Relationship between set, development and activities of growth regulators in tomato fruits

The actions of plant regulators in set and development of fruitsare well known. However, the presence and function of endogenoushormones in parthenocarpic fruits have still not been sufficientlyinvestigated. A comparison between seeded and seedless fruitsmakes it possible to obtain a more accurate understanding ofsome relationships between growth regulators and stages of fruitdevelopment. Endogenous auxin and gibberellin activity levelsand some growth parameters (fresh and dry weight, cell numberand cell volume, DNA content) have been determined in tomatofruits (Lycopersicon esculentum Mill.) of the cultivar Venturaand of its isogenic parthenocarpic mutant. In both genotypes,auxin and gibberellin are present in the first week after anthesis,though at different concentrations and with different patterns.These two activities are involved in fruit setting. The simultaneousoccurrence of maximum auxin concentration and of the beginningof cell enlargement, in both genotypes, shows that the activitypresent at this time starts fruit development and possibly determinesthe size of the fruits. High auxin activity is observed only in seeded fruits 20–40days after anthesis, and it is probably synthesized by seeds.Gibberellin activity is present, corresponding to the changein fruit development from the mature green to pink stages. (Received February 16, 1978; )     

CHANGES IN THE CONTENT OF GIBBERELLIN-LIKE SUBSTANCES IN RIPENING SEED AND POD OF LUPINUS LUTEUS

The amount of gibberellin-like substances in seed, pod, embryoand "endosperm" of Lupinus luteus in relation to their developmentwas studied by means of the rice seedling test. The amount of gibberellin-like substances per seed increasedremarkably at the first stage of development, when the growthof seed and pod was very slow, and attained its maximum at suchan early stage as the dry weight of seed reached a value ofonly 10 per cent and that of pod 28 per cent of their respectivemaximum levels. Changes in amount of gibberellin-like substancespresent in the pod were very closely related to the changesin growth of pod. Gibberellin-like substances equivalent to0.3 µg gibberellin A₃ per seed and 0.028 µg perpod were found at the 20th day after anthesis, and no activityin mature seed and 0.09 µg per pod at the 50th day. Noactivity was found in the embryo itself at all stages, indicatingthat the gibberellin-like substances in seed occur only in the"endosperm," i.e. in the tissues that will eventually form testain fully ripened stage. (Received December 18, 1962; )     

Inverse Correlation between ABA Content and Germinability throughout the Maturation and the In Vitro Culture of the Embryo of Phaseolus vulgaris

Prevost, I. and Le Page-Degivry, M. Th. 1985. Inverse correlationbetween ABA content and germinability throughout the maturationand the in vitro culture of the embryo of Phaseolus vulgaris.—J.exp. Bot. 36: 1457–1464. Changes in embryo abscisic acid (ABA) content during the maturationof the seed of Phaseolus vulgaris cv. Contender were followed,using a radio-immunoassay. The pattern of change is similarto that already described in several species: a rapid increase(from the 18th to 29th day after anthesis), was followed bya decrease, the ABA level being ten times lower on the 48thday than on the 29th. Embryos isolated from the 18th to the48th day after anthesis were able to ‘germinate’when cultivated on a mineral medium supplemented with sucroseand agar. The development pattern varied throughout the embryogenesisand could be correlated with the differentiation of the embryoat the time of isolation. Before germination could take place,we observed a lag phase, the duration of which could be correlatedwith embryo ABA content. As ABA content increased in the youngestembryos the duration of the lag phase increased. In the sameway, the number of days to germination was shown to diminishas ABA content decreased. Inverse correlation between ABA contentand germinability was thus demonstrated throughout the developmentof the embryo. During in vitro culture, free ABA content decreased in the embryoand reached low values a few days before germination occurred.So the beginning of root elongation in culture was again wellcorrelated with the disappearance of free endogenous ABA. Atransfer experiment inducing an earlier germination associatedwith a more limited development suggests that the lag phaseis associated with an active continuation of embryonic development Key words: Embryo maturation, abscisic acid, germinability     

Polyamine Content in Relation to Embryo Growth and Dedifferentiation in Barley (Hordeum vulgare L.)

