MORPHOLOGICAL AND ANATOMICAL STUDIES ON THE WHITE MANGROVE

[AVICENNIA OFFICINALIS L.]

Dissertation submitted to the Mahathma Gandhi University, Kottayam, in partial fulfillment for the

Degree of Bachelor in Science.

By,

DIVYAMOL.P.KReg No: 351123

Department Of Botany,Sacred Heart College,

Thevara,Kochi-682013.

2006-2009

CONTENTS

1. Introduction and Review of Literature

2. Materials and Method

3. Observation and Discussion

4. Summary

5. Plates

6. References

CERTIFICATE

This is to certify that the dissertation entitled “Morophological and

Anatomical studies on the white mangrove [Avicenna Officinal is L.]. Submitted

here with contain the results of bonafied project work carried out by

Miss. Divyamol P K, under my supervision. This dissertation is submitted in

partial fulfillment of the requirement for the award for the degree of Bachelor of

Science (Botany) to M.G. University.

Thevara Dr. M.S. FrancisFebruary 2009 Supervising Teacher Department of Botany Sacred Heart College Thevara

ACKNOWLEDGEMENT

I am grateful & deeply indebted to Dr. M.S. Francis Department of Botany, S.H.

College, Thevara, for his sustained guidance and encouragement throughout the course of

my project work & for providing all the necessary facilities for this work.

I extant my grateful to Dr. V.J. Dominic, Head of the Department of Botany, S.H.

College, Thevara, for providing all the facilities necessary for this work. I wish to

acknowledge the authorities of Library of college facilities and timely help.

I also sincerely thank all the teaching staff and non touching staff of the

Department of Botany who helped me during different stages of this work. My sincere

thanks to all my friends, who have helped me in this attempt in one way to other.

Thevara, Divyamol P.K

February 2009 Reg No: 351123

Chapter: 1

INTRODUCTION & REVIEW OF LITERATURE

Mangrove is a West Indian name given to formation of trees and shrubs

inhabiting the coasts and river estuaries of tropical or subtropical seas. Plants

occurring in mangrove vegetation belong to several families. The term mangrove

is derived from Portuguese and English words Viz “Mangue” in Portugal where as

the community of trees and the bushes are known as ‘grove’ in English. The

mangroves may be defined as the coastal tropical forest formation encircled or

spread over by the tidal rivers or the seawater, flooded or bathed frequently.

Mangrove plants and the mangrove ecosystem or the mangal in totality are

most important in the perspectives of its economic potentialities, as mangroves

provide ideal habitats for economic species of fish, shrimps, prawns, crabs and

good number of threatened, rare and endemic but most important species of

aquatic and terrestrial fauna. All these coastal or estuarine vegetation along with

its dense growth and wide spreading habitat. Play physical support and protective

role in these fragile coastal estuarine zones in the tropical and subtropical

countries in the globe; in general and in the Indian mangals in particular Bio-mass

from the mangrove plants continuously supply nutrients to coastal, estuarine and

offshore aquatic environment resulted healthy environment and also raised or

maintained productivity of the important water phases. Besides these mangrove

timber and mangrove wood have immense value in carpentry work and as fuel

wood to the rural people of Sundarbans (Naskar, 2002).

Mangrove plants are very commonly found on some saline soils of

Indogangetic plains in Western India, near the sea coasts of Mumbai and Kerala,

in the banks of Gaumati and Godavari in South India, particularly in the region

where rivers meet the ocean and in Andaman and Nicobar Islands.

Mangrove forests grow near the estuaries or the deltas of rivers, swampy

margins of Islands and along sea coasts. The soil is formed of silt, silt–loam or silt–

clay and sand. The plants are typical halophytes which are characterized by

presence of prop roots with well developed lines for support and

pneumatophores and viviparous germination of seeds. Mangrove forests one

distinguished into the following four types with over tapping constituent species

(Shukla and Chandel, 1972)

1. Tree mangrove forest

2. Law mangrove forest

3. Salt water forest

4. Brakish water forest

I. Tree mangrove forest :- These forests occur on both east and west sea coasts

of India. The best development occurs in Sundarbans. The forest floor is

flooded with salt water daily. Plants may attain a height 10-15 m. and form

an almost closed evergreen forests. The common trees of these forests are

Rhizophora mucronata, Rhizophora conjugata, Avicennia alba, Brugaiera

conjugata, Brugaiera parviflora etc.

