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1.
In developing seeds of mustard ( Brassica juncea L. cv. RLM 198) the period between 20 and 30 days after fertilization (DAF) was identified as the period of active lipid biosynthesis, although dry matter continued to accumulate until maturity. The period of lipid synthesis was associated with a decrease in starch, soluble sugars and protein, thus, giving rise to precursors for the biosynthesis of lipids. Besides decreasing the dry matter content (on both % and seed basis), Zn and S deficiency caused a significant ( P > 0.05) reduction in oil content. As compared to control, the decrease in oil content was 11, 12 and 18% at 30 DAF and 4, 9 and 16% at maturity in Zn, S and (Zn+S) deficient treatments, respectively. Throughout the period of seed development, a significant decrease in starch and protein with a slight accumulation of soluble sugars was observed due to deficiency of Zn or S. The rate of [l-14 C]-acetate incorporation into total lipids, which was maximal at 30 DAF, also displayed a significant decrease due to the abovementioned mineral deficiencies. Addition of Zn or S in vitro, enhanced the lipid synthesis at all stages of seed development. Under Zn and S deficiency, the phospholipids increased from 10 to 30 DAF and then declined until maturity. However, the proportion of glycolipids and free fatty acids increased, with a corresponding decrease in total glycerides. Further, in deficiency treatments, there was an increase in 22:1 with a corresponding decrease in 18:1, 18:2 and 18:3 in developing and mature mustard seeds. 相似文献
2.
The Development of Tomato Root System in Relation to the Carbohydrate Status of the Whole Plant 总被引:4,自引:1,他引:3
The decrease in growth rate of the root system or complete cessationof its growth in developed, fruit-bearing tomato plants areknown phenomena. It has been suggested that a limited supplyof carbohydrates to this organ, due to its relative weaknessin competition with the flowers and developing fruitlets isthe main cause for these disorders. This theory was tested inthe present study with plants grown in an aerohydroponic systemup to the appearance of 1213 trusses per plant, 172 dafter transplanting. The changes in the contents of carbohydratesin the various organs during this period were monitored. Theconcentrations of soluble sugars and starch in the leaves increasedwith the increase in truss number. The upper stem was foundto contain more carbohydrates than the lower stem, while nosignificant changes in the concentration of these compoundscould be detected in the roots throughout the experiment. Nevertheless,120130 d after transplanting, the roots of the plants,bearing five to six trusses and two to three inflorescences,ceased growing and remained at the same or a slightly reducedsize for another 4050 d. Calculations show that at thestage of five to six trusses, 38 g total soluble sugars and35 g starch were stored in the vegetative organs. Therefore,it seems unlikely that carbon deficiency caused by the competitionwith the reproductive organs (mainly developing fruits), affectedthe root growth. Instead, it is suggested that some other factoris responsible. Lycopersicon esculentumMill; carbohydrates; root growth rate; sink-source relationship; soluble sugars; starch 相似文献
3.
Background and Aims
Previous studies have reported effects of pollen source on the oil concentration of maize (Zea mays) kernels through modifications to both the embryo/kernel ratio and embryo oil concentration. The present study expands upon previous analyses by addressing pollen source effects on the growth of kernel structures (i.e. pericarp, endosperm and embryo), allocation of embryo chemical constituents (i.e. oil, protein, starch and soluble sugars), and the anatomy and histology of the embryos.Methods
Maize kernels with different oil concentration were obtained from pollinations with two parental genotypes of contrasting oil concentration. The dynamics of the growth of kernel structures and allocation of embryo chemical constituents were analysed during the post-flowering period. Mature kernels were dissected to study the anatomy (embryonic axis and scutellum) and histology [cell number and cell size of the scutellums, presence of sub-cellular structures in scutellum tissue (starch granules, oil and protein bodies)] of the embryos.Key Results
Plants of all crosses exhibited a similar kernel number and kernel weight. Pollen source modified neither the growth period of kernel structures, nor pericarp growth rate. By contrast, pollen source determined a trade-off between embryo and endosperm growth rates, which impacted on the embryo/kernel ratio of mature kernels. Modifications to the embryo size were mediated by scutellum cell number. Pollen source also affected (P < 0·01) allocation of embryo chemical compounds. Negative correlations among embryo oil concentration and those of starch (r = 0·98, P < 0·01) and soluble sugars (r = 0·95, P < 0·05) were found. Coincidently, embryos with low oil concentration had an increased (P < 0·05–0·10) scutellum cell area occupied by starch granules and fewer oil bodies.Conclusions
The effects of pollen source on both embryo/kernel ratio and allocation of embryo chemicals seems to be related to the early established sink strength (i.e. sink size and sink activity) of the embryos.Key words: Zea mays, maize, pollen, kernel, embryo, endosperm, oil, protein, starch, soluble sugars 相似文献4.