Putrescine, spermidine, and spermine content were analysed inzygotic embryos of barley (Hordeum vulgare L.). Changes in polyaminecontent were observed during zygotic embryo growth. In two cultivars,‘Bomi’ and ‘Golden Promise’, the totalpolyamine content in the embryos was 2.6–2.9 nmol mg^–1fresh weight 10 d after anthesis, the highest content observed.It dropped to 1.3 nmol mg^–1 fresh weight 14 d after anthesis.This drop was caused by decreases in all three polyamine concentrations.From 14 to 35 d after anthesis the putrescine content continuedto decrease while the spermidine and spermine content increased,thus the total polyamine content remained constant until 35d after anthesis. The mutant ‘Ris? 1508’ showeda constant polyamine content around 1.3 nmol mg^–1 freshweight from 14 to 35 d after anthesis. The polyamine patternwas conserved in all three lines throughout the period of investigationshowing a spermidine content higher than putrescine contentwhich was, in turn, higher or equal to the spermine content.The polyamine content measured as nmol µg^–1 proteindecreased from 14 to 21 d post anthesis in all three lines,because the protein content (µg mg^–1 fresh weight)increased during the period. In dedifferentiating zygotic embryoscultured in vitro the putrescine content (nmol mg^–1 freshweight) rose by a factor of nine and the spermidine contentdoubled within the first week of cultivation, whereas sperminecontent did not change. For embryoderived calli a repeated patternof change in polyamine content was observed throughout the subculturingperiod. Key words: Polyamines, Hordeum vulgare L., embryo development     

Fruit growth and abscission in Macadamia imtegrifolia

Growth in diameter of fruits (follicles) of five cultivate of Macadamia integrifolia Maiden and Betche followed a single sigmoidal pattern. A rapid increase in fruit diameter began 2 to 3 weeks after anithesis and continued until weeks 14 to 16. No further increase in size was observed after 16 weeks. Growth in fresh weight of the two cnltivars observed also followed a single sigmoidal pattern. A rapid increase in fresh weight began 5 to 6 weeks after anthesis and continued until weeks 15 to 18. No further increase in fresh weight was evident after 18 weeks. Abscission of flowers and fruits occurred continuously from anthesis through fruit maturity and could be separated into three periods. The first period of abscission occurred in the first 2 weeks after anthesis and commonly involved over 90% of the flowers. The second period of abscission occurred from 3 to 8 weeks after anthesis and commonly involved over 80% of the initial set of small fruit. This period of abscission occurred prior to and concurrent with the rapid increase in growth. The third period of abscission was gradual and occurred from 9 weeks after anthesis until maturity at 28 to 30 weeks. Measurement of ethylene evolution by fruits showed a peak during weeks 3 and 4. This was prior to the peak in relative abscission rate at week 5. The fruit removal force increased from anthesis through week 12 and decreased from week 24 through maturity.     

Effects of CO2 Enrichment at Different Irradiances on Growth and Yield of Wheat: I. EFFECTS OF CULTIVAR AND OF DURATION OF CO2 ENRICHMENT

Wheat, Triticwn aestivum L., the winter cultivars Hobbit andCappelle-Desprez, and the spring cultivars Sicco and KJeiber,were grown in normal air or air enriched with CO₂ either outdoorsin a glass-roofed cage or in controlled environment rooms. Inneither the winter nor the spring wheat was growth increaseddue to enrichment with CO₂ before anthesis. Enrichment of thetwo winter wheat cultivars increased shoot dry weight significantlyat 15 d after anthesis but produced no significant increasein grain yield. With the spring cultivars there was a significantincrease in shoot dry weight by 18 d after anthesis and thegrain yield was also larger due to an increase in grain size.Shoot weight increased because the stems were larger, and therewas a diversion of assimilate from grain growth to late tillerproduction. Root tissue comprised less than 20% of the totaldry matter at anthesis (for all cultivars); effects of CO₂ enrichmenton root growth appeared to be less important than effects onshoot and ear growth. Growth and yield responses to CO₂ enrichmentwere observed (for the spring cultivars) at irradiances of both250 and 635 µE m^–2 s^–1, but the effects weregreater at the lower irradiance. Key words: CO₂ enrichment, Wheat, Cultivar     

The Effect of High Temperature at Different Stages of Ripening on Grain Set, Grain Weight and Grain Dimensions in the Semi-dwarf Wheat 'Banks'