II. Low mangrove forests : - These forests grow on salt tidal mud near estuaries,

which is flooded by salt water. Forest is dense but the trees with leathery

leaves attain maximum height of 3-6m. The vegetation consists of a few

species which show gregarious growth habit. Important tree species are

Ceriops decandra, Avicennia alba, Aegialitis rotandifolia etc.

III. Salt water mangrove fores t:- These forests occur beyond tree mangrove

forest in big river deltas where the ground is flooded with tidal water. Silt

deposition and salt content in soil are low. Tree height is up to 2m but girth is

not large. Forests are dense. Pneumatophores are common. The common

plants are Heriticera minor, Excoecaria agallocha, Ceriops decanura etc.

IV. Brakish water mangrove forest :- They grow near the river deltas where

forest floor is flooded with water at least for sometimes daily. Water is

brakish but during rains it is nearly fresh, tree height may reach around 30m.

Forest is dense common species of the forest are Heriteria minor, Xylocarpus

molluccensis, Avicennia officinalis, Sonneratia caseolaris , Sonneratia acida

etc.

The ecological conditions which are essential for the development of

mangrove vegetation.

I. Shallow water with thick mud.

II. Water logged saline soil or sandy or loose soil or heavy clay containing

large amount of organic matter.

III. High rainfall.

IV. High humidity in the atmosphere and cloudy weather.

GENERAL CHARACTERS OF MANGROVE

Habit: -

A great majority of halophytes in the tropical and subtropical regions are shrubs,

but a few of them are herbaceous, for example, Acanthus ilicifolius. In temperate

zones, halophytic vegetation is purely herbaceous. The shrubs are generally dom

shaped in appearance because of their Cymose branching.

EXTERNAL MORPHOLOGY

Stem: -

Stem in several halophytes develops succulence. Salicornia herbacia and Suaeda

maritime may be quoted as familiar examples for it. According to Arnold,

succulents depends on the ratio of absorbed to free ions in the plant cells rather

than absolute amount of Sodium chloride or Sulphate is present. Succulence is

induced only after the accumulation of free ions in an organ increase above a

critical level. Salinity inhibits the cell division and stimulates cell elongation. Such

effects cause decrease in the cell number and increase in cell size, so typical of

succulence is directly correlated with salt tolerance of plants and the degree of

their development can serve as an indicator of the ability of plants to survive in

highly saline habitats. The temperate halophytes are herbaceous, but the tropical

ones are mostly bushy and show dense Cymose branching. Submerged marine

angiosperms are among the very few species of halophytes that do not become

succulent (Shukla and Chandel, 1972).

Leaves: - The leaves in most of the halophytes are thick, entire, succulent,

generally small – sized, and are often glassy in appearance. Some species are

aphyllous. Stems and leaves of coastal aero halophytes show additional mode of

adaptation to their habitats. Their surfaces are densely covered with trichomes.

Leaves of submerged marine halophytes are thin and have very poorly

developed vascular system and frequently green epidermis. They are adapted to

absorb water and nutrients from the medium directly.

Fruits, Seeds and their germination:-

The fruits and seeds are generally light in weight. Fruit walls have a

number of air chambers and the fruits, seeds and seedlings, which can float on

the water surface for pretty long time, are dispersed to distant places by water

current. Mangrove vegetations of tropical seashores from Australia to East Africa

include approximately the same species of plants. Similarly, the mangrove of

West Asia show considerable resemblances with those of East Asia and East

Africa. It is due in part, to the fact that medium and temperature remain uniform

throughout and partially due to the efficient means of dispersal or migration of

plants.