The purpose of this study was to explore the effect of dietary fats on the hepatic fatty acid profile of mice liver after
partial hepatectomy and to observe a correlation with changes in element content. Male Balb/C mice were divided into three
groups: the control animals fed a standard diet (FSD), the FOO group fed a diet enriched with 5% olive oil, and the FCO group
fed a diet enriched with 5% corn oil. Hepatic fatty acid and element content were analyzed within each group in intact animals
and on d 1, 2, and 7 after partial hepatectomy. During the regenerative process, proportions of 18∶1n−9 and 18∶3n−6 substantially
increased in the FSD diet, correlating with the Zn level. On the other hand, 20∶4n−6 and 22∶6n−3 decreased on d 1 and 2. Consequently,
a significant increase in the n−6: n−3 ratio was found in these animals. In the FOO diet, a decreased polyunsaturated fatty
acid/monounsaturated fatty acid (PUFA/MUFA) ratio was related to a significant decrease in PUFA content, mainly the results
of decreased 30∶3n−6 and 20∶4n−6. The proportion of 18∶1n−9 was highly increased when compared with other diets and remained
high during the regeneration. Furthermore, the n−6∶n−3 ratio was increased on d 2 and 7. Zn increased on d 1 and 2, and Fe
increased on d 2. Feeding with corn oil generally induced an increase in the PUFA n−6 series, compared with other diets. The
PUFA n−3 series decreased and the 18∶1n−9 increased on d 1, compared to intact animals. Consequently, the n−6∶n−3 ratio was
elevated during the regeneration. Zn increased on d 1 and 2, whereas Fe remained unchanged until d 7, when it decreased. Decreased
20∶4n−6 on d 1 and 2, as well as Cu on d 7, and increased Zn in the first 2 d were common to all three diets. These findings
suggest that some significant signals transmitted during the regenerative process have induced alterations in the fatty acid
composition and changes in the liver element content, which can be modified by the diet. 相似文献
5.
The effect of increasing concentrations of Al2(SO4)3 in situ on the content of starch, sugars and activity behaviour of enzymes related to their metabolism were studied in growing
seedlings of two rice cvs. Malviya-36 and Pant-12 in sand cultures. Al2(SO4)3 levels of 80 and 160 μM in the growth medium caused an increase in the contents of starch, total sugars as well as reducing
sugars in roots as well as shoots of the rice seedlings during a 5–20 days growth period. The activities of the enzymes of
starch hydrolysis α-amylase, β-amylase and starch phosphorylase declined in Al-exposed seedlings, whereas the activities of
sucrose hydrolyzing enzymes sucrose synthase and acid invertase increased in the seedlings due to Al3+ treatment. The enzyme of sucrose synthesis, sucrose phosphate synthase showed decreased activity in Al3+ treated seedlings compared to controls. Results suggest that Al3+ toxicity in rice seedlings impairs the metabolism of starch and sugars and favours the accumulation of hexoses by enhancing
the activities of sucrose hydrolyzing enzymes. 相似文献
6.
Arsenic (As) is a potential contaminant of groundwater as well as soil in many parts of the world. The effects of increasing
concentration of As (25 μm and 50 μm As2O3) in the medium on the content of starch and sugars and activity levels of enzymes involved in starch and sugar metabolism
i.e. α-amylase, β-amylase, starch phosphorylase and acid invertase were studied in germinating seeds of two rice cvs. Malviya-36 and Pant-12 during 0–120 h period. As toxicity in situ led to a marked decline in the activities of α-amylase, β-amylase in endosperms as well as embryoaxes of germinating rice
seeds. The activity of acid invertase increased in endosperms as well as embryoaxes whereas starch phosphorylase activity
declined in endosperms but increased in embryoaxes under As treatment. In endosperms a decline in starch mobilization was
observed under As toxicity, however under similar conditions the content of total soluble sugars increased in embryoaxes.
