onPLANT PHYSIOLOGY showing morphological symptoms. There is some evi-dence (6, 12) that boron deficiency has an effect on the translocation of sugars, and possibly other organic compounds,

HELSON AND 'MINSHALL-PETROLEUM OILS ON RESPIRATION1

The sharp rise immediately following the applica-tion of these oils was shown to be a true respirationincrease and was due neither to the evolution of avolatile substance with an infrared absorption bandnor to the expulsion of CO2-rich air by the entry ofoil into the intercellular spaces.

IUnder anaerobic conditions, the non-herbicidal,white, paraffinic oil had no effect on the respiration ofparsnip leaves while the petroleum naphtha caused anincrease, indicating that the paraffinic oil stimulatedthe aerobic oxidation processes while the petroleumnaphtha stimulated both the aerobic oxidation proc-esses and the glycoly-tic processes of respiration.

The authors wish to express their appreciation toMr. R. E. Emond of Imperial Oil Limited for pre-paring the naphthene and the naphthene-paraffin frac-tions of petroleum naphtha; to the Shell Oil Coin-pany of Canada Limited, for the chemical analysis ofpetroleum naphtha; to Dr. R. C. Turner for surfacetensions, Dr. D. AM. Ailler for viscosities and 'Mr.R. A. Latimer for acid and peroxide contents of petro-leum naphtha and the paraffinic oil. Technical assist-ance by Mr. A. G. Moulds and AMr. G. R. Dupuis isgratefully acknowledged.

LITERATURE CITED1. AUDUS, L. J. Mechanical stimulation and respira-

tion of the green leaf. III. The effect of stimula-tion on the rate of fermentation. New Phyto!ogist39: 65-74. 1940.

2. GREEN, J. R. Effect of petroleum oils on the Irespi-ration of bean plants, apple twigs and leaves, andbarley seedlings. Plant Physiol. 11: 101-113. 1936.

3. HELSON, V. A. and MINSHALL, W. H. The effects ofherbicidal oils on the photosynthesis, respiration

and transpiration of parsnip and mustard. Ab-stracts, Amer. Soc. Plant Physiol. Pp. 9-10. 25thAnnual Meeting, Columbus, Ohio. 1950; P. 21.27th Annual Meeting, Ithaca, New York. 1952.(Mimeographed.)

4. JOHNSON, C. M. and HoSKINS, W. M. The relationof acids and peroxides in spray oils to the respira-tion of sprayed bean leaves and the developmentof injury. Plant Physiol. 27: 507-525. 1952.

5. KELLEY, 1V. XV'. Effect of certain hydrocarbon oils onthe respiration of foliage and dormant twigs of thethe apple. Agr. Expt. Sta., Illinois, Bull. 348: 369-406. 1930.

6. KNIGHT, H., CHAMBERLIN, J. C., and SAMUELS, C. D.On some limiting factors in the use of saturatedpetroleum oils as insecticides. Plant Physiol. 4:299-321. 1929.

7. MINSHALL, W. H. and HELSON, V. A. The herbi-cidal action of oil!s. Proe. Amer. Soc. Hort. Sci.53: 294-298. 1949.

8. OBERLE, G. D.. PEARCE, G. W., CHAPMAN. P. J., andAVENS, A. W. Some physiological responses ofdeciduous fruit trees to petroleum oil sprays.Proc. Amer. Soc. Hort. Sci. 45: 119-130. 1944.

9. RALSTON, A. WX., CHRISTEN-SEN, C. W., and JOSH, G.Use of mercurated fatty compounds as weed killers.Oil & Soap 14: 5-7. 1937.

10. SCARTH, G. W., LOEwY, A., and SHAW, M. Use ofthe infrared absorption method for estimating thetime course of photosynthesis and transpiration.Canadian Jour. Research C, 26: 94-107. 1948.

11. WXEDDING, R. T., RIEHL, L. A., and RHOADS, W. A.Effect of petroleum oil spray on photosynthesisand respiration in citrus leaves. Plant Physiol.27: 269-278. 1952.

