem axis (Fig. E, 2, 4, 6, 8). Thecorpus zone extends into the rib meristembelow and laterally into the peripheral meri-stem, the tissues of which are actively dividingand densely stained (Fig. E, 1, 3, 5, 7). Verymany prominent vascular strands are alsopresent. The rib meristem basal to the corpusdifferentiates into a very distinct intercalarymerisrem with many meristematic cell layers.The derivatives of these layers are added onbasipetally which enlarge and in sections thecentral part of the apex appears lighter incolour (Fig. E, 1, 3, 5, 7).

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The leaf primordia develop at the flank ofthe shoot apex and most of them form theleaf sheaths (Fig. E, 1, 3, 5, 7). Many of themhave a bigger or thicker base and the terminalpart ends as an attenuated structure. Majorityof the primordia have a knick or depression inthe middle and others split in the middle or atthe base (Fig. E, 1, 5, 7). The bamboo shootsare covered by a variety of sheath-like struc-tures that encircle the stem. The variousprimordia develop into culm shea ths ,sheath blades, ligules and other outgrowthson the iigules. Thus the apex as a whole is acentre of immense activity producing a largenumber of primordia that differentiate intomany varied structures subsequently (Fig. E,1,3,5,7).

From about the level of eighth to tenthnode the demarcation between nodal andinternodal regions becomes distinct. Thenodal plates appear as dark cross bars sepa-rating the lightly colaured internodal regions(Figs. D, E). The intercalary meristem at twonodes are enlarged (Fig. G, 8, 9). In the for-mer, the files of actively dividing cells are v e r yclear and neatly arranged. In the latter, whichis an older node the nodal plate has becomethicker with vascular strands traversing in dif-ferent directions. The intercaiary meristem isintact both below and above the nodal plates.The disintegration of cells making way for thehollow cavity is also in progress (Fig. G. 9).

Axillary buds: The bud primordia aredistinct and they can be distinguished fromthe leaf primordia even during early stages ofdevelopment. The latter develop aselongated, slender structures growing acrope-tally over-arching the main apex. in contrastthe primordia of the axillary buds are asym-metrical in outline since the growth is moretowards the leaf than on the stem side. Budsin different stages of development are shownin Fig. F, 1-6. Because of their sloping posi-tion the first prophyli formed towards the axisis shorter, somewhat triangular in outline andgrows parallel to the stem axis and the secondprophyl1 is longer, over-arches the apex andjoins the triangular structure. Both of themcover the developing apex (Fig. F, 5, 6). Themiddle part of the bud enlarges and the sub-sequent leaf primordia originate as lateralstructures. The apical region outgrows the pri-mordia and develops into a broad domeshaped apex. The apex of the axillary budalso shows a two-layered tunica and a regular

corpus region. The leaf primordia remainsmall and more than six to eight prophylis arepresent in certain buds. The first two pro-phylis formed would cover the bud for a longtime and these are well vascularised (Fig. F,6, 7). The subtending axial tissue below thebud undergoes a series of periclinal divisionsand many curved layers of meristematic tissueare present organising the shell zone (Fig. F,6). There is considerable variation in buddevelopment among the different speciesstudied. In B. teres and B. vulgaris, no budinitiation is seen even up to l0- 12 leaf stage.They seem to develop much later (Fig. F, 1,2). In others, such as G. vert ici l lata, S.jaculans, T. siamensis and B. teres the budprimordia develop much earlier (Fig. E, 1, 5,7). More number of apices cut both trans-versely and longitudinally need to beexamined to determine the early or late buddevelopment and their relative positions toone another. This is very important to corre-late the rate of shoot growth and the influenceof bud dominance in branching.

Structure of bamboo shoots: Theconical bamboo shoots were studied in detail(Figs. A, B, l-4). The young axis is sur-rounded by a number of culm sheaths andwhen these are removed one by one theyoung stem is exposed. In B. pergracile, B.vulgaris B. tulda and B. teres the conicalshoots are relatively massive when comparedwith other species (Figs. A, B, l-4). Thecentral cylindrical stem is relatively soft andeasy to section. The various regions of thestem axis were studied a) from the peripheryto the centre and b) from the tip to the base.

The cortical region shows a single layeredepidermis and the surface is usually coveredwith many epidermal hairs (Fig. G, 1, 2, 4).About two to three subepidermal layers alsoconsist of small cell layers followed by theground tissue in which the numerous vascularbundles of different sizes showing varyingstages of development are present (Fig. G, 2-5). In some, only groups of fiber cells are pre-sent with one, two or few vascular elements.Judged by the configuration and structure, itis clear that fiber cells develop early and thereis no synchronisation in development eitherbetween the vascular and non-vascular ele-ments or between the xylem and phloemtissues. Also the peripheral bundles of similarsizes show varied number or quantity ofxylem and phloem tissues. In contrast, the

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Figure F, 1-7. 1. LS. shoot apex B, teres showing development of leaf primordia. 2. L.S. shoot spex Thyrsostachyssiamensis. Note the elongated apex with many leaf primordia and a single axillary bud on r ight hand side of the axis. 3.7. L.S. apex of B. teres showing the development of axillary buds. The early prophylls arch over the apex and centralpart of the bud enlarges. well protected. The central dome and prophylls are well developed as seen in 6 and 7. Two-layered tunica and corpus are very clear in 7.