The observed inhibition in activities of amylolytic enzymes might contribute to delayed mobilization of endospermic starch
which could affect germination of seeds in As polluted environment, while the induced acid invertase activity and increased
sugar accumulation in embryoaxes could serve as a possible component for adaptation mechanism of rice seedlings grown under
As containing medium. 相似文献
7.
In order to better understand the various pathways of sucrose and starch catabolism in the anther of lily (Lilium hybrida var. “Enchantment”), invertase (EC 3.2.1.26) and amylase (EC 3.2.1.1, EC 3.2.1.2) activities were measured separately in
different fractions (anther wall, locular fluid and microspore/pollen) and correlated with the sugar content during anther
development. Our findings showed significant differences among the fractions analyzed, suggesting that the regulation of sucrose
and starch catabolism could follow distinct pathways in each fraction. Glucose and fructose amounts progressively decreased
from anther wall to fluid and from fluid to microspore/pollen. Thus, the developing pollen could act as a sink for the carbohydrates
that reach the anther. In this sense, cell wall-bound invertases seem to play a major role in soluble sugar partitioning in
the different fractions of the anther. Sucrose concentration was found to be substantially higher in the locular fluid than
in the other fractions, indicating a probable site for storage. On the other hand, the anther wall tissues could have a buffering
function, storing nutrient surplus in starch grains and thus regulating the availability of soluble sugars in the whole anther.
All these results proved the advantages of the experimental model proposed here, as well as its usefulness to investigate
sugar metabolism in Lilium anthers. 相似文献
8.
The effect of Zn nutrition on leaf starch metabolism was studied in two navy bean (Phaseolus vulgaris L.) varieties, Sanilac and Saginaw. Sanilac is much more susceptible to Zn deficiency than is Saginaw. The variables examined in these two strains were starch content, the activity of soluble starch synthetase (ADP-glucose: starch α-4-glucosyltransferase, EC 2.4.1.b), and the size and number of starch grains. All of these variables decreased during Zn deficiency. The reductions were much greater in Sanilac than in Saginaw. Thus, positive correlations exist between the relative changes in these variables in Sanilac and Saginaw under low Zn and their genotypic difference in growth response to low Zn. These results are taken to purport that the above observations most likely represent characteristic responses to Zn deficiency. We therefore suggest that, as a possible role in plant metabolism, Zn is involved in starch formation. 相似文献
9.
The levels of starch, soluble sugars, starch mobilizing enzymes(amylases and phosphorylase) and sodium [2-I4C] acetate incorporationinto essential oil have been examined during leaf ontogeny oflemongrass (Cymbopogon flexuosus Stapf., cv. OD-19). The degradationof starch was predominantly amylolytic and ß-amylasewas the major enzyme involved. Its activity was quite high duringthe period of active leaf growth accompanying active accumulationof essential oil. The activities of a-amylase and phosphorylasewere relatively lower. The change in starch to soluble sugarsratio was inversely related to ß-amylase activity.The time-course (12 h light followed by 12 h dark) monitoringof the [I4C]-radioactivity in starch and essential oil, afterexposure of the immature (15 days after emergence) leaf to 14CO2,revealed a progressive loss of label from starch and a parallelincrease in radioactivity in essential oil. The results havebeen discussed in relation to degradation of transitory starchserving as the source of carbon precursor for essential oil(monoterpene) biogenesis in the tissue. The amount of exogenouslysupplied acetate incorporated into essential oil increased tremendouslywith 5-10 fold decrease in specific activity of the labelledacetate (2,110 GBq mole1). The effect was largely manifestedin citral, the chief (ca. 80%) constituent oflemongrass essential oil. Ontogenetically, the amount of essentialoil synthesized from the exogenously supplied precursor (acetate)was much higher in young (10 days after emergence) than in mature(30 days after emergence) leaf. Thus, the leaf developmentalphase influences the expression of essential oil metabolismand actual synthesis. Only young lemongrass leaves are substantiallyactive to synthesize essential oil. The oil biosynthetic phaseappears to be coordinated/integrated with the development ofelevated levels of certain primary metabolic activities likestarch mobilization.
1CIMAP Publication No. 706
2Present address: CSIR Complex, Palampur-176 061, Kangra Distt.Himachal Pradesh, India
J Present address (until October 10, 1991): Department of Biology,Queen's University, Kingston, Ontario, K7L 3N6, Canada (Received November 30, 1990; Accepted May 31, 1991) 相似文献
10.