12. YOUNG, P. A. and MORRIS, H. E. Injury to apple bypetroleum oil sprays. Jour. Agr. Research 47:505-522. 1933.

THE ROLE OF BORON IN THE TRANSLOCATION OF ORGANICCOMPOUNDS IN PLANTS12

EDWARD C. SISLER, W. M. DUGGER. JR.3 A-ND HUGH G. GAUCHDEPARTMENT OF BOTANY, NORTH CAROLINA STATE COLLEGE, RALEIGH, NORTH CAROLINA;

DEPARTMENT OF HORTICULTURE, UNIVERSITY OF FLORIDA, GAINESVILLE. FLORIDA;AND DEPARTMENT OF BOTANY, UNIVERSITY OF MARYLAND,

COLLEGE PARK, MARYLAND

The essentiality of boron for higher plants wasdemonstrated in 1910 (1). Since then several thou-sand reports have appeared and numerous physiologi-cal roles have been ascribed to boron. The literaturehas been reviewed by Gauch and Dugger (7) and in-terpreted in the light of some of the more recent evi-dence. They (6) recently postulated that boron may

1 Received July 14, 1955.2 Contribution No. 2634, Maryland Agricultural Ex-

periment Station, Department of Botany. This researchwas supported in part by a contract with the AtomicEnergy Commission, No. AT(30-1)-1504.

3 Formerly of Department of Botany, University ofMaryland, College Park, Maryland.

be necessary in order for sugar to move through theprotoplasmic membranes. According to their theory,boron mav react with the sugar molecule to form acomplex which then moves through the membranewith greater facility than the sugar molecule itself.They also recognized that boron might instead beassociated with the membrane, reacting with the sugarmolecule at this locus. They believed that the evi-dence favors this latter mechanism.

MJany authors have concludced that the high con-centration of sugars in the leaves of boron-deficientplants was due to a breakdown of the conductive tis-sues with a concomitant reduction in translocation.-Most of these studies have beein conduieted on plants

11

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PLANT PHYSIOLOGY

showing morphological symptoms. There is some evi-dence (6, 12) that boron deficiency has an effect onthe translocation of sugars, and possibly other organiccompounds, before vascular derangement occurs.

In this study, an attempt was made to comparethe translocation of carbohydrates in plants grown ina boron-sufficient nutrient solution with that of plantsgrown in a boron-deficient nutrient solution and tocorrelate this information with the observed symp-toms of boron deficiency. Experiments were con-ducted on plants soon after the boron supply wasremoved, as well as on those showing symptoms of thedeficiency.

1\IATERIALS AND METHODSCULTURE METHODS: Marglobe tomato (Lycoper-

sicum esculentum Eill.) plants were used in all of theexperiments. It has been shown that the boron re-quirement for tomato is not altered by photoperiod(15). Lights were used, however, during the wintermonths to augment photosynthesis and thus to im-prove plant growth.

Seedlings were produced in flats containingf sand.At the desired stage of growth, they were trans-planted to automatically-irrigated sand culture equip-ment similar to that described by Gauch and Wad-leigh (8). Five, 4, and 2 ml of molar solutions ofCa(N03)2-4 H.,O, KH2PO4, and MgSO4 7 H20, re-spectively, were added per liter of de-ionized water.Using monosodium, iron, ethylene-diaminotetraacetate(5000 ppm Fe) and a "supplementary solution" (50ppm Zn as ZnSO4 7 H20, 16 ppm Cu as CUSO4 5H20, andI 500 ppm Mn as MnCl2) 0.6 ml and 1 ml,respectively, of each of these two stock solutions wereadded to each liter of the nutrient solution. Boron,as H3BO3, was either absent or present in varied con-centrations.

For the early growth of plants, 0.05 ppm of addedboron appeared to approach sufficiency but, to ensurean adlequiacy, 0.1 ppm of boron was generally em-ploy-edl. Unless otherwise indicated, plants weregrown to the desired stage with 0.1 ppm of boron. Atthis time the solutions were replaced with de-ionizedwater for 12 hours to free the cultures of boron. Fol-lowing this treatment, the nutrient solutions were re-plenished, omitting boron in those solutions whichwere to be deficient. Usually solutions were changedweekly (luring the course of a given experiment.

Using the carmine method (9), attempts weremade to determine the amount of boron in the de-ionized water but, even after concentrating 100-fold,none could be detected. Since a progressive increasein growth throughout the following portion of therange of boron concentrations, 0, 0.002, 0.005, 0.0075,0.01, 0.015, and 0.02 ppm was observed, it wtould ap-pear that the boron content of the de-ionized watermust have been very low.

