Effects of Carbon Dioxide Concentration on the Growth of Callistephus chinensis cultivar Johannistag

Carbon dioxide enrichment to 600 ppm increased the amount ofdry matter produced by Callistephus chinensis plants in growthcabinets with negligible mutual shading over a period of 18weeks. Further enrichment to 900 ppm showed smaller and morevariable increases. These effects were the result of a higherunit leaf rate of the treated plants. The direct effect on unitleaf rate was partly offset by a reduction in leaf-area ratio,and this was due almost entirely to the effect on specific leafarea with hardly any effect on leaf-weight ratio. Carbon dioxideaccelerated flower development by about a week at 600 ppm andsomewhat less at 900 ppm. The proportion of the total plantweight in the form of flowers showed a similar trend with timein all treatments and the relationship between flower-weightratio and dry-matter content of flowers was likewise similarfor all treatments, with the highest dry-matter contents ofabout 19 per cent associated with the highest flower-weightratios of about 0.44 for mature flowers. Carbon dioxide enrichmentsignificantly increased the dry-matter content of leaves. Theefficiency of energy conversion based on incident light anda twenty-four-hour cycle of 8 h light and 16 h dark for smallplants of 140–300 mg total dry weight (leaf areas of 50–120cm²) was about 4.7 per cent for the 325 ppm treatment, 6.3 percent for 600 ppm, and 5.5 per cent for 900 ppm. By referenceto some further experiments on the growth of C. chinensis cultivarJohannistag in glasshouse conditions, considerable adaptiveresponse to high and low light intensity was also demonstrated.     

The Effects of Copper Supply and Shading on Retranslocation of Copper from Mature Wheat Leaves

Plants of Gamenya wheat (Triticum aestivum L.) were grown inpots of a Cu-deficient sand at two levels of Cu (deficient andsufficient), and harvested on days 13, 22, 28 and 38. In 50per cent of the pots in each Cu treatment, the oldest leaf andleaf 2 of the main stem were shaded when they reached full expansion. The Cu content of the oldest leaf of Cu-sufficient, unshadedplants was high at day 13 and declined rapidly to day 38. Thatof Cu-deficient, unshaded plants was initially relatively lowand declined much more slowly, so that at day 38 it resembledthat of Cu-sufficient plants. Shading the oldest leaf acceleratedthe loss of its Cu in both Cu-deficient and Cu-sufficient plants.The effects of shading and of Cu supply on the loss of Cu fromthe oldest leaf paralleled their effects on the loss of N andchlorophyll. The results suggest that most of the Cu in theoldest leaf does not move out until the leaf senesces. In Cu-deficient plants retention of Cu by old green leaves accentuatedCu deficiency. The release of Cu, resulting from shading theold leaves of Cu-deficient plants, stimulated the growth ofnew leaves. In Cu-sufficient plants, shading depressed growth. copper, shading, retranslocation, wheat, Triticum aestivum L.     

An Analysis of Growth of Oil Palm Seedlings in Full Daylight and in Shade

Growth of seedling oil palms (Elaeis guineensis), in full daylightand under three levels of shade, was studied using growth analysistechniques. In full day-light, net assimilation rates (E_A) betweeno.15 and 0.32 g./dm.²/week were obtained associated with lowleaf-area ratios (F) giving relative growth-rates (R_W) rangingfromI I.8 to 3.2 per cent, per day. There were no indicationsof seasonal differences within the small range of values found. The plants take about 90 days to adapt to shade conditions becausethe mean plastochron is 24 days, and shading effects are beststudied on plants grown since germination under the shade treatments.Very different pictures of response to shade were obtained usingplants grown initially in full light followed by 90 days' shadebefore sampling compared with plants grown under shade sincegermination. In the latter, except at the lowest light levelused, I I.I per cent, of full day-light, there was very littleeffect of light on E_A or R_w, although the F values decreasedas light increased. Extrapolation of the F values to the extinctionpoint gave values similar to those obtained in another experimenton the effect of a number of shade levels on F. The physiological and ecological implications of these findings,particularly the low growth-rates and shade tolerance, are discussed.     