11.
Nisha Jain Kamal Dhawan Sarla P Malhotra Saleem Siddiqui Randhir Singh 《Acta Physiologiae Plantarum》2001,23(3):357-362
Changes in chemical composition and hydrolytic enzyme activities in guava fruits cv. Lucknow-49 have been reported at four
different stages of maturity, viz., mature green (MG), color turning (CT), ripe (R) and over ripe (OR). Chlorophyll content decreased, while carotenoid content
increased with advancement of ripening. Starch content decreased with concomitant increase in alcohol soluble sugars. The
cell wall constituents viz., cellulose, hemicellulose, and lignin decreased up to R stage, while the pectin content decreased throughout up to OR stage.
Among the cell wall hydrolyzing enzymes, polygalacturonase (PG) and cellulase exhibited progressive increase in activity throughout
ripening, while pectin methyl esterase (PME) activity increased up to CT stage and then decreased up to OR stage. The maximum
increase in the activities of cell wall hydrolysing enzymes was observed between MG and CT stages. The activities of starch
hydrolyzing enzymes, α-amylase and β-amylase decreased significantly with advancement of ripening. These changes in the activities
of hydrolyzing enzymes could be considered good indicators of ripening in guava. 相似文献
12.
Kazimierz Zalewski Lesław Bernard Lahuta Marcin Horbowicz 《Acta Physiologiae Plantarum》2001,23(1):73-78
Carbohydrate analysis was made of yellow lupin seeds (cv. Juno) and triticale kernels (cv. Dagro), produced by plants exposed
to drought stress for 21 days after the initial flowering of the first node of lupin and initial earing of triticale. The
seeds of all experimental variants were harvest at full maturity, dried and stored in linen bags at 18–20 °C. Soluble carbohydrates
were extracted and analysed as described by Horbowicz and Obendorf (1994).
Gas chromatographic separation of carbohydrates showed that raffinose family oligosaccharides (RFO) were dominant in lupin
seeds. The other carbohydrates present were sucrose (10 %), cyclitols and galactosyl cyclitols (12–13 %). Soil drought resulted
in higher levels of verbascose, but decreased the quantities of the other carbohydrates in lupine seeds.
In triticale kernels, over 50 % of soluble sugars were composed of sucrose and maltose, while 17.7 % were raffinose and stachyose.
In response to drought the content of mono- and oligosaccharides declined. The decrease of soluble carbohydrates content in
seeds of lupin and triticale kernels has no effect on the seed germination and vigour. It is assumed that the changes in the
concentration of soluble sugars observed under drought may impair the storability of triticale kernels, but improve it for
lupine seeds. 相似文献
13.
Abscission of pepper flowers is enhanced under conditions oflow light and high temperature. Our study shows that pepperflowers accumulate assimilates, particularly in the ovary, duringthe day time, and accumulate starch, which is then metabolizedin the subsequent dark period. With the exception of the petals,the ovary contains the highest total amounts of sugars and starch,compared with other flower parts and contains the highest totalactivity, as well as activity calculated on fresh mass basis,of sucrose synthase, in accordance with the role of this enzymein starch biosynthesis. Low light intensity or leaf removaldecreased sugar accumulation in the flower and subsequentlycaused flower abscission. The threshold of light intensity fordaily sugar accumulation in the sink leaves was much lower thanin flowers, resulting in higher daytime accumulation of sugarsin the sink leaves than in the adjacent flower buds under anylight intensity, suggesting a competition for assimilates betweenthese organs. Flowers of bell pepper cv. Maorand 899 (sensitive to abscission) accumulatedless soluble sugars and starch under shade than the flowersof bell pepper cv. Mazurka and of paprika cv.Lehava (less sensitive). The results suggest thatthe flower capacity to accumulate sugars and starch during theday is an important factor in determining flower retention andfruit set. Pepper; Capsicum annuum L.; abscission; shading; pepper flowers; ovary; leaves; sugars; starch; acid invertase; sucrose synthase 相似文献
14.
Summary Dicalcium phosphate dihydrate and potassium dihydrogen phosphate were applied to calcareous soil in combination with zinc
sulphate in the molar ratio of 100∶0, 100∶1, 100∶2 and 100∶4. Increasing addition of zinc sulphate into P sources gradually
increased KCl (0.01M) soluble P and Zn, NaHCO3 (0.5M, pH 8.5) extractable P and DTPA extractable Zn from soil and grain and straw yields of green gram. 相似文献
15.