Grain number in the wheat cultivar Banks was reduced by up to11 % with a rise in temperature from 21/16 °C to 30/25 °Cover a 10-d period immediately following first anthesis in general,the upper ‘d’ and ‘c’ florets were moreaffected by high temperature than the basal ‘a’and ‘b’ florets within a spikelet and florets fromthe upper spikelets were more sensitive than those lower onthe ear Grain weight and grain length at maturity were most affectedby a 10 d period of high temperature commencing 7–10 dafter anthesis However, if dry-matter accumulation between thestart of a treatment and grain maturity was used as a base forcomparison, the response was more uniform throughout development,with a peak in sensitivity 25 d after anthesis Although grainposition within an ear did not have a large effect on the responseto temperature, grains from the basal spikelets were more sensitivethan those from the apex, and the upper floret grains of a spikeletwere more sensitive to high temperature than those at the base There is a need to obtain, for a range of cultivars, more comprehensivedata on the effect of the timing and degree of temperature stressfollowing anthesis, for use in interpreting the response torising temperatures late in the development of the crop in thefield Triticum aestivum L, wheat, temperature, grain development     

Effects of repeated application of water stress on water status and growth of wheat

The effects on water status and growth of controlled cycles of water stress applied at various stages of development were studied on a semi-dwarf spring wheat (Triticum aestivum L.). The plants were grown in controlled environment chambers of the Duke University Phytetron at 24/18°C with a 12-h photo-period at about 600 μE m^?2 s^?1. Groups of plants were subjected to severe water stress by withholding irrigation, beginning at the 7th leaf, early anthesis, or early dough stages of development. A second cycle started 9 to 13 days after termination of the first cycle and maintained until the flag leaf water potential reached –25 bars at each of the growth stages. The lower leaves showed sign of wilting as indicated by curling in the first drying cycle at –7 bars and in the second cycle at –9 bars of leaf water potential during all stages of growth. Although these leaves recovered completely upon rewatering, onset of senescence was accelerated by three days in stressed plants. A preliminary drying cycle did not increase the ability of the plants to withstand subsequent stress because of severity of stress. Water stress of –25 bars at all three stages of growth reduced seed yield. The reduction was greater when a second stress cycle was also applied. Stress applied during early anthesis stage produced the smallest and the least number of seeds. The lack of osmotic adjustment probably was due to very rapid and severe development of water stress.     

Innervation of developing human taste buds. An immunohistochemical study

 Morphological changes in developing human gustatory papillae during the 6th to the 23rd postovulatory week have been studied. The general innervation pattern of taste papillae and taste bud primordia was revealed immunohistochemically using antibodies against protein gene product 9.5 (PGP9.5), neurofilament H (NFH), neurofilament L (NFL), neurone-specific enolase (NSE), and tubulin. The autonomic and somatosensory nerve supply has been investigated using antibodies against substance P (SP), calcitonin gene-related peptide (CGRP), tyrosine hydroxylase (TH), neuropeptide Y (NPY), the neuronal form of nitric oxide synthase (n-NOS), and, enzyme histochemically, NADPH-diaphorase. Nerve fibers approach the basal membrane of the lingual epithelium around the 7th postovulatory week and invade the epithelium of papilla-like structures at the 8th week, but some also penetrate the basal membrane of the non-papillary epithelium. They are in close contact with slender epithelial cells that are considered to be the taste bud’s progenitor cells. Early human taste buds situated at the anterior part of the tongue do not necessarily require a dermal (later fungiform) papilla. The NADPH-diaphorase reaction revealed positive results in dermal nerve fibers, but the immunohistochemical reaction against n-NOS was negative. Immunohistochemical detection of neuropeptides and vasoactive substances rendered negative results for developmental stages of 7–18 postovulatory weeks. By the 18th week, only SP was detected in dermal papillae, but not in the vicinity of taste buds’ primordia. Thus, autonomic and somatosensory nerves seem not to play a key role in formation and maintenance of early human taste buds. Accepted: 31 July 1997     

Nitrogen redistribution during grain growth in wheat (Triticum aestivum L.)