Photosynthesis by White Clover Leaves in Mixed Clover/Ryegrass Swards

Measurements of rates of net photosynthesis were made on singleBlanca white clover leaves on plants taken from a field-grown,mixed clover/perennial ryegrass sward during two regrowth periods. Net photosynthesis fell by 20 per cent in the first measurementperiod as leaf area index increased and the grass componentof the crop flowered, but did not change significantly in thesecond measurement period during which the grass remained vegetative. Leaves which had been artificially protected from shading inthe sward did not have significantly different photosyntheticcapacities from leaves in the undisturbed sward, even in thefirst measurement period. As leaf area index and sward height increased, successive cloverpetioles were longer, keeping the newly expanded leaves nearthe top of the sward where they received full light. It is suggestedthat it is this which allows successive clover leaves, unlikethose of vegetative grasses, to attain a high photosyntheticcapacity throughout a growth period. Trifolium repens, Lolium perenne, Photosynthetic capacity, shading, growth     

The Influence of Genes ar and n on Senescence in Pisum sativum L.

The effect of genes ar (violet flowers, small hilum) and n (thick,fleshy pod wall) on whole plant in senescence peas was examinedby comparing Ar- with arar and N- with nn plants in segregatingprogenies. Homozygosity for ar or n significantly delayed the time whenthe plants were ready for harvest of their entire seed crop.These genes did not delay either the onset of reproduction orthe onset of apical arrest in the first instance. However, whereasAr- N- plants almost invariably senesced and died as the firstseed crop matured, the majority of arar and/or nn plants entereda period of secondary growth and a further fruiting cycle. Comparedwith Ar- plants, arar plants had over twice as many pods andseeds but individual seeds were 58 per cent lighter and totalseed yield (wt) was 19 per cent less. Pod length was unaffected.Compared with N-plants, nn plants had shorter pods (16 per cent),fewer seeds per pod (21 per cent), smaller seeds (20 per cent)and a lower total seed yield (wt 14 per cent less). It appearsthat ar and n impose a lower metabolic drain per reproductivenode as a consequence of their effects on hilum anatomy andpod morphology, respectively. These mutants disrupt the normalpattern of monocarpic senescence by breaking the coordinationbetween apical arrest and subsequent events. The developingseed crop delimited by the first arrest fails to cause plantdeath, possibly because sink size is less than in normal counterparts. Pisum sativum L, garden pea, senescence, hilum, pod, seed size, genetics     

The Effects of Shading on the Yield Components of Six 'Leafless' Pea Genotypes

The effect of unshaded, 30 and 80 per cent shade conditionson the growth rate and yield composition of six ‘leafless’pea (afaf: stst) genotypes has been determined. No evidencefor a photoassimilate source limitation was found in the unshadedand 30 per cent shade treatments, but 80 per cent shade significantlyreduced the yield and the rate of d. wt and node productionof all the genotypes. Yield development was followed in each environment by determiningthe number of flowering nodes, the number of flowers producedper node, the pod number per node and the seed number per pod.The theoretical maximum for each of these yield components wasdetermined and compared with the actual level realized by theplant. Approximately 50 per cent of the theoretical potentialof each yield component was realized and this appeared to beindependent of the shade treatment. This stepwise reductionin potential yield throughout the development of the plant wassimilar to that reported for conventional pea plants. Pisum sativumL, ‘leafless’ peas, shading, growth rate, yield'components, source limitation     

Cell Cycle Responses to Red or Far-red Light, or Darkness, in the Shoot Apex of Silene coeli-rosa L. During Floral Induction

Twenty-eight-day-old plants of Silene coeli-rosa L. were maintainedin short days (SD) for 9 d (0–8) or exposed to 7 longdays (LD), or 7 SD with a 5 min exposure at 1700 h of each dayto far-red (FR), red (R) or 5 min FR/5 min R, or 7 dark-interrupted(di = 1700–1720 h) LD. Treatments were followed by twofurther SD. The mitotic index and G1 and G2 proportions weremeasured in the shoot apices of plants sampled at 2000 h ofeach day of each replicated treatment. Exposure to 7 LD (= 100per cent flowering) resulted in significant increases, relativeto the SD controls, in both the G2 proportion and the mitoticindex on d 0 to 3, 7 and 8. Five minute FR (= 0 per cent flowering)resulted in cell cycle responses similar to those in LD onlyfrom d 0 to 2. R and FR/R (both = 0 per cent flowering) didnot result in any increases in the G2 proportion in the apexapart from d 3 of FR/R. However 5 min FR/5 min R, and to a lesserextent 5 min R, did result in significant increases in the mitoticindex on d 0, 1, 7, and 8. diLD (= 8–10 per cent flowering)also prevented any significant increases in the G2 proportionon d 0 to 3, and 5 to 8 but the mitotic index was again higheron these days compared with control data. Thus the transitionto floral growth for 90 per cent of the plants is associatedwith changes in the cell cycle in the shoot apex measured asincreases in the G2 proportion at 2000 h of LD 0 to 3 and 7to 8. Silene coeli-rosa L., cell cycle, flowering, phytochrome, shoot apex     