bundles in the centre are fairly uniform in sizeand contents (Fig. G, 6). Both proto andmetaxylem as well as phloem can be easilydistinguished. The sclerenchymatous capsseem to develop later. In general, it is clearthat the vascular bundle development is cen-trifugal. In B. teres there are many radialvascular strands extending from the periphery

to the cortex (Fig. 6). Since tissues for sec-tioning were taken at random from the differ-ent regions of the cone, no generalization canbe made on the sequential development ofvascular strands with regard to their relation-ship to the main apex or the nodes. It is poss-ible to establish the relative degree of tissuematurity in the massive, conical bamboo

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shoots with reference to the enlargement ofthe axis and the nodal positions. Similarly, acorrelation can also be established betweenthe vascular bundles that are present in theouter and inner cortical regions.

Culm sheath: The bases of culm sheathsare cut along with the tender main axis (Fig. G,4, 5, 7). The transections of these show dis-tinct structural variations between their outerand inner surfaces. As in the stem the outerepidermis consists of a single layer of cells withor without epidermal outgrowths. One or twosubepidermal layers differentiate into scleren-chyma. The rest of the mesophyll is undiffer-entiated and the cells increase in their sizetowards the inner epidermis. The vascularbundles are of different sizes and shapeseither oval or round (Fig. G, 4, 5, 7) coveredall round or partly by prominent sclerenchy-matous bundle caps. In the early stages ofdevelopment, the vascular bundles occupyalmost or more than half of the cross sectionalarea of the sheath. With subsequent develop-ment of the mesophyll, more towards theinner epidermis, the vascular bundles arerestricted more towards the outer epidermis(Fig. G, 5, 7). The inner epidermis is small,one-layered, distinctive with thickwalled cells.Facing the bigger bundles there is a group ofsmaller cells with characteristic thick wallsresembling collenchyma. Many of theenlarged mesophyll cells in T. siamensis hadtwo or more nuclei in them (Fig. G, 7).

Stem structure: The aerial stems of thedifferent species studied show the monocottype of stem anatomy with a distinct epider-ma1 layer, ground tissue and big vascularbundles (Figs. H, 2, 6, 8; I, 1, 3). In S.jaculans the epidermis is more prominentthan in others- with enlarged cells, with threeto four layers of smaller subepidermal cellsthat develop later into regular sclerenchyma(Fig. H, 8). in other species, the subepi-dermal scierenchyma is formed early (Figs.H. 2, 6; I, 3). The ground parenchyma ishomogeneous in nature with cell size increas-ing centrifugally. Additional enlarged cellgroups surrounding the vascular bundles aredistinct in certain species like S. jaculans andB. pergracile (Fig. H, 1, 8, 9) These celllayers may develop into thick sclerenchyma atsubsequent stages. The smaller bundles arearranged nearer the periphery and the largerbundles are towards the centre. The vascularbundles are collateral with sclerenchyma

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sheaths or caps present either in two or threegroups.

In most of the cases, only young stems areused and obviously the distinct fiber strands orcaps are yet to develop. The pith cavity for-mation is distinct in B. vulgaris, S. jaculansand T. siamensis (Figs. H, 6; I, 1, 2). Thestem structure of B. teres is shown in detailwith both the peripheral and central part ofthe axis with intact perenchyma (Fig. H, Z-5).Within the central part there are two distinctvascular bundles, slightly smaller in size thanthose present in the inner peripheral region.The arrangement of the vascular tissues inthese two medullary bundles is similar tothose in the peripheral region. The demarca-tion between the peripheral and centralregions is also clear (Fig. H, 3). Another veryinteresting detail is that most of the enlargedpith cells have two or more nuclei in them(Fig: H, 4, 5). In B. vulgaris the innermost celllayers adjacent to pith are somewhat thick-walled and very distinct almost appearing as aborder zone (Fig. H, 6).

Root structure: As seen in transversesections, the young roots show a number ofepidermal hairs, fairly straight and majority ofthem are uninucleate (Fig. 1, 5). Below theepidermis there are. three to four layers ofsclerenchyma followed by a uniform region ofparenchyma. The stelar structure is typicallymonocotyledonous with regular endodermisand distinct vascular groups of xylem andphloem. Many large air spaces are presentboth in cortex and the stelar regions whichseem to be a common feature in manygrasses. In the older roots the hairs are slightlythicker and many of them have small kinksand curved outlines. In a few cases even thebranching of root hairs is seen (Fig. I, 6, 7).

Root hairs are simple epidermal out-growths, commonly formed on young roots,showing very few or no abnormalities in theircell morphology. Very few cases are knownwhere the root hairs are actually branched(Rao and Chin, 1972). Such details are dis-cussed mostly in relation to certain dicots andthis seems to be the first instance for mono-cots and especially the bamboos (Rao andChin, 1972).

The structure of rhizome and root systemis important since they are adaptable to avariety of soil conditions and prevent soilerosion. In many ways they are much more

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efficient than the grasses which are the earlycolonisers of the cleared or open land.