The flag leaf of wheat was examined for changes in quantity and activity of ribulose-bisphosphate carboxylase (RuBPCase; EC 4.1.1.39), in the proteolytic degradation of RuBPCase and other native proteins, and in the ultrastructure of the leaf cells during grain development. Proteolytic degradation of RuBPCase at pH 4.8 increased until 8–10 d after anthesis, then declined, and increased again 16–18 d after anthesis. The second peak coincided with the onset of a preferential loss of immunologically recognizable RuBPCase. The specific activity and number of active sites per molecule of RuBPCase did not change during senescence. Examination of ultrastructure with the electron microscope showed little change in the appearance of the mitochondria as the flag leaf aged. Prominent cristae were still evident 35 d after anthesis. In contrast, the chloroplasts showed a progressive disruption of the thylakoid structure and an increasing number of osmiophilic glubules. The double membrane envelope surrounding the chloroplast appeared intact until at least 20 d after anthesis. The tonoplast also appeared intact up to 20 d. At later stages of senescence of the leaf the outer membrane of the chloroplast adjacent to the tonoplast appeared to break but the inner membrane of the envelope appeared intact until at least 35 d after anthesis.Abbreviation RuBPCase ribulose-1,5-bisphosphate carboxylase (EC. 4.1.1.39) I=Waters et al. 1980     

Photoperiod and Temperature Regulation of Floral Initiation and Anthesis in Soya Bean

Floral development includes initiation of floral primordia andsubsequent anthesis as discrete events, even though in manyinvestigations only anthesis is considered. For ‘Ransom’soya bean [Glycine max (L.) Merrill] grown at day/night temperaturesof 18/14, 22/18, 26/22, 30/26, and 34/30 °C and exposedto photoperiods of 10, 12, 14, 15, and 16 h, time of anthesisranged from less than 21 days after exposure at the shorterphotoperiods and warmer temperatures to more than 60 days atlonger photoperiods and cooler temperatures. For all temperatureregimes, however, floral primordia were initiated under shorterphotopenods within 3 to 5 days after exposure and after notmore than 7 to 10 days exposure to longer photoperiods. Onceinitiation had begun, time required for differentiation of individualfloral primordia and the duration of leaf initiation at shootapices increased with increasing length of photoperiod. Whileproduction of nodes ceased abruptly under photoperiods of 10and 12 h, new nodes continued to be formed concurrently withinitiation of axillary floral primordia under photoperiods of14, 15 and 16 h. The vegetative condition at the main stem shootapex was prolonged under the three longer photoperiods and issuggestive of the existence of an intermediate apex under theseconditions. The results indicate that initiation and anthesisare controlled independently rather than collectively by photoperiod,and that floral initiation consists of two independent steps—onefor the first-initiated flower in an axil of a main stem leafand a second for transformation of the terminal shoot apex fromthe vegetative to reproductive condition. Apical meristem, intermediate apex, floral initiation, anthesis, photoinduction, Glycine max(L.) Merrill, soya bean, photoperiod, temperature     

Partitioning and Utilization of Photosynthate Produced at Different Growth Stages after Anthesis in Soybean (Glycine max L. Merr.): Analysis by Long-term 13C-Labelling Experiments

Yamagata, M., Kouchi, H. and Yoneyama, T. 1987. Partitioningand utilization of photosynthate produced at different growthstages after anthesis in soybean (Glycine max L. Merr.): Analysisby long term ¹³C-labelling experiments.—J. exp. Bot. 38:1247–1259. Soybean (Glycine max L. Merr. var. Akishirome) plants were allowedto assimilate ¹³CO₂ with a constant specific activity for 10h at different growth stages (a total of seven times at aboutone week intervals) after anthesis. The plants were harvestedperiodically until the time of full maturity and the partitioningof ¹³C into individual plant parts was investigated with anemphasis on the contribution of carbon assimilated at differentgrowth stages to the seed formation. Carbon assimilated at the middle to late seed-filling stagecontributed most to the seed production; one day contributionaccounted for 3–4% in total carbon of the seed at fullmaturity. Integrated contribution of carbon assimilated afteranthesis was estimated as 96% of the final seed carbon. An approximationbased on the temporal data of the incorporation of labelledcarbon into the seeds indicates that 77% of the final seed carboncame from direct transfer of current photosynthate from sourceleaves, which occurred within a few days after the photosyntheticfixation, while the rest originated from remobilization of carbonreserved mainly in leaves and stems plus petioles. In comparison with the total carbon accumulation in the seeds,protein carbon in the seeds was relatively more dependent onphotosynthate produced during the early period of reproductivegrowth stage, whereas lipid carbon was more dependent on photosynthateproduced during the later reproductive stage. Key words: Photosynthate partitioning, soybean (Glycine max L. Merr.), ¹³CO₂ assimilation, seed formation     