Physiological and Ecological Studies in the Analysis of Plant Environment: XI. A Further Assessment of the Influence of Shading on the Growth of Different Species in the Vegetative Phase

In a further analysis of the effects of varying light intensityon growth and development in the vegetative phase the reactionsof thirteen herbaceous species have been recorded. In some experimentsthe degree of shading has been extended to 0.055 daylight, alevel near or below the compensation point. For Lathyrus maritimus, Trifolium pratense, and Vicia faba,the net assimilation rate is directly related to the logarithmof the light intensity, but for Helianthus annuus, T. repent,T. hybridum, Medicago sativa, Phaseolus multiflorus, and Loliummultiflorum the relationship, though curvilinear, is not logarithmic.It is concluded that for all species the assimilation rate ofunshaded plants was limited by light even though in high summerthe recorded light energy between 4,000–7,000 A averaged1,900–2,200 foot-candles. For all these species between daylight and 0.12 daylight theleaf-area ratio rises as the intensity decreases and in generalthe trend is logarithmic. When the degree of shading is increasedto 0.055 daylight the logarithmic relationship still holds forL. maritimus and V. faba though this level is below the compensationpoint. For other species, such as P. multiflorus andH. annuusthe trend may be reversed below 0.12 daylight and the ratiothen falls. When the light intensity is reduced from daylight to 0.5 daylight,then for the species already cited and for Lolium perenne, Phleumpratcnse, and Festuca pratensis the relative growth-rate isinvariably depressed. At 0.055 daylight the relative growth-ratenever exceeded 1 per cent. per day. For L. perennet, P. pratense,and Dactylis glomerata the reactions to shading of ‘hay’and ‘grazing’ strains were different. The ecological and physiological implications of these findingsare discussed.     

Effect of Defoliation on the Growth and Yield of Wheat

The effect of removal of the fifth (L₁), fifth and sixth (L₂) and fifth, sixth and seventh leaves (L₃) from the main shoot and of similar number of leaves from the primary and secondary tillers, on the growth and yield of two varieties of wheat, was investigated. The plants were grown in pots under natural conditions. Defoliation did not affect tillering, ear number, and number of spikelets per ear. The area of the last 3 leaves was reduced only in L₃. Defoliation reduced the growth of stem up to the flag leaf stage but thereafter there was a remarkable recovery in increase in height and dry weight. The grain yield of the main shoot was affected relatively more than that of the primary and secondary tillers by defoliation. The grain yield per plant was reduced by 5 per cent in L₁, and L₂ and by 11 per cent in L₃. The bearing of these observations on productivity per unit area is indicated and it is suggested that a plant with two fewer leaves per shoot may suffer less from mutual shading of leaves and hence prove more efficient in a dense community.     

The Effect of Source-Sink Alterations on Soybean Seed Growth

Soybeans (Glycine max L. Merrill) were grown in the greenhouseand in the field to investigate the effect of variations inthe assimilate supply during the linear phase of seed developmenton the rate and duration of growth of individual seeds. Increasedassimilate supplies, created by partial fruit removal, increasedrates of dry matter accumulation, duration of seed growth, andfinal seed size (weight per seed). Reductions in the supplyof assimilate to the developing seed, created by shading (60per cent) the plants during the linear phase of seed development,lowered seed growth rate but did not affect final seed sizebecause of a longer duration of seed growth. Nitrogen stressduring seed development, created by removing N from the nutrientmedium, did not affect seed growth rate but shortened the durationof seed growth and reduced final seed size. The data indicatethat the growth characteristics of soybean seed are influencedby the supply of assimilate to the seed during the linear phaseof seed development. Glycine max L., soybean, seed growth rate, duration of seed growth, effective filling period     