EXPERIMENTS WVITH C14-LABELED SUCROSE: Ex-periments on the absorption and translocation of sugarin tomato plants were performed in the greenhouse.The third leaf from the tip of each plant was ex-

cised so as to leave intact as much of the petiole aspossible. The tip of the petiole at this node was thenimmersed in 3 ml of a 7 % solution of uniformly-labeled sucrose having a specific activity of 0.0343,uc per ml. After the desired length of time, theplants were fractioned and dried in a hot-air, forcecl-draft oven at 700 C prior to grinding and the prepara-tion of samples for counting.

EXPERIMENTS WITH C1402: Experiments involv-ing CO2 were performed in an atmosphere containing0.5 % CO2 so that the system would not be depletedof CO, during the course of the experiments. Thetotal amount of C14 in the closed system was variedlbetween 20 and 40 microcuries. The C14 was ob-tained as BaCO3 and was converted to NaCO3 inwater to facilitate precision in the measurement ofaliquots. Boron-deficient and sufficient plants werecarefully potted from sand culture, watered, andplaced in the dark for 24 hours to lower the internalcarbohydrate level. One intact leaf of each plant wascarefully placed in a desiccator (exposure chamber),with modeling clay being inserted in the notch in thelid to make a seal around the petiole.

After a predetermined amount of evacuation,C1402 was released in a separate chamber (desicca-tor) with H3PO4 and circulated with a model T-4Sigmamotor rubber-tubing pump for 10 minutes toallow the system to equilibrate. Light (approxi-mately 250 fc) was supplied by two 200-watt incan-descent light bulbs and a fluorescent light in the topof the hood. Lights were adjusted with the aid of alight meter so that the illumination would be as uni-form as possible. The CO, was circulated within theclosed system during the course of the experiment.Under these circumstances, preliminary experimentsindicated that the temperature in the chamber didlnot rise more than 2° C above room temperature.After the desired length of time, plants were pressedand (Iried for radioautographs or fractioned and driedin an oven at 700 C.

Samples for raclioassay were prepared on ringscovered with celluloid tape, as described by 'Mitchelland Linder (13), and counted with a windowless flowcounter. The weight of the samples was generallyabout 15 mg. Radioautographs wAere prepared in theusuial manner with Kodak x-ray film. Exposure timewas 2 days.

CHROMATOGRAPHiC TECHN-IQUES: After killing illboiling ethanol, the leaves were extracted in a Soxhlet,and the soluble materials were concentrated on asteam bath.

Organic acids were separated (3) with n-butylalcohol, acetic acid, and water (4 :1:1, v/v) and (5)ether, acetic acid, and water (13: 3:1, v/v). Aminoacids and sugars were separated with n-butyl alcohol,acetic acid, and water (4:1: 1, v//v) and phenol andlwater (3: 1, v/v). The indicators were bromeresolgreen for organic acids, ninhydrin for amino acids,naphthoresorcinol for sucrose, and benzidine for glu-cose and fructose. The general methods, outlined by

12



SISLER ET AL-BORON IN TRANSLOCATION

Block et al (3) for indicators andI solvents, were em-

ployed.

RESULTS AN-D DISCUSSIONMORPHOLOGICAL SY'MPTOMS: Johnston and Dore

(10) and Johnston and Fisher (11) have describedboron-deficiency symptoms on tomato. There are nu-

merous other reports of boron-deficiency symptomsin general. 'Many of the symptoms of boron-defi-ciency indicate a possible deficiency of carbohydrates.The fact that root tips die first (4) is indicative sincethey are close to the boron which is available but are

far from the carbohydrate supply. During the seed-ling stage, the cotyledons of boron-deficient plants,grown in sand culture, enlarged to approximatelytwice the size of those of normal plants. This mightindicate that boron-deficient plants are capable of ex-

panding tissues near a source of supply of carbohy-drate, but that they are not capable of developingnew leaves to which large amounts of carbohydratesmust be translocated. Young boron-deficient tomatoplants, which have several sets of leaves, develop axil-lary shoots after the tips die (10). This again maybe a response to an inadequacy of the mechanism fortranslocation. It is evident that an imbalance of hor-mone, associated with the death of the tip, could alsobe involved.