Differential Alterations in Metabolic Pattern of the Spliceosomal UsnRNAs during Pre-Malignant Lung Lesions Induced by Benzo(a)pyrene: Modulation by Tea Polyphenols

The differential alterations of the spliceosomal UsnRNAs (U1, U2, U4, U5, and U6) were reported to be associated with cellular proliferation and development. The attempt was made in this study to analyze the metabolic pattern of the spliceosomal UsnRNAs during the development of pre-malignant lung lesions induced in experimental mice model system by benzo(a)pyrene (BP) and also to see how tea polyphenols, epigallocatechin gallate (EGCG) and epicatechin gallate (ECG), modulate the metabolism of these UsnRNAs during the lung carcinogenesis. No significant changes in the level of the UsnRNAs were seen in the inflammatory lung lesions at 9th week due to treatment of BP. However, there was significant increase in the level of U1 (∼2.5 fold) and U5 (∼47%) in the hyperplastic lung lesions at 17th week. But in the mild dysplastic lung lesions at 26th week, the level of UsnRNAs did not change significantly. Whereas, in the dysplastic lung lesions at 36th week there was significant increase in the level of the U2 (∼2 fold), U4 (∼2.5 fold) and U5 (∼2 fold). Due to the EGCG and ECG treatment the lung lesions at 9th week appeared normal and in the 17th, 26th, and 36th week it appeared as hyperplasia. The level of the UsnRNAs was significantly low in the lung lesions at 9th week (only U2 and U4 by EGCG), at 17th week (only U1 by EGCG/ECG), at 26th week (U1 by ECG; U2, U4 and U5 by EGCG/ECG) and at 36th week (U1 by ECG, U2 and U4 by EGCG/ECG). Whereas, there was significant increase in the level of U5 (by EGCG/ECG) and U6 (by EGCG only) in the lung lesions at 36th and 26th week respectively. This indicates that the metabolism of the spliceosomal UsnRNAs differentially altered during the development of pre-malignant lung lesions by BP as well as during the modulation of the lung lesions by the tea polyphenols.     

Calcium distribution in fertilized and unfertilized ovules and embryo sacs of Nicotiana tabacum L.

Potassium antimonate was used to localize Ca²⁺ in tobacco ovules from 0 to 7 d after anthesis in pollinated and emasculated flowers. Antimonate binds “loosely bound” Ca²⁺ into calcium antimonate; less-soluble forms are unavailable and free calcium usually escapes. Ovules are immature at anthesis. Abundant calcium precipitates in nucellar cells surrounding the micropylar canal. A difference between calcium in the two synergids emerges at 1 d, which is enhanced in pollinated flowers. The future receptive synergid accumulates more precipitates in the nucleus, cytoplasm and cell walls. After fertilization, micropyle precipitates diminish, and the ovule is unreceptive to further tube entry. In emasculated flowers 6 d after anthesis, ovular precipitates essentially disappear; however, flowers pollinated at 4–5 d and collected 2 d later largely restore their prior concentration of precipitates. Ovular precipitates occur initially in the nucellus, then the embryo sac, and finally the synergid and micropylar filiform apparatus. Possibility, calcium is released from the embryo sac, although no structural evidence of exudate formation was observed. Calcium precipitates in the ovule correlate with the ability of the ovule to be fertilized, suggesting that successful pollen tube entry and later development may require calcium of the class precipitated by antimonate. Received: 14 August 1996 / Accepted: 9 October 1996     

Separation and Some Properties of Large and Small Amyloplasts throughout Development in Barley Endosperm

A method is described whereby amyloplasts from immature barley (Hordeum distichum L.) endosperm could be separated into two populations of large and small amyloplasts at all stages of development. The small amyloplasts had more amylopectin than the large at early stages, but by 60 days after anthesis, the large had the greater proportion of amylopectin. Starch synthetase activity was associated with both types of amyloplast. The nucleotide specificity of the starch synthetase associated with each population varied independently throughout development. At 25 days after anthesis, the large amyloplasts were more susceptible than the small to α-amylolysis; however, at 38 and 60 days, the small amyloplasts became more susceptible.     