Defoliation in White Clover: Regrowth, Photosynthesis and N2 Fixation

Single plants of white clover, grown in a controlled environmentand dependent for nitrogen on fixation in their root nodules,were defoliated once by removing approximately half their shoottissue. Their regrowth was compared with the growth of comparableundefoliated plants. Two similar experiments were carried out:in the first, plants were defoliated at 2.5 g, and in the secondat 1.2 g total plant d. wt. Defoliation reduced rate of N₂ fixation by > 70 per cent,rate of photosynthesis by 83–96 per cent, and rate ofplant respiration by 30–40 per cent. Nodule weights initiallydeclined following defoliation as a result of loss of carbohydratesand other unidentified components. No immediate shedding ofnodules was observed but nodules on the most severely defoliatedplants exhibited accelerated senescence. The original rates of N₂ fixation were re-attained after 5–6or 9 d regrowth, with increase in plant size at defoliation.In general, the rate of recovery of N₂ fixation was relatedto the re-establishment and increase of the plant's photosyntheticcapacity. Throughout the growth of both defoliated and undefoliatedplants nodule respiration (metabolism) accounted for at least23 ± 2 per cent of gross photosynthesis. The unit ‘cost’of fixing N₂ in root nodules, in terms of photosynthate, appearedto be unaffected by defoliation, except perhaps for plants veryrecently defoliated. Similarly, the percentage nitrogen contentsof shoot, root and nodules of defoliated plants became adaptedwithin a few days to those characteristic of undefoliated plants. Trifolium repens, white clover, N₂ fixation, defoliation, photosynthesis, respiration     

Distribution of Nitrogen during Growth of Sunflower (Helianthus annuus L.)

The accumulation, distribution and redistribution of dry matterand nitrogen is described for Helianthus annuus L. cv. Hysun21 grown on 6 mM urea in glasshouse culture. Seed dry matterand nitrogen were transferred to seedlings with net efficienciesof 40 and 86 per cent respectively. At flowering, the stem hadmost of the plant's dry matter and the leaves most of its nitrogen.About 35 per cent of the plant's nitrogen accumulated afterthree-row anthesis. The amount of protein in vegetative parts,especially leaves, declined after flowering. Concentrationsof free amino compounds also decreased during growth. Matureseeds had 38 per cent of the total plant dry weight and 68 percent of the total nitrogen. Seeds acquired 33 per cent of theirdry matter and nitrogen from redistribution from above-groundplant parts. The stem was most important for storage of carbohydrate,leaves the most important for nitrogen. Over 50 per cent ofthe nitrogen in the stem and leaves was redistributed. Plantsthat received 6 mM nitrate accumulated more dry matter thanurea-grown plants. Seeds from nitrate-grown plants were heavier(58 mg) than those of urea-grown plants (46 mg), and their percentageoil was greater (50 and 41 respectively). The amount of nitrogenper seed was the same. Little or no urea was detected in xylem sap of plants suppliedwith 5 mM urea, but it was detected in sap of plants which received25 mM. Concentrations of urea and amino compounds in the sapdecreased up the stem. Plants supplied with nitrate had mostof the nitrogen in xylem sap as NO₂^–, suggesting littlenitrate reduction in roots. Plants grown on 6 mM nitrate andchanged to high levels of urea-nitrogen for 14 days still hadhigh levels of nitrate; little nitrate remained in plants receivinglow levels of urea. When urea is applied in irrigation waterto field-grown sunflower, the nitrogen is subsequently takenup as nitrate due to rapid nitrogen transformations in the soil. Helianthus annuus L., sunflower, urea, nitrate, nitrogen transport, xylem sap, nitrogen accumulation nitrogen distribution     

The Stability of the Growth Pattern of Young Apple-trees under Four Levels of Illumination: With four Figures in the Text

As part of a programme on the characterization of the growthpattern of the apple-tree, uniform I-year-old plants carryingtwo new shoots were grown for a season under 100, 78, 41, or24 per cent, natural light. Weights of leaf, new stem, old stem,and root were determined by sampling on 6 occasions. The dryweightincrements over the whole season ranged from 17 to 151 g. ofwhich, in full light, 22 per cent, was leaf and 22 per cent,was root; in deep shade, 32 percent, was leaf and 8 per cent,was root; and under all conditions 56–60 per cent, wasstem. These percentages were the cumulative result of currentrates of growth of leaf, stem, and root over the whole growingperiod. The rates were not constant relative to one another,but the much greater quantity of growth made over the period100–200 days from bud-break swamped earlier differences.All treatments showed the same basic pattern of growth withminor differences increasing with the intensity of shading.These differences are discussed in relation to utilization ofreserves and the demands of the various regions of the plant.The response to shading was analysed into the effects of reducedlight interception, increased leaf dispersion, increased leafproportion, reduced length of growing season, and lighter leafweight at the beginning of the 20-leaf stage. The result ofthese factors was a doubling of the growth expected in the absenceof response. It was concluded that the pattern of growth isstable, and the conditions for the perpetuation of such stablepatterns as a necessary qualification for tree growth are brieflydiscussed.     