Leaf structure: Leaves in the familyGramineae are specialised structures. Manyof them are primarily the protective structurescovering the growing parts of t h e rhizome,shoot apices and axillary buds. The rhizomesheaths are simple, triangular in outline withsmall pointed ends and near the apex themargin is sometimes serrated. The structurethat covers the bamboo shoots and youngstems are the culm sheaths which havesmooth, adaxial and rough abaxial surfaces,the latter surface covered with many types ofepidermal outgrowths including hairs (Fig. C,l-3). The culm sheath is also triangular in out-line and the basal part is broad with a narrowterminal part (Fig. C, l-3). Distinct Iigule andauricles may be present at the point where thebroad base slightly narrows down to form thetriangular structure (Fig. G, 9-l 1). The thirdstructure is the foliage leaf with the basalsheath or a petiole and a regular lamina.

The transections of the lamina in differentspecies reveal an upper epidermis, two orthree layers of mesophyll with or without adistinct palisade layer, fairly large air spaces,lower mesophyll and lower epidermis (Fig. J,1-13). The upper epidermal layer is more dis-tinctive than the lower with groups of bulli-form cells which are bigger in certain speciesthan in others (Fig. J, 4. 5, 8. 10. 12). Thegroups of bulliform cells alternate with airspaces. The cuticle is thick on both the layersand in many of them like B. teres, B. tulda,B. vulgaris and G. verticillata the cuticle onlower epidermis is papillate (Fig. J, 3, 5, 8).In S. brachycladum the palisade layer is muchmore prominent. The plicate or lobed condi-tion is common in many of the outermesophyll layers. At places where either airspaces or the bulliform cells are present theupper palisade is restricted to a single layer.The second layer is represented by a group oftwo or four cells that form a bridge intercon-necting the upper mesophyll with the lower.The size and extent of air spaces are also vari-able (Fig. J. 1. 2. 4. 6, 7. 9, 11. 13). In B.tulda, G. verticillata and S. jaculans the pro-minent intercostal ridges are occasionally pre-sent and these form regular hump-like struc-tures and each one of these consists welldeveloped sclerenchymatbus tissue (Fig. J. 9.11). Both the number and the size of bulli-form cells increase between these groups of

sclerenchymatous humps. The vascularbundles in the leaves show the regular mono-cotyledonous structure and a group of scler-enchymatous cells interconnect the vascularbundles with upper and lower epidermis (Fig.J, 3, 10, 12). Stomata are commonly presenton the lower epidermis and in leaf transec-tions the guard cells appear smaller than theepidermal cells and devoid of papillate out-growths or thick cuticle (Fig. J, 3, 5, 12).

Discussion

The well known work on bamboos byMcClure (1966) summarises the basic workdone until 1960s. A critical survey of litera-ture. however reveals the fact that by andlarge the basic botany of bamboos is yetto- be worked out and recorded in a pro-per manner. The literature available at pre-sent is fragmentary, scattered and inadequateand the reasons are not too difficult to under-stand. Like in other aspects of tropical plants.whether wild or cultivated, there is very littleeffort made to study them well by the localscientists. Lack of trained manpower isanother problem. Only taxonomic studies arefairly complete and here again, there is nowell illustrated simple guide, easy to use bythe common man or others not familiar withtechnical terms.

More specifically, as it refers to the presentstudy, it was very revealing to note that thereis hardly any good paper describing theanatomy of bamboos. The list of referencesgiven by McClure (1966) and in the proceed-ings of the last workshop on bamboos in Asiawould substantiate the above statement.Standard recent reference works on plantanatomy (Esau. 1977; Fahn. 1967; Cutter.1971) or even some of the older works(Goebel. 1930; Eames and McDaniels. 1947;Eames. 1961) do not provide much informa-tion due to the lack of any anatomicalresearch. The recent papers published byother Asian or German botanists are noteasily available since they are in local jour-nals. As stated before. bamboo anatomyis hard to work since most of the structuresprovide a good challenge to microtomy andthe structures are relatively difficult to inter-pret. even though many other grassesincluding the various cereal crops are fairlywell studied. Another reason for this inade-

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Figure J, X-13. Leaf transections as seen under low and high magnifications. 1. B pergracile. 2. 3 B teres 4, 5 Btulda 6, 10 S . brachycladum 7. 8, B vulgarIs 9 G, uerticillata. 11 S. jaculans 12, 13. T siamensis the upperand lower epidermis are distinct in all with bulliform cells on the upper and stomata on the lower Sc le renchyma humps areformed in some as seen in 9 and 1 1 Bundles are connected with epidermis by sclerenchyma pegs

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quacy in our knowledge is the generalassumption that all is well with bamboos andthey grow well naturally or in plantation. Onlyrecently when the natural supply is runningshort or inadequate to meet the needs of theincreasing population there is a renewedinterest in increasing bamboo production. Forthe same reason, two international work-shops have been conducted within a period offive years.

Perhaps there are no other single group ofplants that display so many variable vegeta-tive characters as bamboos and our know-ledge about the developmental aspects ofthese is very limited.