APPLIED SUGARS: Several authors have impliedthat boron may be directly involved in the transloca-tion of sugars (6, 12, 14). Inasmuch as stem-tips are

among the first parts to die, attempts were made toprev-ent this occurrence by an application of aqueousuglar solutions to the tips. Solutions containing 4 %

gltucose, fructose, or sucrose were sprayed on the tipsof plants that were receiving a boron-deficient solu-tion. There was no apparent improvement of the"boron-deficient" plants receiving these applicationsof sugar. These results may have been caused by a

failure of the applied sugars to penetrate even theotuter layer of cells when the plants were boron de-ficient.

By immersing the tips of the petiole at the thirdnode (leaf blade excised) in a 7 % C14-labeled su-

crose solution, the plants absorbed the sucrose andtranslocated it (or its hydrolytic products), so that a

detectable amount was in the tips within two hours.Translocation was primarily to the tip and the firstleaf below the tip, although the second leaf below was

sometimes as active as the first leaf. Other leaves(lid not have a detectable amount of radioactivity inthem. As shown in table I, plants grown in the ab-sence of boron, but not yet showing visible symptomsof boron deficiency, translocated more sucrose (or itshydrolytic products) when 50 ppm of boron were

added to the solution than when sucrose alone was

applied. Normal plants, grown with 0.5 ppm boron,did not show a consistent increase in translocationwhen boron was added to the sugar solution.

When plants were showing morphological boron-deficiency symptoms, the uptake and translocation ofapplied sucrose to all parts of the plant were reduced

TABLE IEFFECT OF BORON ON THE DISTRIBUTION OF RADIOACTIVITYIN NORMAL AND BORON-DEFICIENT TOMATO PLANTS. C -LABELED SUCROSE WAS INTRODUCED AS A SOLUTION THROUGHTHE STUMP OF THE PETIOLE AT THE THIRD NODE FROMTHE TIP. (EACH VALUE FROM A SAMPLE COMPOSED OF

DUPLICATE PLANTS)

CPM/10 MGS OF DRY PLANT MATERIAL

NORMAL PLANT DEFICIENT PLANT

PLANT PART SUCROSE SUCROSESUCROSE AND SUCROSE ANDAPPLIED BORON APPLIED BORON

APPLIED APPLIED

2-hour samplingTip ........... 18 10 9 30First leaf 13 22 8 52Second leaf 7 4 4 26Average 13 12 7 36

.3-hour samplingTip.18 27 23 35First leaf 19 43 30 79Second leaf 6 28 53 23Average 14 33 35 46

5-hour sanplingTip.52 28 35 72First leaf 74 31 58 128Second leaf 16 28 15 33Average 47 29 36 78

7-hour samplingTip.60 164 70 87First leaf 104 120 89 145Second leaf 31 50 64 109Average 68 111 74 114

(table II). The addition of boron at this stage ap-parently did not facilitate the translocation of sugar.Boron appears to aid in the translocation of carbo-hydrates before morphological symptoms are visible,but it does not increase the amount of translocation

TABLE IIEFFECT OF BORON ON THE DISTRIBUTION OF RADIOACTIVITYIN NORMAL AND IN PLANTS SHOWING BORON DEFICIENCYSYMPTOMS. C'4-LABELED SUCROSE WAS INTRODUCED AS ASOLUTIONT THROUGH THE STUMP OF THE PETIOLE AT THETHIRD NODE FROM THE TIP. (EACH VALUE FROM A SAM-

PLE COMPOSED OF DUPLICATE PLANTS)

CPM/10 MGS OF DRY PLANT MATERIAL

NORMAL PLANT DEFICIENT PLANTPLANT PART SUCROSE SUCROSE

SUCROSE AND SUCROSE ANDAPPLIED BORON APPLIED BORON

APPLIED APPLIED

Tip ........... 100 100 18 35Upper leaves 66 97 30 17Lower leaves 36 38 10 1Stem.64 55 16 30Roots.49 51 14 15Average ...... 65 68 18 20

13



PLANT PHYSIOLOGY

regions of the plant usually associated with borondeficiency symptoms received the major portion ofthe photosynthate. This was true even when symp-toms were severe (fig 2). The relative amounts ofthe photosynthate translocated to each region can bebetter evaluated from the counting data (table III).