Role of antioxidative system during the development and senescence of cucumber fruit

The oxidative processes and antioxidative system in cucumber (Cucumis sativus L.) fruit were determined during development and senescence. Four distinct developmental stages could be delineated during fruit maturation: immature (3–8 d after anthesis, DAA), mature (9–16 DAA), breaker (17–22 DAA), and yellow (35–40 DAA). The electrolyte leakage, malondialdehyde content, superoxide anion production rate, and hydrogen peroxide content increased continuously during fruit development and senescence. Superoxide dismutase and peroxidase activities consistently increased during fruit maturation, and the catalase activity displayed a single peak at the mature stage. Ascorbate peroxidase and glutathione reductase activities declined during fruit development, but both were activated in yellow fruit. Monodehydroascorbate reductase activity declined and dehydroascorbate reductase (DHAR) activity increased during fruit growth. DHAR was repressed in yellow fruit. Ascorbate dramatically accumulated and its redox state increased, whereas glutathione was degraded and its redox state declined, with fruit maturation.     

Gibberellin-like substances and indole type auxins in developing grains of normal- and high-lysine genotypes of barley

Changes in gibberellin-like activity and content of indole type auxins were investigated during grain development of the two high-lysine barley (Hordeum vulgare L.) genotypes Sv 73608 and Risø 1508, and their corresponding normal cultivars Mona and Bomi. A peak in gibberellin-like activity was found in developing grains of the normal cultivars about 18 days after anthesis, whereas the grains of the high-lysine genotypes showed a two to five times higher maximum about 3–4 days later. The auxin content of the cultivar Bomi showed a maximum between the 22nd and the 29th day after anthesis, whereas, throughout their development the grains of the mutant Risø 1508 exhibited only about ¹/10 of the maximum level of auxin found in the grains of Bomi. The normal cultivar Mona also displayed higher contents of auxin than the high-lysine genotypes Sv 73608, particularly at the later stages of grain growth, but the differences in concentration were considerable smaller than for the pair ‘Bomi’—‘Risø 1508’. It is suggested that auxins play an important role in the development of barley grains.     

Effect of ovular receptivity on seed set and fruit development in cucumber (Cucumis sativus L.)

Summary Seed set and fruit development in cucumber (Cucumis sativus L.) were studied in relation to female flower receptivity from day — 2 before anthesis to day + 2 after anthesis. The female cucumber flower is protogynous. The pistil was receptive 2 days before anthesis. The iso-electric focusing (IEF) patterns of the stigma/style proteins, were identical from day -5 to day +2. In pollinated flowers in vivo germination and pollen-tube growth in the ovary were affected by pistil age from day -2 to day +2. In addition, differences in sectorial filling in full seeds were observed within the fruits. A negative correlation was observed between the frequency of fertilized ovules in the pedoncular part of the fruit and ovary length at the time of pollination. In the whole fruit, significant differences in the number of full seeds and fruit size at maturity were found, and these were observed to be correlated with the various stages of female flower maturation at pollination. The day -2 and day +2 stages yielded the smallest fruits with few full seeds compared to the day -1, day 0 and day +1 stages, which had the biggest fruits and a large number of full seeds. A strong positive correlation was found between total seed number (including full and empty seeds), fruit length and weight at maturity. All these results suggest that both seed set in the different parts of the fruit and fruit development are controlled by ovular receptivity rather than by stigma/style receptivity.     

Changes in Nuclear DNA Content of Endosperm Cells During Grain Development in Rice (Oryza sativa)

Morphological, cytological and quantitative DNA changes associatedwith endosperm development in rice caryopsis were investigated.Following a brief free-nuclear phase, the endosperm became cellularby the 4th d after anthesis. While the mean length and breadthof grain attained maximum values at about 10, d after anthesis,f. wt of the whole grain, and of the endosperm separately, continuedto increase until about 16 d after anthesis. Cell divisionsin the endosperm continued until 10 d and following stabilizationof the cell number, the nuclei attained irregular shapes. Thesize of the nuclei and nuclei and the amount of nuclear DNAvaried considerably during endosperm development. The endospermnuclei did not retain the expected 3C–6C DNA level afterthe first few rounds of division and nuclei having more than30C DNA were frequent 8 d past anthesis. The highest C valuerecorded was 74C in a 16-d-old endosperm cell. Oryza sativa, rice, caryopsis, endosperm, cell number, nuclear area, nuclear DNA content, endoreduplication