The general organisation of shoot apexconforms to the pattern well known in angio-sperms and there is only one earlier study onSinocalamus ( = Bambusa) beecheyana, dis-tributed in China (Hsu, 1944). This work isnot quoted in other works or easily missed forreasons unknown. The axillary bud develop-ment takes place early in the second or thirdleaf axils which is different from the majorityof the species studied presently.

The shoot apex in woody monocotyle-dons is very interesting as recorded in thecase of palms (Ball, 1941; Tan and Rao,1980). The primary thickening meristemcharacteristic of palms (Ball, 1941) is absentin bamboos. The prominent tissues of the flankregion, commonly seen in palms is seen pre-sently only in case of Bambusa vulgaris. Thedifferentiation of many procambial strandsand the prominent peripheral meristem aresimilarities noticed between palm and bam-boo shoot apices. The plicate leaf conditionseen in other monocots is absent in bamboos(Periasamy, 1980).

Some of the bamboo shoots are verymassive structures and they are very richlyvascularised as evidenced by the formation ofvascular strands. A detailed anatomical studyto show the differences between the hardmature culm and the soft tissues in the bam-boo shoots would be interesting and so alsothe node and internode developmentbetween the young bamboo shoots emergingat the ground level and the aerial woodculms. The environmental conditions underwhich these two develop are totally different.

The morphogenesis of different kinds ofaxillary buds, single or multiple, or those that

give rise to leptomorph or pachymorph rhi-zomes will not only be very interesting tounderstand the growth habits of bamboos butalso would help to improve their propagationby vegetative cuttings,

The stem structure is relatively wellstudied and four types of vascular bundles arerecognised which also lend support to the sys-tematics of the group (Liese, 1980; Holttum,1958). The materials studied at present camefrom young stems and the number of scleren-chymatous caps or groups could not beclearly determined for this reason.

The bamboo leaf structure is similar tothose of other grasses with characteristic bulli-form cells, presence of larger air spaces andbig vascular bundles with characteristic bundlesheaths (Esau, 1977). Many of these detailsare also recorded presently. The structuralvariations noticed between regular leaves andculm sheaths are interesting especially the dif-ferences in mesophyll and the nature ofvascular bundles. Whether these differencesare present in all the bamboos is yet to bedetermined and different types of sheathingorgans should be studied in detail. The mor-phogenesis of different types of leaves will beinteresting both from the descriptive andexperimental points of view. It closelyresembles heterophyllous condition since thesame axis from rhizome to fleshy shoots tostrong aerial axes produce three differenttypes of foliar structures. This is an interestingproblem to work with.

As an outcome of the previous workshopmeeting in Singapore several importantresearch needs and priorities were identifiedand recommended. Very briefly these includethe following: a) Studies on culm anatomy todetermine or correlate the strength and struc-tural properties. b) Detailed studies on bam-boo fibres. c) Factors responsible for naturalregeneration in bamboos. d) Identifying theeasily recognisable vegetative characters. e)Propagation by tissue culture and shoot cul-ture for mass production and germplasmexchange. f) To use the juvenile tissues on theculm for large scale propagation. followingthe experiences gained in sugarcane. g) Toidentify very easy methods for vegetative pro-pagation so that the bamboo industry can berevolutionised. h) Increasing the quantity ofpropagules/hectare. i) More frequent use ofbud material for in vitro studies and a few

224

others. The papers presented in the secondworkshop have provided a few or someanswers and indicators to solve some of theproblems posed earlier.

With the number of papers presented inthe form of valuable contributions towardsimproving the quality and quantity of bam-boos in Asia and with different suggestionsmade, we are now in a better position to planfurther activities to achieve the objectives laiddown. Foremost is the need to improve thebasic work on bamboos and here we have touse the existing expertise in different countriesso that no time or money is unnecessarilywasted by repeating the same research in fouror five countries simultaneously, unless thenature of the problem is such that it needsattention by different people in several labora-tories. Several models are already availablelike Asian Mangrove project supported byUNDP and others. Under this project bothtraining and research programmes areincluded with the main objectives of improv-ing the trained manpower for specificresearches. Wherever possible, the skills ofthe staff already working need to beimproved. New staff should be technicallytrained to work on bamboos. Improvement ofbamboos in Asia can be launched as an inter-national project and the different activities canbe coordinated by one or two persons. Anymoney, manpower and efforts spent in thisdirection will pay rich dividends in the nearfuture.

For many of the big world organisationssuch a project may be a very insignificant oneand they may not have the necessary man-power which means establishing a newsection to manage the project. By launching anew medium-sized project for three or fouryears many of such cumbersome procedurescan be avoided which would also bring thedesired results within a shorter period of time.Hopefully the benefits derived can be sharedby all and many of the needs of poor ruralpeople can be easily met.

Acknowledgements

I am grateful to Dr C B Sastry , IDRC,Singapore for inviting me to participate in theworkshop meeting; to my colleagues MrJohnny Wee, Mr Ong Tang Kwee and MdmChan Siew Khim for their technical help and

the National University of Singapore for theaward of research grant FSOF 3/80 underwhich this work has been carried out.