The counting data showed that a greater per-centage of the fixed C14 was translocated by boron-sufficient plants than by boron-deficient plants. Thiswas more evident in the basal than in the apical por-tion. The magnitude of this difference could easilvaccount for the death of plant parts or organs withinherently rapid rates of respiration. This would beespecially true of the roots since they are farthestfrom the source of production of carbohydrates. Itis possible that other essential compounds, w hichmust be translocated from one part of the plant toanother, would not be as readily translocated. Alex-ander (2) and Chandler (4) reported that boron-deficient plants lose their capacity to respond togravity. This would indicate that there is some rela-tion between boron and the production, translocation,or action of hormones. NMitchell et al (12) found that

FIG. 1 Radioautogiraph illuistrating the distributionof C'4 in boron-sufficient plants aftei 4 hrs of photosyn-thesis. (Arrow indicates position of exposed leaf. Rootsaxe light area at left, bottom.)

after symptoms are visible. The results of this ex-periment suggest that perhaps injury to the phloemhad occurred which applied boron could not alleviate-at least during the course of these experiments.

C1402 EXPERIMENTS WITH PLANTS SHOWINGBORON-DEFICIENCY SYMPTOMS: Plants xw ere subjectedto C1402 to determine whether the normal distribu-tion pattern of the photosynthetic products would bealtered when plants were boron deficient. Leaves ofnormal tomato plants and those of plants showingsevere svmptoms of boron deficiency were placed ina specially-designed chamber and exposed to 20 mi-crocuries of C1402 for 4 hours.

Radioautographs of these plants indicated thatmost of the photosynthetic products were translo-cated into the tip, first leaf below the tip, and theroots of normal plants (fig 1). Only traces of radio-activity were found in the other leaves. When plantswx'ere showing severe symptoms of boron deficiency,most of the translocation of the photosynthetic prod-ucts was also to these same parts. The veinal pat- FIG. 2. Radioautograph illustrating the distributiontern in normal plants was somewhat more distinct of C"4 in boron-deficient plants after 4 hrs of photosyn-than that in boron-deficient plants. Those areas or tlhesis. (Arrow indicates position of exposed leaf.)

14




TABLE IIIDISTRIBUTION OF THE PHOTOSY-NTHETIC PRODUCTS OF BORON-DEFICiENT AND BORON-SUFFICIE.NT

PLANTS AFTER 4 HRS OF PHOTOSYNTHESIS IN AN ATMOSPHERE CONTAINING C402.(EACH VALUE FROM A SAMPLE COMPOSED OF DUPLICATE PLANTS)

C14 AS %lc OF TOTAL AMOUNT FIXED PER PLANT

ExPT I EXPT II ExPT IIIPLANT PART 9/18/54 9/21/54 9/24/54

BORON SUFFI- BORON DEFI- BORON SUFFI- BORON DEFI- BORON SUFFI- BORON DEFI-CIENT PLANT CIENT PLANT CIENT PLANT CIENT PLANT CIENT PLANT CIENT PLANT

Tip ..................... 1.9 1.7 0.7 2.1 0.2 0.3First leaf .......... ... 0.7 0.2Stem above treated leaf 5.2 2.2 8.3 6.2 11.0 7.5Stem below treated leaf 4.3 6.5 19.7 32 7.0 1.6Other leaves.0.3 0.5 1.8 7.5 0.7 0.1Roots.5.9 1.6 1.3 0.8 0.2 0.4Total.17.6 12.5 31.8 19.9 19.8 10.1

2,4-D and other growth-modifying substances weremore rapidly translocated when boron and sugarswere also applied. A decrease in the translocation ofvarious compounds could be involved in the appear-ance of boron-deficiency symptoms but, as with hor-mones, the effect of boron on the translocation of car-bohvdrates may be the main effect.

C140, EXPERIMENTS WITH PLANTS NOT SHOWINGBORON-DEFICIENCY SYMPTOMS: In order to determinehow the rate of translocation was altered over shortintervals of time when boron was absent from thenutrient solution and to determine at what stage ofboron deficiency a difference in translocation could benoted, a series of plants was exposed to 20 uc ofC1'4O for 20 minutes. At the completion of the ex-posure period the plants were fractioned, dried, andprepared for radioactivity assay. The plants weregrown to about 10 inches in height with 0.1 ppm ofboron, and then half of them were placed on a boron-free nutrient solution. The others were continuedwith 0.1 ppm of boron. Boron-deficient plantsshowed the characteristic symptom of brittleness atthe end of 8 davs and were just beginning to showother morphological symptoms at the end of 14 dayswhen the experiments were discontinued.