The Distribution of Chromosome Races of Ranunculus ficaria L. in the British Isles

The chromosome numbers of 889 plants from 222 British populationsof Ranunculus ficaria were counted. 66.1 per cent of the populationscontained diploids (49.1 per cent of plants), 4.1 per cent containedtriploids (5.5 per cent of plants) and 43.2 per cent tetraploids(45.4 per cent of plants); 13.1 per cent of the populationscontained two or more polyplotypes. At the fruiting stage, tetraploidplants can be reliably distinguished from diploids by the presenceof axillary bulbils in the tetraploids and their absence inthe diploids. The production of well-developed heads of achenes,which is more characteristic of the diploids than of the tetraploids,is a less reliable character. Diploid plants are widespreadthroughout the British Isles but tetraploids are more commonin the east than in the west; 17.6 per cent of the diploid plantshad B-chromosomes and these plants were virtually confined tosouthern England and the Midlands. The occurrence of triploidsand of mixed populations of diploids and tetraploids are bothshown to be more common than previously supposed.     

Studies in the Nutrition of Apple Rootstocks: II. Effects of Concentration of Iron in the Nutrient Solution on Growth and Chlorophyll Content

Rooted one-year shoots were grown for one season by sprayingtheir roots with nutrient solution. Iron supplied as Fe-EDTAat four concentrations resulted in plants which were respectively(a) severely chlorotic, (b) mildly chlorotic, (c) dark greenand healthy (controls), and (d) dark green but with slight reductionin growth. Severely deficient plants showed 40–70 per cent reductionsin growth as measured by fresh weight, shoot length, diameterincrease, leaf area, net assimilation and relative growth-rates.Dry weights were reduced 70–80 per cent and of the totaldry-weight increment a greater proportion remained in the leaves,which had a lower dry weight and higher water content per unitarea. However, because the initial old stem formed a greaterproportion of the total dry weight, the leaf area ratio remainedabout 11 per cent lower than in the controls. Severely deficientplants had, per unit of chlorophyll, a higher dry-weight increaseand net assimilation rate than the controls. Mild deficiency caused 10–20 per cent reductions in growthand net assimilation rate; the leaf area ratio was normal. Possible mechanisms of the effects of low iron supply are discussed,while the small growth reduction at the highest Fe-EDTA concentrationis attributed to chelate toxicity     

Effect of Shading on the Regrowth of Lolium perenne Swards in the Field

Simulated swards of Lolium perenne cv. S.23 growing in the fieldwere shaded at various stages of regrowth during August andSeptember, when insolation was most likely to be limiting. Reductionof ambient illumination to 50 per cent for periods up to 24days had little effect on the current production of herbage(mainly leaf blade), which progressed at the expense of rootand stubble growth. After defoliation, however, previously shadedswards transferred to full light regrew relatively slowly. Leafarea and leaf extension were increased by shading, but leafappearance rates were only slightly affected. Shading decreasedtiller densi ties, and hence stubble yields, but did not affectmean tiller weights. The dangers of relating herbage yield tocurrent rates of insolation and photosynthesis, and the relevanceof these findings to other grass varieties are discussed.     

The Effect of Fruit Shading on Yield in Pisum sativum L.

Fruits of Pisum sativum L. cv. Feltham First which initiatesonly one flower per flowering node, were selectively shadedunder varying levels of defoliation. The purpose of the experimentswas to ascertain whether the foliage could compensate for lossof the fruit's contribution to its own growth. There was evidenceof this, but fruit and seed weight per fruit and per plant werereduced by fruit shading at all levels of defoliation. The lossin yield due to shading suggested that the contribution fromthe fruit was at least 12 per cent. The number of seeds whichdeveloped to maturity was the yield component most affectedby treatment. There was no evidence to suggest that shadinghad a different quantitative effect on final weight at differentnodes, but it did increase flower abscission at the first foweringnode in an experiment done at low radiant exposure. In an experimentat higher radiant exposure, very few flowers abscised at theearlier nodes, but leaflet removal reduced final fruit yieldat the first flowering node to a greater degree than at thesecond. These differential responses could contribute to variabilityof seed size in a crop of vining peas. Pisum sativum, pea, fruit, pod, light, shading, photosynthesis, yield     