References

Anon, 1980. Firewood crops. NationalAcademy of Sciences, Washington,D.C., USA.

Arber, A. 1934. The Gramineae. CambridgeUniversity Press, Cambridge.

Ball, E. 1941. The development of the shootapex and the thickening meristem. Amer.Jour. Bot. 28: 820-832.

Cutter, E. 1971. Plant Anatomy: Experimentand Interpretation. Addison-Wesley,London.

Dransfield, S. 1980. Bamboo taxonomy inthe Indo-Malesian region. 121-130. In:Proc. Workshop on Bamboo Research inAsia, Singapore. (Eds.) G. Lessard andA. Chouinard. IDRC, Ottawa, Canada.

Eames, A.J. 1961, Morphology of the Angio-sperms. McGraw Hill, New York.

Eames, A.J. and MacDaniels, L.H. 1947. AnIntroduction to Plant Anatomy. McGrawHill, New York.

Esau, K. 1965. Plant Anatomy. John Wiley& Sons, New York.

Esau, K. 1977. Anatomy of Seed Plants.John Wiley & Sons, New York.

Fahn, A. 1967. Plant Anatomy. PergamonPress, Oxford.

Gilliland, H.B. 197 1. Grasses of Malaya.Govt. Printing Press, Singapore.

Goebel, K. 1930. Organographie derPflanzen. Gustav. Fischer, Jena.

Holttum, R.E. 1958. Bamboos of Malaya.Gdns. Bull. (Sing.) 16: l-35.

Hsu, J. 1944. Structure and growth of theshoot apex of Sinocalamus beecheyanaMcClure. Amer. Jour. Bot. 31: 404-411.

Lessard, G. and Chouinard, A. 1980. Bam-boo Research in Asia. IDRC, Ottawa,Canada.

Liese, W. 1980. Anatomy of bamboo. 161-164. In: Proc. Workshop on BambooResearch in Asia. Singapore. (Eds.) G.Lessard and A. Chouinard. IDRC,Ottawa, Canada.

225

McClure, F.A. 1966. The Bamboos. HarvardUniv. Press, Cambridge, USA.

Periasamy, K. 1980. Development of leafpiication in non-palms and its relation towhat obtains in palms. 108-116. In:Proc. Intl. Symp. Histochemistry, Devel-opmental and Structural Anatomy ofAngiosperms. Madras University, P & BPubl. , Trichy, India.

Rao, A.N. and Chin, S.C. 1972. Branchedand septate root hairs in Melastomamalabathricum. Cytologia 37: 111-118.

Sass, J.E. 1951. Botanical Microtechnique:Iowa State College Press, Ames, Iowa,USA.

Tan, K.S. and Rao, A.N. 1980. Certainaspects of developmental morphologyand anatomy of oil palm. 266-285. In:Proc. Intl. Symp. Histochemistry, Devel-opmental and Structural Anatomy ofAngiosperms. Madras University. P & BPubl., Trichy, India.

Willis, E.J. 1951. Dictionary of FloweringPlants. Cambridge Univ. Press, Cam-bridge.

226

Observations on VascularBundles of Bamboos Native to China

Jiang Xin and Li Qion*

Sichuan Agricultural College, China*Yaan High School, China

Abstract

The arrangement of vascular bundles,presence or absence of cortical air spaces, theextent of parenchyma between the bundlesare used as the important criteria in thepresent study of bamboo types. About 45species of 10 genera are classified under fourmajor types.

Using vascular bundle arrangement as thecriterion in leptomorph rhizomes* of bam-boos, ten genera and 45 species of bamboosnative to China can be classified into the fol-lowing four major types:

Type I Vascular bundles are separated byparenchyma.

(A) No air canals in cortex (Fig. 1). Bam-boos of this type are the following:- Phyllo-stachys arcana, Ph. aurea, Ph. aureosulcata,Ph. bambusoides, Ph. bambusoides var.tanakae, Ph. bambusoides var. castilloni, Ph.bambusoides var. castilloni-inverssa, Ph.besseti, Ph. decora, Ph. dulcis, Ph. flexsuosa,Ph. glauca, Ph. glauca f. yunzu, Ph. meyeri,Ph. nigra, Ph. nigra var. henonis, Ph. nuda,Ph. nuda f. localis, Ph. viridis, Ph. platy-glossa, Ph. praecox, Ph. prapinqua and Ph.pubescens.

Phyllostachys nigra var. henonisFig. 2. Phyllostachys robvstiramea.

l Leptomorph rhizomes are the same as monoaxial and amphiaxial rhizomes. In China the bamboo rhizomes aredivided into three kinds, moaoxial, amphiaxial and sympodial rhizomes

227

Fig. 3. Indocalamus victorialis,

Fig. 4. Pleioblastus amarus.

(B) Air canals are present in cortex (Fig.2). Bamboos of this type are listed as follows:PhyllostAchys robustiramea.

Type II Vascular bundles are isolated.Between them, there are fibres - cell groupsin rectangular, round, or variant forms, andthey are never linked. These are mostly peri-pheral in position. No air canals in cortex(Figs. 3 and 4). Bamboos characteristic of thistype are as follows: Indocalamus longiauritus,1, victorialis, Pleioblastus amarus, P I .gramineus, PI. sp., PI. sp., Psudosasa amabilisand Sinobambusa tootsik.