Plants exposed to 20 lic of C14 for 20 minutes hada measurable amount of radioactivity in the first 4

TABLE IVPERCENT OF TOTAL PHOTOSYNTHATE TRANSLOCATED AFTER20 MINT OF PHOTOSYNTHESIS WITH 20 MICROCURIES OFC 402. (EACH VALUE FROM A SAMPLE COMPOSED OF DUPLI-

CATE PLANTS)

DAYS ON NO BORONI 0.1 PPM OF % INCREASETREATMENT ADDED BORON ADDED DUE TO BORON

2 0.32 0.29 -124 0.42 0.78 816 0.55 1.63 2148 0.17 0.16 - 610 0.08 0.15 8814 0.05 0.07 40

cm up and down the stem from the point of attach-ment of the C14-exposed leaf. After 4 days, plantslacking boron showed a decrease in the amount offixed carbon that was translocated, as compared tonormal plants treated in the same manner (table IV).With the exception of the eighth day, this decreasewas observed throughout the experiment. On thisday one of the duplicate boron-deficient plants waslost.

Since 20 /Ac of C1402 did not result in a detectableamount of radioactivity beyond 4 cm up and downthe stem, the experiment was repeated with 40 ,uc ofC1402, and 30 minutes (20 min of light; 10 min dark)were allowed for translocation. It was then possibleto measure activity in the first 8 cm up and downthe stem.

Vernon and Arnoff (16) found that the radioactiv-ity in soybean plants treated with C1402 for 20 min-utes decreased logarithmically with the distance fromthe point of attachment of the treated leaf. This wasalso found to be the case in these experiments with

6-8

U.

< 4-6J

InwU)00.x 2-4w

a 0-2

0\ 0

A * + BORON DOWNA ' - BORON DOWN0 ' + BORON UP*' -BORON UP

1 2 3 4LOG C/M/PART

FIG. 3. Logarithmic plot of C'4-radioactivity in 2-cmstem segments of boron-deficient and boron-sufficienttomato plants treated with 40 ,uc of C1402. In light,20 min; darkness, 10 min.

15



PLANT PHYSIOLOGY

tomato plants. Samples were counted in 2-cm seg-ments to include a distance of 8 cm up and down thestem from the locus of the treated leaf. The activitywas not sufficiently high in the sections of the stembeyond 8 cm to be determined accurately. The earlystages of boron deficienev did not alter this logarith-mic pattern of distribution. Movement in bothboron-deficient and sufficient plants was usuallygreater in a downward than in an upward direction inthe stem. A typical logarithmic plot of the activityfound in these segments is shown in figure 3.

The total amount of C14 fixed by boron-deficientplants did not vary much from that of controls. Thevariation in the per cent of translocation from oneinterval to the next was largely due to unknown fac-tors. It must be borne in mind, however, that treat-ment started at a stage of vigorous growth and thatplants treated on the fourteenth day were about twiceas large as those treated on the second day. The leafselected for exposure on any given day was that leafnearest the middle of the plant. As the plants de-veloped, this resulted in a shift in the stage of de-velopment of the exposed leaf. Care was taken inselecting plants so that the boron-deficient and suffi-cient plants would have morphologically equivalentleaves on any given day.

In all cases boron-sufficient plants translocated agreater percentage of the C14 fixed, on any given day,than did comparable boron-deficient plants (table V).The amount of translocation in boron-deficient plantsdropped to a low level after only 2 days and re-mained lower than that of boron-sufficient plants dur-ing the course of the experiment.

CHROMATOGRAMS OF SOLUBLE PLANT MATERIAL:Chromatograms made from leaf and stem extractsdid not indicate large differences in organic acids be-tween boron-deficient and sufficient plants. Citric,malic, succinic, and an unknown acid whose Rf corre-sponded to published values for a-ketoglutaric acid,were well resolved. Visual estimation of the amountof each acid indicated relatively little difference.

Chromatograms of amino acids resolved into eightspots. No visual difference was apparent betweenboron-deficient and boron-sufficient stems and leaves.Similarly little difference was apparent in the propor-tionalities of glucose, fructose, and sucrose in theleaves of boron-deficient and sufficient plants.