Studies in Dormancy of Sycamore: II. THE EFFECT OF DAYLENGTH ON THE NATURAL GROWTH-INHIBITOR CONTENT OF THE SHOOT

1. An investigation was made into effect of daylength conditionsof the inhibition content of first-year seedlings of sycamore(Acer pseudoplatanus). 2. The shoot apical regions and mature leaves were extractedwith 80 per cent. Aqueous methanol, fractionated by paper chromatographyin isopropanol/ammonia and assayed by the wheat-coleptile growthtest. 3. A growth inhibitor was present in all extracts at R_f 0.7.Higher levels of inhibitor were present in both apices and matureleaves of plants transferred to short-day conditions than ofthose maintained under long-days throughout. 4. These difference in inhibitor level can be detected after2–5 days of short-day treatment, Preceding any markedeffect of daylength on growth. 5. Evidence is adduced in support of the hypothesis that theinhibitors is produced in the leaves during darkness and istransported to the apex during the photoperiod.     

Accumulation and Distribution of Nutrients in Fruits of Castor Bean (Ricinus communis L.)

The nutrition of developing fruits of Ricinus communis was studiednear Perth, Western Australia, where the species grows as aweed on poor sandy soil. Fruits required 60 days to mature anddehydration of the capsule began 20 days before the seeds ripened.Mature seeds accumulated 49 per cent of the fruit dry matterand over 80 per cent of its P, Zn and Cu, 50–80 per centof its Mg, N, Fe and Mn, 41–46 per cent of its S and Caand 11–21 per cent of its K and Na. Losses of nutrientsfrom capsules during fruit ripening were: Zn, 73 per cent, P,42 per cent, Cu, 23 per cent and Mn, 8 per cent. Dry matter,N, K, S, Ca, Mg, Na and Fe were not withdrawn from capsules.Apparent retranslocation from capsules could have provided from6–28 per cent of the Zn, Mn, P and Cu in mature seeds.Seeds from plants on poor sandy soil were small but had adequatelevels of nutrients when compared with those from plants growingon a fertile loam. Concentrations of all nutrients except P were higher in youngcapsules than in young seeds, but levels of N, P, Mg, Fe, Znand Cu were higher in mature seeds than in mature capsules.The intake of most nutrients by fruits was out of phase withdry matter accumulation, especially in capsules, and the elementsappeared to accumulate in fruit parts independently of eachother. Glutamine accounted for over 85 per cent of the amino-Nin phloem sap destined for fruits. Potassium made up over 90per cent of the inorganic cations in phloem exudate. Of theminor elements in the exudate, Fe was present at highest concentrationand Cu at the lowest. The results showed that retranslocation from the capsule madea very small contribution to the nutrition of seeds. It is suggestedthat R. communis would require a sustained supply of soil nutrientsto ensure maximum seed yield, partly due to the restricted retranslocationof most nutrients from capsules. Ricinus communis L., castor bean, mineral nutrition, translocation, retranslocation     

Ovule and Seed Growth in Pollinated and Auxin-induced Parthenocarpic Watermelon Fruits

Watermelon ovaries of the varieties Early Yates, Sugar Babyand Candy Red were pollinated, stimulated to develop parthenocarpicallywith 0.05, 0.5 or 5 per cent 1-naphthylacetic acid (NAA) inlanolin or treated with lanolin alone (control). Pollinationproduced the greatest number of mature fruits in all varietiesbut the control treatments produced none. Some fruits reachedmaturity in response to all levels of NAA in the varieties EarlyYates and Sugar Baby. Candy Red produced fewer parthenocarpicfruits than Early Yates and Sugar Baby and responded to 0.5and 5 per cent NAA only. Ovule growth was stimulated in allcases except the controls. In Early Yates and Sugar Baby shrinkageand necrosis of ovules was observed at 21 days after treatmentwith 5 per cent NAA. In Candy Red little ovule growth occurredand all parthenocarpic ovules were shrunken and necrotic at21 days after treatment. It is suggested that ovule growth maybe important for early parthenocarpic fruit development. Citrullus lanatus, watermelon, fruit parthenocarpy, ovule, seed growth