Viviparous mode of seed germination:-

Halophytes or mangrove plants growing in the tidal marshes are met with the

phenomenon of vivipary. Which is defined as the germination of seeds while the

fruits are still attached to mother plants.

Anatomical Features

The appearance and structures which characterize contain groups of plants

sum up to a great extent their ecological and physiological means of adaptation.

Halophytes are no exception to this rule because of specific and typical structural

characteristics, which make them distinguishable, form other groups of plants.

These are. (Pandey, 1981)

1. Large cells and small intercellular spaces.

2. High elasticity of the cell walls.

3. Extensive development of water storing tissues.

4. Smaller relative surface area.

5. Small and fewer stomata.

6. Low chlorophyll contest.

Anatomy of Halophytes Reveals a Number of Xerophytic Feature in Them. These

are follows:-

I. Presence of thick cuticle on the aerial parts of the plant body. The epidermis

of xerosucculents and coastal halophytes is characterized by a cover of waxy

layers in addition to thick cuticle.

II. Leaves may be dorsiventral or Isobilateral. They develop protected stomata

which are not deeply sunken. Epidermal cells are thin walled. The palisade

consists of several layers of narrow cells with intercalated tannin and oil cells.

III. Stems in the succulent plants posses thin – walled water storing parenchyma

cells in them. Mucilage cells may be found in abundance. Epidermal cells of

various mangrove species contain large quantities of tannins and oil droplets.

Cortex is fleshy, several cells thick and old stems it may become lacunar.

Salinity causes extensive lignifications of stele.

IV. The leaves and stems of coastal halophytes are abundantly covered with

various types of simple and branched trichomes giving the plants a grayish

appearance. The trichomes may play a positive role.

a. Reducing water economy.

b. Reducing the temperature of their leaves and

c. Preventing seawater droplets from reaching the live tissue of leaves.

V. Leaves of many species of mangrove are dotted with local cork formation

‘cork warts’ salt secreting glands and aqueous tissue may be found in some

halophytes (Shukla & Chandel, 1978).

Objectives of the present study

To study the morphological characters of Avicennia officinalis L.

To study the anatomical characters of the leaf and stem.

To identify the peculiar morphological & anatomical characters present in

Avicennia officinalis L.

Chapter: 2

Materials & Methods

Specimen for the present study was collected from Kumbalanghi. It is an

Island. This small naturally beautiful Island has pockets of mangrove vegetation

(Fig: ). Rich growth of mangrove was observed in certain regions. Plant specimens

were collected & photographs were taken for the identification. Section of stem,

leaf & petiole were taken for the anatomical study. Photographs were taken.

Immediately after collection, the plant materials were put in a plastic bag.

The specimens were cut into pieces of convenient size & preserved in F.A.A. the

date and time of collection, Name of the plant family, plant size, flower character,

ecological conditions, Morphological characters & Anatomical characters were

noted.

The sections taken from the plant were washed well. The sections were

stained in aqueous safranin and mounted in glycerin. The preparations were

observed under the compound microscope.

From a proper section of a plant all the peculiarities were noticed. Along

with place, date, binomial of concerned plant, Family, growth & Anatomical

features were recorded. A comparison was made between the two species

regarding the histology of the primary and secondary anatomical structures. Then

the similarities and contrast between the two plants were noted.

Chapter: 3

Observation & Discussion

Avicenna Officinalis L.

Common Name : White mangrove

Local Name : Uppatha

Family : Verbenaceae / Avicenniaceae

Avicenniaceae is the important mangrove family in India. Under this family

there is only one genus, ‘Avicennia L.’ along with its 3 species & one variety

common in India.

1. Avicennia officinalis L.

2. Avicennia alba Blume.

3. Avicennia marina Var.

Distribution: - It is distributed throughout the tropical & subtropical region. Very

common in the inter tidal zones.

Habit: - Evergreen, Medium to tall tree attain the height between 15m – 20 m.

[Plate 1; Fig: 2]

External Morphology

Stem: - Bark smooth, whitish, much branched, deliquescent, irregularly spreading

branches; gregariously grow in the intertidal forest.