TABLE VPERCENT OF TOTAL PHOTOSN-YTHATE TRANSLOCATED AFTER20 MIN OF PHOTOSYNTHESIS AND 10 MIN OF DARKNESS'WITH 40 MICROCURIES OF C'4O2. (EACH VALUE FROM A

SAMPLE COMPOSED OF DUPLICATE PLANTS)

DAYS ON NO BORON 0.1 PPM OF %/cI INCREASETREATMENT ADDED BORON ADDED DUE TO BORON

2 0.24 2.41 9004 0.14 0.28 1006 2.21 2.98 358 0.77 1.60 108

10 0.24 0.64 16714 1.18 1.66 49

Radioautographs of chromatograms of extracts ofplants exposed to C1402 for 20 min indicate(d that themajority of the photosynthate soluble in 80 % alcoholwas represented by glucose, fructose, and sucrose inthe exposed leaf in both boron-deficient and sufficientplants. Of the translocation products, extracted fromboron-deficient plants, sucrose was by far the domi-nant constituent. The translocation products ofboron-sufficient plants were not determined.

It is evident that the lack of boron decreased theamount of translocation to all parts of the plant soonafter the boron supply was removed. Though thedetails of the action of boron in the translocation ofcarbohydrates are not yet clear, a mechanism similarto that proposed by Gauch and Dugger (6) wouldagree with the experimental evidence presented here.

SUMMARYA role of boron in the translocation of sugars was

verified by these experiments with tomato plants insand culture.

Sugar sprays applied to the tips of boron-deficientplants did not prevent death of the tips, but radio-active sucrose was more rapidly translocated inboron-deficient plants not yet showing morphologicalsymptoms in the presence of 50 ppm of boron than inthe absence of added boron. Once morphologicalsymptoms of the deficiency were visible, sucrose up-take and translocation were reduced and appliedboron did not aid in the distribuition of the appliedsugar.

After 4 hours of exposure to C140, a grealter per-centage of the photosynthate was translocated inboron-sufficient plants than in those showing borondeficiency symptoms. This was more apparent in thebasal than in the apical portions of the plant.

After 20 min exposure to C1402, distribution ofC14 was found to decrease logarithmically with dis-tance up and down the stem from the point of attach-ment of the exposed leaf. Boron-sufficient plantstranslocated a greater percentage of the photosyn-thate as early as 4 days after the boron supply wasremoved in one experiment and as early as 2 d(las inanother experiment. With only one exception, thiswas found throughout the 14 days of experimentation.

Chromatographically there were no apparent dif-ferences in the concentrations of amino acids and or-ganic acids in the two kinds of plants, and sugarswere in the same proportions. Presumably sugar wasmoving primarily in the form of sucrose.

LITERATURE CITED1. AGULHON, H. Emploi du bore comme engr ais

catalytique. Compt. rend. acad. sci., France 150:288-291. 1910.

2. ALEXANDER, T. R. Anatomical and physiologicalresponses of squash to various levels of boron sup-ply. Bot. Gaz. 103: 475-491. 1942.

3. BLOCK, R. J., LESTRANGE, R., and ZWEIG, R. PaperChromatography. Pp. 1-195. Academic Press Inc.,New York 1952.

4. CHANDLER, F. B. Mineral nutrition of the genus

16




Brassica with particular reference to boron. Ph.D.thesis, University of Maryland, College Park,Maryland 1939.

5. DEN-ISON, F. W., JR. and PHARES, E. F. Rapidmethod for paper chromatography of organicacids. Anal. Chem. 24: 1628. 1952.

6. GAUCH, H. G. and DUGGER, WV. M., JR. The role ofboron in the translocation of sucrose. PlantPhysiol. 28: 457-466. 1953.

7. GAUCH, H. G. and DUGGER, W. M., JR. The physio-logical action of boron in higher plants: A reviewand interpretation. Agr. Expt. Sta., Maryland,Tech. Bull. A 80. 1954.

8. GAUCH, H. G. and WADLEIGH, C. H. A new type ofintermittently irrigated sand culture equipment.Plant Physiol. 18: 543-547. 1943.

9. HATCHER, J. T. and Wr.cox, L. V. Colorimetricdetermination of boron using carmine. Anal.Chem. 22: 567-569. 1950.

10. JOHNSTON, E. S. and DORE, W. H. The influence ofboron on the chemical composition and growth ofthe tomato fruit. Plant Physiol. 4: 31-62. 1929.

11. JOHNSTON, E. S. and FISHER, P. L. The essentialnature of boron to the growth and fruiting of thetomato fruit. Plant Physiol. 4: 387492. 1930.