Type III Vascular bundles are linked,occasionally with very narrow gaps of paren-chyma interrupting Air canals in cortex (Fig.5). This type includes: Phyllostachys hetero-clada and Ph. nidularia. ,

Type IV Vascular bundles are connectedin the form of a ring enclosing stele.

(A) No air canals in cortex (Fig. 6). Bam-boos of this type are as follows: Arundinariafargesii, Chimonobambusa utilis, Ch. qua-drangular&, Ch. purpurea, Qionzbuea lumidi-noda, Sasa unbigena and Sinarundinariafangiana.

I ; I . i n

Fig. 5. Phyllostachys heteroclada.

Fig. 6. Chimonobambusa utilis.

(B) Air canals in cortex (Fig. 7). Bamboosof this type are: Chimonobambusa sze-chuanensis and Qionzhuea opienensis.

Fig. 7. Chimonobambusa szechuanensis.

Observations have shown that there is cor-relation between vascular bundle arrangementmentioned above and with the other vegeta-tive characters of a species. These are usefulcharacters in classification and identification.

229

A Study on the Anatomy of the VascularBundles of Bamboos from China

Wen Taihui and Chou Wenwei

Zhejiang Bamboo Research Centre, China

Abstract

This paper provides anatomical details ofregular vascular bundles of the culms of 28bamboo genera with 100 species and fivevarieties from China, The characteristics ofthe vascular bundles from the outer wall tothe inner wall are also illustrated for certainspecies and this data helps to show thedifference between the consanguinity of thecharacteristics and morphology of thevascular bundles of bamboos of each genus.It also provides valuable reference for iden-tifying bamboo material, articles made of bam-boos, relics and fossils.

The paper also describes a simple methodofpreparing and examining the cross sectionalsurface of bamboos. The method is con-venientfor use infield examination.

The vascular bundles are categorized intofive types, that is, the double broken type,broken type, slender-waist type, semi-opentype and open type.

Variations in vascular bundles and theirusefulness are mentioned.

The anatomical characteristics of the culmvascular bundles are an important supple-ment to the classification of bamboos andappropriale examples are given.

The variations in distribution and anatom-ical characters of Indocalamus and Sasaare discussed. The vascular bundles of Sasa(inclusive of Sasamorpha) are all semi-openwhile those of Indocalamus are mostlyopen type. The arrangement of the vascularbundles of the genera is as follows: Indo-calamus: undifferentiated - semi-differ-ent ia ted - semi-open - open. Sasa(including Sasamorpha): undifferentiated- semi-differentiated - semi-open.

230

Introduction

Anatomy of the vascular bundles of bam-boo culm is a useful guide for bamboo tax-onomy. The details can be used when somebamboos cannot be identified with theirflowers. It is also used in identifying somebamboos from ancient cultural relics. Inaddition, the anatomical details will help todetermine the splitting property, strength andthe ratio of fiber strands of bamboo culm usedby modern papermaking industry, handicraftindustry and other bamboo processing indus-tries. This article introduces a simple methodfor examining culm vascular bundles by usingonly a saw, a knife and a magnifying glass.First cut a culm into three sections, the upper,the middle and the lower part, then smooththe cut with a sharp knife and smear it withwater. This will make the vascular bundlesvisible, if seen through magnifying glass.Bamboos can be identified on the basis ofcharacteristics and features, arrangementsand types of the vascular bundles. If thecross-sectional area of vascular bundlesheaths and the fiber strands are larger, thenthe bamboo wood is strong and contain ahigh percentage of fiber. If the vascularbimdles are evenly distributed the bamboowood has a good splitting property.

Materials and Methods

The plant materials used in this study in-cluded 99 species and 5 varieties belonging to28 genera collected between 1976 and 1983in Zhejiang, Fujian, Guangdong, Yuennan,Jiangxi, Shichuan provinces in China. Eachbamboo culm was cut into three sections, the.upper, middle, and the lower part, about 0.2-0.3 mm thick taken from 5 cm beyond culm

nodes with a sharp knife. After being wetted,the section was observed under a micro-scope, 8 x 15, with a tessellated scale in itseye piece, and the figure was drawn on tessel-Iated paper to the scale. Other techniques likemicrography and tracing were also used.

Serial of the vascular bundles from thesections on the outer wall to the inner wall of3 segments were drawn, so that it could bewell seen from the drawing, size and arrange-ment of the vascular bundles.

Collection of plant materials.

Test No. Scientific Name Place of Col lec t ion

2-1. 1 .2-1 2.2-1. 3.3-1. 4.3-l. 2.3-l. 3.2-2. 4.2-2. 5,2-2. 6.3-1. 5.3-1. 7 .2-3. 7 .3-l. 9 .3-l. 1 0 .3-l. 1 1 .3-l. 1 2 .3-l. 1 3 .3-l. 1 4 .3-1. 15.3-l. 1 6 .3-l. 1 7 .2-3. 8 .3-l. 1 9 .3-1. 20.3-l. 21.3-1. 22.3-1. 23.3-l. 24.3-2. 25.3-2. 26.3-2. 28.3-2. 27.2 - 3 . 9 .3-2. 29.3-2. 322-4. 1 0 .2-4. 1 1 .2-4. 1 2 .3-2. 35.3-2. 33.3-2. 34.2-4. 1 3 .