Roots: -

Conspicuous, negatively geotropic aerial roots – pneumatophores or breathing

roots are present. They are numerous, erect pencil like, without any secondary

growth, attain the height unto 0.30 cm pneumatophore develop in the inter–tidal

flat ground; developed from the surface spreading underground horizontal roots.

Frequently branches of stilts roots developed from the trunk base in stressed

condition and when the tree bents on one side.

Leaves: -

Simple, opposite decussate, exstipulate, cauline, petiolate, petiole 1.5cm long.

Green glaberous, pulvinous, lamina elliptic obovate, broadly ovate / obovate,

entire, round apex, slightly fleshy, dorsiventral, dorsal side dark green, shining,

unicostate venation, leaf turing black on drying. Leaves contain salt secreting

glands.

[Plate 2; Fig 2]

Inflo rescence :-

Cyme compound spikes, peduncle unto 25cm long [Plate 1; Fig: 3]

Flower: - Flower buds glabrous, round brown, flowers zygomorphic, complete,

bisexual, regular, cyclic, rosaceous, sessile, dull yellow, 0.8cm x 1.5 cm across,

slightly foetied with 10-12 flower in each branch.

Calyx: - Sepals are 5, polysepalous

Corolla: - Petals are 4, gamopetalous

Androecium: - Stamens 4, epipetalous, filament 0.20 cm long

Gynoecium:- Ovary superior, 0.7cm long.

Fruit: - Capsule fleshy, ovoid, opaque, green, densely hairy 3cm long & 2.8 cm

broad, flattened with a short apical beak. [Plate 1; Fig:4]

Seed: - Simple, dark green, completely occupy the fruit cavity

Pneumatophore:- Avicennia have pencil like upto 30cm high slender negatively

geotropic air breathing roots, the pneumatophores occasionally form slender stilt

roots from the trunk bases. Pneumatophores of these members of Avicennia L.

have no secondary growth; small pores are scatteredly present on the surface of

these aerial roots for performing effective root zone respiration in this compact

inter-tidal saline soil. Sometimes the fibrous 0.5 cm – 1 cm diameter [Plate 1; Fig:

5,6].

Seed Germination: - Seeds of the Avicennia sp. germinate soon after their fruits

fall from the mother plant. In this case, their fruits mature in the mother plant

itself and develop the seeds to their optimum condition for effective germination.

This phenomenon is known as pseudoviviparous or incipient viviparous seed

germination. (Naskar, 2002).

Anatomical Features

Leaves : -

Leaves may be dorsiventral. Thin walled epidermal cells are present in the upper

epidermis, and it is covered by cuticle. They develop protected stomata, which are

not deeply sunken. Epidermal cell contain oil drops and Tannin cells. Palisade

tissue is present it contain mucilage cells. Below the palisade tissue spongy tissue

is present. Lower epidermis is single layered and it is covered by cuticle. The

leaves covered with various types of simple and branched trichomes. It gives the

grayish appearance and it has protective function. Salt secreting glands are also

present in the leaves. The glands have one or two basal collecting cells. One or two

stalk cells and a number of radially arranged secretary cells, which are covered

with a thin cuticle layer. [Plate 2; Fig: 2]

Stem :-

Single layer of epidermis and it is covered by thick cuticle. Below the epidermis

one or two layers for Hypodermis is present. The outer cortexes contain tannin

cells. Cortex contain thick walled cells. Inner cortex contain sclerids endodermis is

single layered. Pericycle is multilayered. Below the pericycle, vascular bundles are

present. Xylem conjoint and collateral. Vascular bundle with endarch xylem.

Tannin cells and oil drops are also present in the inner pith. Trichomes are

present. The branched trichomes giving the plants a greyish appearance. The

trichomes may exert, affecting water economy, affecting the temperature of their

leaves and preventing sea water droplets from reaching the live tissue of leaves.