12. MITCHELL, J. W., DUGGER, W. M., JR., and GAUCH,H. G. Increased translocation of plant growthmodifying substances due to application of boron.Science 118: 354-355. 1953.

13. MITCHELL, J. WV. and LINDER, P. J. Some methodsused in tracing radioactive growth-regulating sub-stances in plants. Bot. Gaz. 112: 126-129. 1950.

14. SCHROPP, W. and ARENZ, B. tVber die Wirkungeiniger spurenelemente, insbesondere des Bors, aufdas Wachstum verschiedener Baumwollsorten.Phytopath. Zeits. 12: 366-404. 1939.

15. STRUCKMEYER, B. ESTHER and MACVICAR, R. Furtherinvestigations on the relation of photoperiod tothe boron requirement of plants. Bot. Gaz. 109:237-249. 1948.

16. VERNON, L. P. and ARNOFF, S. Metabolism of soy-bean leaves. IV. Translocation from soybeanleaves. Arch. Biochem. Biophys. 36: 383-393. 1952.

NECESSITY OF INDOLEACETIC ACID FOR THE DUPLICATIONOF CROWN-GALL TUMOR CELLS"12

RICHARD M. KLEIN3 AND HOWARD H. VOGEL, JR.THE NEW YORK BOTANICAL GARDEN, NEW YORK 58, NEW\ YORK, AND

DIVISION OF BIOLoGICAL AND MEDICAL RESEARCHI, ARGONNENATIONAL LABORATORY, LEMONT, ILLINOIS

The presence of a crown-gall tumor in vivo is fre-quently associated with numerous modifications of thegrowth behavior of the host. Included among theseare severe epinasty, suppression of the developmentof lateral shoots, delay in petiolar abscission, and in-creased cambial activity. Many investigators foundthat indoleacetic acid (IAA) could induce almostidentical abnormalities independent of the presence ofa tumor (1, 14). It was postulated by Link andEggers (18) that crown-gall tumors contained highconcentrations of IAA that were carried throughoutthe host plant and were responsible for the observedchanges. Indeed, bioassays of tomato plants demon-strated that there was much more auxin in tumortissues than in corresponding normal stem tissues (18).This report could not at the time be confirmed (24),but the present evidence supports the findings of Linkand Eggers. Although it was not then known whetherthe crown-gall bacteria synthesized the IAA presentin tumor tissues or whether it was formed in thetumor cells, DeRopp (3) later concluded that thetumor cells themselves were the primary source of theauxin. Both Kulescha (15) and Henderson andBonner (10) demonstrated that there was more IAAin the tissues of sterile tumors in vitro as compared

1 Received July 19, 1955.2 Work performed under the auspices of the U. S.

Atomic Energy Commission.3 Supported in part by a fellowship from the Ameri-

can Cancer Society as recommended by the Committeeon Growth, National Research Council.

with in vitro cultures of normal tissues and that IAAwas synthesized by tumor cells.

Attempts to prove that these high endogenouslevels of IAA are necessary for the duplication oftumor cells have failed since additions of IAA tocrown-gall tissue in vivo or in vitro were generallyinhibitory or without significant effect on tumor-cellduplication (3, 11, 15). The simplest way to demon-strate a positive role for IAA in the growth of crown-gall tissues would be to reduce the biologically effec-tive level of IAA with concomitant reduction ingrowth. Control rates of growth should be restoredby addition of this growth substance.

Two lines of attack on this problem have appeared.The first of these is the radiation technique discoveredby Skoog (28) and developed by Gordon (6, 7, 35).Here, controlled doses of ionizing radiation reduce theendogenous level of IAA, presumably by blocking itssynthesis. The doses of radiation used are not perma-nently inhibitory to other cellular processes, althoughhigher doses have profound effects on chromosomes,nucleic acid biosynthesis, and other processes (22, 23)which are not reversible with IAA. Levin and Levine(19) and Rivera (25) found that hard x-rays wouldprevent the growth of tumors on Ricinus as judged byincreases in tumor size or by microscopic examinationof the affected cells. Stapp and Bortels (29), how-ever, were unable to observe any reduction in tumorgrowth on tomato plants following x-irradiation.Recently, WVaggoner and Dimond (33) demonstratedthat ionizing radiations delaved the appearance of

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Documents

onPLANT PHYSIOLOGY showing morphological symptoms. There is some evi-dence (6, 12) that boron deficiency has an effect on the translocation of sugars, and possibly other organic compounds,