2-5. 1 4 .

Thyrsostachys s iamensis GambleOxytenanthera nigrocilliata MunroGigan toch loa ligulata GambleDendrocalamus brandissi KurzD. giganteus MunroD. patellanis GambleD. strictus NeesD. latiflorus MunroNeosinocalamus affinis (Munro) Keng f.N. d i s t eg ius (Keng & Keng f.) Keng f. & Wen, ined.N. beecheyanus (munro) Keng f. & Wen, ined.Lingnania chungi i McClureL. wenchouens i s Wen.Bambusa basihirsuta McClureB. breviflora MunroB. dolichomerithalla HayataB. eutudoides McClureB. g ibbodes L inBambusa glaucescens (Wi l l ) S ieb .B. glaucescens var . shimadia (Hayata) Chia ex ButB. nana RoxbB. pervariabilis McClureB. text i l i s McClureB. text i l i s var . albo-stricta McClureB. text i l i s var . glabra McClureB. pachinens is var . hirsutissima (Odash. ) LinB. tuldoides MunroB. vulgris SchradB. subtr imcata Chia ex FungB. lapidea McClureB. oldhami MunroB. pras ina WenDinoch loa utilis McClureD. orenuda McClureCephalostachyum fuchsianum GambleC. pergracile MunroMelocanna humils KurzSchizostachyum pseudolima McClureS. funghomii McClureS. x inwuensis WenS. hainanensis Merr .Ampelocalamus act inotr ichus (Merr . & Chun)Chen. Wen ex ShengChimonocalamus pa/ lens Hseuh ex Yi

231

Yunnan XishuangbannaYunnan XishuangbannaYunnan XishuangbannaYunnan TengchongYunnan XishuangbannaYunnan MangshiYunnan XishuangbannaFujian Fu t ingZhej iang dinghaiYunnan KunmingFujian XiamenZhej iang DinghaiFujian Fu t ingZhejiang DinghaiZhej iang DinghaiZhej iang DinghaiZhej iang DinghaiZhej iang DinghaiZhej iang XunanZhej iang LinhaiZhe j iang Pu j iangZhej iang DinghaiZhej iang Wenl ingZhejiang XiamenZhej iang DinghaiZhej iang DinghaiFujianYunnan KunmingZhej iang DinghaiZhej iang DinghaiZhej iang DinghaiZhej iang FingyangGuangdon HainanGuangdon HainanYunnan MangshiYunnan XishuangbannaFujian XiamenYunnan LuxiYunnan XishuangbannaJiangxi XunwuJiangxi XunwuGuangdon Hainan

Yunnan J inp ing

3-2. 27.4-3. 31.2-5. 15.3-2. 39.3-2. 40.3-2. 41,3-2. 42.3-2. 44.2-5. 16.3-2. 46.3-2. 45.3-2. 47.3-2. 48.5-2. 81.4-2. 23.5-2. 83.5-2. 80.4-1. 17.5-l. 50.5-l. 51.5-l. 63.5-l. 60.5-l. 54.5-1. 52.5-l. 57.5-1. 55.5-l. 56.4-l. 18.5-1. 58.5-l. 624-1. 19.4-2. 20.5-2. 71.4-2. 21.5-2, 70.5-2. 72.5-1. 66.5-l. 67.4-2. 22.5-2. 74.5-2. 75.5-2. 76.5-2. 77.4-2. 25.5-2. 86.5-2. 87.5-2. 88.5-2. 895-2. 90.4-3. 26.5-2. 92.5-2. 93.4-3. 27.

C. f imbr ia tus Hseuh ex YiFerrocalamus strictus Hseuh ex YiFargesia farcta Y iFargesia ampullaris Y iF. chungii (Keng) Wang ex YiF. grossa YiF. se tosa YiF. edulis YiYushania n i i takayamensis (Hayata) Keng f.Y. hirticaulis Wang ex YeY. wixiensis YiY. hasihirsuta (McClure) Wang & YeY. confusa (McClure) Wang & YeChimonobambusa quadragularis MakinoC. setiformis WenC. conoo l ta Dai ex TaoC. armata (Gamble) Hsueh ex YiIndosasa crassiflora McClure1. sinica Chu & Chao1. s h iba taeao ides McClureI . g labra ta Chu ex ChaoS inobambusa in t e rmed ia McClureS i n o b a m b u s a rubroligula McClureS . edu l i s Wen

.