[Plate 2; Fig: 4, 5, 6]

Petiole:-

The epidermis of the petiole resembles that of the corresponding surface of the

lamina except that there are no glands or stomata on the underside. The

parenchymatous ground tissue contains scattered mechanical cells bearing a

lignified thickening, which is reticulately pitted, the pits being sometimes so large

that the thickening is reduced to a network of narrow strands. Well-developed

lacuna occurs at the sides of the petiole. The vascular system is traced from the

stem. At the node the bundles lying adjacent to the base of the petiole passon

masse into the petiole. A small group of bundles is derived from further round the

stem on either side. The intervening vascular tissue forms the axillary bud traces.

A relatively large bundle group is derived from still further round the stem on

either side. The vascular tissue, with the exception of a small part of each of the

larger subsidiary groups assembles about the central ground tissue of the petiole.

The central ground tissue of the petiole includes numerous small bundles of

phloem, the larger of which have a small quantity of xylem associated with them.

These are embedded in rows shortly elongated parenchyma. Phloem consists of

numerous small sieve tubes and companion cells. Cambium is fascicular only. The

depression at the base of the petiole is fringed with simple filamentous hairs

composed of three or four cells lined with shorter hairs of the same type

intermingled with glandular hairs much larger than those in the lamina. The stalk

and foot of each gland is unicellular. [Plate 2; Fig 7,8]

The anatomical observations showed four common features in mangrove plants.

I. Colorless water storage tissue.

II. Short terminal trenches at vain endings.

III. Absence of sclerotic bundle sheath.

IV. Sclerids of various shapes.

Considerably thick cuticles are present on the epidermal layers of

mangrove taxa, which also restricts non stomatal water loss. Due to the presence

of colourless water storage tissue at different levels of mesophyll and hypodermal

layers, many leaves become thick and succulent, which can be correlated with the

extra water storage capacity (Vasishta, 1978)

Comparison of Morphological Characters

Avicennia officinalis General Features

1 Colour of plant White in colour Green in colour

2 Stilt root The stilt root is poorly developed

The stilt root may be strong and extensively developed.

3 Pneumatophore Present Present

4 Fruit Flattened with apical beak up to 3cm long and 2.8cm width

Apical beak is absent in most species

5 Germination Crypto-viviparous seedling germination

Viviparous germination

Comparison of leaf anatomy

General Features Avicennia officinalis

1. Cuticle is very well developed Cuticle is thick

2. Epidermal cells are heavily thickened Epidermal cells are thickened

3.Stomata, confined only to lower surface and sunken

Stomata are present in the lower epidermis.

4. Mesophyll is well differentiated into palisade and spongy tissue

Palisade tissue is seen beneath the water storage region. Then comes spongy tissue

5. Salt gland may be present. Salt gland present on upper epidermis, which excrete excess salt.

Comparison of stem anatomy

General Features Avicennia officinalis

1. Cuticle is thick Cuticle is thick

2. Epidermal cells are heavily thickened Epidermal cells are thickened

3.Primary cortex is lacunar, filled with tannin, and oil

Cortex is collenchymatous

4. Pericycle is several layered, sclerenchymatous.

Pericycle is a composite and continuous ring.

Two types of leaf hairs occur in some species glandular (salt secreting

glands) and non-glandular. The glandular hairs are present on both the abaxial

and adaxial surface in Acanthus illicifolius and Avicennia, but are totally absent in

the rest of the species. The non-glandular hairs develop only on the abxial surface

in Avicennia species and Acanthus. The present study confirms the above

observation (Vasishta, 1978).

The glandular hairs have one or basal collecting cells. One or two stalk cells

and a number of radially arranged secretory cell, which are covered with a thin

cuticle layer. Non-glandular hairs have a multicellular sclerotic body. Which

distally produce a shield, like expanse of thin walled cells or branched star-like

cells in Heritiera or unbanched filamentous body in Avicennia (Vasishta, 1978).

Guard cell has cuticular beak like outgrowth (ledges) on either the outer

side of both outer and inner side of the stomatal pore in Acanthus and

Rhizophora. Stomata are usually restricted to the abaxial surface of dorsiventral

leaves and are scattered throughout the lamina. The hypodermis is composed of

one or more layers of colourless cells below the adaxial epidermis. These

colourless cells often function as water storage tissue. Two types of hypodermis

have been distinguished based upon the number of hypodermal layers.

1. Hypodermis is one layered, below the adaxial epidermis cells are polygonal,

cubical or narrow and sometime extensively vertically elongated in Acanthus.

2. Hypodermis is more than two layered, cells are cubical or polygonal in

Transverse section larger than epidermal cells, in Avicennia and Rhyophora.

The mesophyll is composed of thin called chlorenchymatous cells and is well

differentiated in the dorsiventral leaf into one or more layers of adaxial

anticlinally extended palisade cells & oval or round shaped compact or loose

abaxial is diametric cells in Acanthus, Avicennia and Rhizophora (Vasishta,

1978). Similar observations are made in the present study.

SUMMARY

Mangrove plants and the mangrove ecosystem or the mangal in totality are

most important in the perspectives of its economic potentialities, as mangroves

provide ideal habitats for economic species of fish, shrimps, prawns, crabs and

good number of threatened, rare and endemic, but most important species of

aquatic and terrestrial fauna. The plants are typical halophytes which are

characterized by presence of prop roots with welll developed knees for support

and pneumatophores and viviparous germination of seeds.

Avicennia is the important mangrove plant belonging to the family

verbenaceae and it is commonly known as ‘White mangrove’. It is evergreen,

medium to tall tree, attain the height between 15m-20m.

In Avicennia officinalis L. stem is smooth, whitish much branched,

deliquescent, irregularly spreading branches. Leaves are simple, opposite,

exstipulate, petiolate, green glaberous, dorsiventral. Leaves also contain salt

secreting gland. Anatomical features on Avicennia officinalis are, stem contain

single layer of epidermis, multilayered hypodermis. Cortex contains tannin cells

and sclerids. Single layered endodermis and multilayered pericycle. Xylem is

endarch. Trichomes are present. Leaves are dorisventral. Thin walled epidermis

with cuticle. Palisade tissues contain mucilage cells. Below the palisade tissue

spongy tissue are seen. Lower epidermis is single layered and covered by cuticle.

Stomata is present but which are not deeply sunken. Salt secreting glands and

trichomes are also present. Petiole also contain trichomes.

The anatomical observations showed common features in mangrove plants:

1. Colourless water storage tissue

2. Short terminal trachieds at vain endings

3. Absence of sclerotic bundle sheath

4. Presence of various shape sclerids

5. Presence of thick cuticle

6. Presence of tannin cells

7. Stomata are present but which are not deeply sunken

However salt secreting gland present in leaves and stem are the unique

features of the plant. The stomata are also not sunken much. The most

important feature of this plant is absence of true vivipary. The fruits fall down

and germinate there after.

References

Eames A.J (1961) Morphology of angiosperms, New york : Mc Graw Hill.

Naskar.K (2002) Manual of Indian mangroves, Daya publishing House, New Delhi.

Pandey B.P (1981) A Text book of botany Angiosperms, S.chand & company Ltd,

New Delhi.

Shukla R.S and Chandel P.S (1972) Plant ecology, S.chand & company Ltd, New

Delhi.

Vasishta P.C (1978) A text book of plant anatomy, Messrs Pradeep publication.

PLATE 1

Figure 1: Mangrove vegetation in Kumbalangi

Figure 2: Habit- Avicennia officinalis. L

Figure 3: Inflorescence

Figure 4: Pneumatophore habit

Figure 5: Pneumatophore

PLATE 2

T.S of leaves- Avicennia officinalis.L

Figure 1: Hair

Figure 2: Gland

Figure 3: Trichome

Figure 4: T.S of stem Avicennia officinalis.L

Figure 5: T.S of stem Avicennia officinalis.L enlarged

Figure 6: Hair

Figure 7: T.S of petiole Avicennia officinalis.L

Figure 8: Hair