S. glabrecens WenS. nephroaurita Chu ex ChaoS . too t s i k var. Ieata (McClure) WenS . too t s i k MakinoS . anaur i ta WenS . g igan teus WenSemiarundinaria lubrica WenBrachys tachyum densiflorum KengPhy l lo s tachys u i r id i s (Young) McClureP. heterocycla (Carr.) MatsumPhyl los tachys praecox Chu ex ChaoP. stimilosa Zhou et LinP. heteroclada Oliv.P. r u b r o m a r g i n a t a McClurePseudosasa amab i l i s (McClure) Keng g .P. longiligula WenP. contori (Munro) Keng f.P. o r tho t ropa Chen ex WenP. no ta ta Wang ex YeP l e i o b l a s t u s a m a r u s (Keng) Keng f.PI. ch ino MakinoPI. ovatoauritus Wen, inedPI . h i s iaenchuens i s WenPI. kwangsiensis HsiungPI . matsuno i (Makino) NakaiPI. gramineus (Bean) NakaiPI. o l eosus WenPI. maculatus (McClure) Chu ex ChaoClau inodum bedogona tum (Wang et Ye) Wen

Yunnan LuxiYunnan J inp ingYunnan LuxiYunnan LuxiYunnan Mongsh iYunnan L i j i angYunnan ZhongdianYunnan KunmingZhej iang LinanJiangxiYunnanFujian C h o n g a nJiangxi HuanganFujian SanminFujian WuyishanYunnan LuxiGuangxi LuyeGuangxi NanningYunnan HekouGuangxi Gui l inFujian WuyiSichunan ChangningGuangzhouYunnan MalipoZhej iang QinguanGuangxi quangzhouFujian anxiFujian anxiJiangxi J ingangshanZhej iang LongquenZhej iang LongquenZhej iang J inghuaZhejiang Lin haiHangzhouZhej iang LinhaiZhej iang LinhaiZhej iang LinhaiZhe j iang LuoqingJiangxiGuangxi QuanzhouGuangzhouZhej iang TaishunFujianFujian J ianyangFujian XiamenZhej iang LuoqingZhej iang QingyuanZhe j i ang Yong j i aFujian ShanghangGuangzhouJiangxi FongxingFujian J iang ouJ iangxi Wuyishan

232

Test No. Scientific Name Place of Col lec t ion

4-2 . 24 . Ol igos tachyum sulcatum Wang ex Ye4-3. 28. Indocalamus tessellatus (Munro) Keng f.

Fujiang MingqingZhejiang qingtin

5-2 . 98 . I. Iongiauritus Handel-Mazz5-2 . 97 . I. Iatifolius McClure5-2 . 96 . I. mo g o i (Nakai) Keng f.4-3 . 29 . Gel idocalamus stellatus Wen5-1 . 64 . Sasa q ingyuanens i s Hu4-3 . 30 . S. sinica Keng

Variations in the VascularBundles

The vascular bundle includes both theconducting tissue and the mechanical tissue.Joining up the plant parts, the undergroundrhizomes and the upper leaves, as a whole,the vascular bundles transport nutrientsolution by vessels and sieve tubes. Becauseof the large size of the bamboo plant the con-ducting tissue is reinforced by an outsidemechanical tissue which may facilitate circula-tion.

Some species even have one or two fiberstrands. The sectional area of these fiberstrands is usually greater than that of thecentral vascular bundle. The parenchyma inthe vascular bundles serves as a buffer zonecontributing to the elasticity of the culms,without which the culms would be inflexibleand brittle. Near the epidermis, there are gen-erally one or two layers of fiber bundles,closely arranged giving mechanical strength.These are followed by one to three layers ofsemi-differentiated vascular bundles withincipient conducting tissue. Further inside areregular vascular bundles, generally in thecentral part of the culm section, two to ten innumber.-The shape and arrangement of thevascular bundles near the inner wall are irre-gular, and the position of sclerenchymabundle sheath varies from sideward to out-ward or inward.

Although the morphology of the vascularbundle varies a lot, it remains relatively stablewithin a given internode of a species.

The Evolution of the VascularBundle in Sympodial Bamboos

Sympodial bamboos are said to be com-

Jiangxi DaiyuJiangxi XunwuFujian WuyishanJiangxi DaiyuZhej iang QingyuanZhej iang Linan

paratively primitive with wide range of dif-ferentiation. Based on vegetative charactersthe sympodials are divided into two groups,sympodial rhizomes with short necks (clump)and long necks (spreading). The formerinclude genera Thyrsostachys, Dendro-calamus, Lingnania, Bambusa, Ampelo-calamus and Schizostachyum, and the latterChimonocalamus, Fargesia, Yushania.Melocanna, Pseudostachyum etc. Theinflorescences are indeterminate as inBambusa, Dendrocalamus, Lingnania,Thyrsostachys and determinate in Ampelo-calamus, Chimonocalamus, Fargesia,Yushania etc. The anatomical details of thevascular bundles reflect the main evolutionarytrends.

The sympodial genera that possess thedouble-broken and broken types of vascularbundle are Thyrsostachys, Dendrocalamus,Lingnania, Bambusa, Schizostachyum,Gigantochloa, Oxytenanthera, Neosino-calamus etc.

Schizostachyum, Cephalostachyum,Melocanna are sympodial but taxonomistsusually do not treat them as the same, butgroup them separatly as a tr ibe namedMelocanneae or Schizostachyeae. This clas-sification of a sub-tribe can be justified since allthese genera have the bundles which