Change in susceptibility of satsuma mandarin fruit (Citrus unshiu) cultivar “Miyagawawase” to sour rot pathogen was studied with relation to biochemical changes during maturation and storage.
The susceptibility of the fruit decreased with the advancement of maturity and was relatively constant during storage at 25°C
for 4 wk. The young, green fruit that contained less total soluble solid, sugars and polyphenol, but more citric acid and
water contents than mature, yellow fruit was more susceptible to sour rot pathogen. The susceptibility was correlated with
total soluble solid, citric acid, sugars and water contents, but not with polyphenol. The results suggested that the difference
in susceptibility during maturation was influenced to some extent by several constituents of fruit, although they may not
be the only factors involved in susceptibility. 相似文献
16.
The CO2 fixation rate of salt-stressed maize leaves was influenced by the Ca∶Na ratio in the solution cultures. At an osmotic potential
of −0.4 MPa in the root media, both the photosynthetic rate and the water-use efficiency declined as substrate Ca increased.
Blade-Ca concentration also increased, while blade-Na and-Mg decreased. Apparently photosynthetic activity was inhibited in
part by internal Mg deficiency rather than by Na toxicity or by Na-induced Ca deficiency. Reduction of the Ca∶Mg ratio in
the culture stimulated the CO2 fixation rate. 相似文献
17.
Enzymes of sucrose and hexose metabolism in developing kernels of two inbreds of maize 总被引:42,自引:6,他引:36 下载免费PDF全文
Tissue distribution and activity of enzymes involved in sucrose and hexose metabolism were examined in kernels of two inbreds of maize (Zea mays L.) at progressive stages of development. Levels of sugars and starch were also quantitated throughout development. Enzyme activities studied were: ATP-linked fructokinase, UTP-linked fructokinase, ATP-linked glucokinase, sucrose synthase, UDP-Glc pyrophosphorylase, UDP-Glc dehydrogenase, PPi-linked phosphofructokinase, ATP-linked phosphofructokinase, NAD-dependent sorbitol dehydrogenase, NADP-dependent 6-P-gluconate dehydrogenase, NADP-dependent Glc-6-P dehydrogenase, aldolase, phosphoglucoisomerase, and phosphoglucomutase. Distribution of invertase activity was examined histochemically. Hexokinase and ATP-linked phosphofructokinase activities were the lowest among these enzymes and it is likely that these enzymes may regulate the utilization of sucrose in developing maize kernels. Most of the hexokinase activity was found in the endosperm, but the embryo had high activity on a dry weight basis. The endosperm, which stores primarily starch, contained high PPi-linked phosphofructokinase and low ATP-linked phosphofructokinase activities, whereas the embryo, which stores primarily lipids, had much higher ATP-linked phosphofructokinase activity than did the endosperm. It is suggested that PPi required by UDP-Glc pyrophosphorylase and PPi-linked phosphofructokinase in the endosperm may be supplied by starch synthesis. Sorbitol dehydrogenase activity was largely restricted to the endosperm, whereas 6-P-gluconate and Glc-6-P dehydrogenase activities were highest in the base and pericarp. A possible metabolic pathway by which sucrose is converted into starch is proposed. 相似文献
18.
Polypeptides of the Maize Amyloplast Stroma
: Stromal Localization of Starch-Biosynthetic Enzymes and
Identification of an 81-Kilodalton Amyloplast Stromal Heat-Shock
Cognate 下载免费PDF全文
In the developing endosperm of monocotyledonous plants, starch granules are synthesized and deposited within the amyloplast. A soluble stromal fraction was isolated from amyloplasts of immature maize (Zea mays L.) endosperm and analyzed for enzyme activities and polypeptide content. Specific activities of starch synthase and starch-branching enzyme (SBE), but not the cytosolic marker alcohol dehydrogenase, were strongly enhanced in soluble amyloplast stromal fractions relative to soluble extracts obtained from homogenized kernels or endosperms. Immunoblot analysis demonstrated that starch synthase I, SBEIIb, and sugary1, the putative starch-debranching enzyme, were each highly enriched in the amyloplast stroma, providing direct evidence for the localization of starch-biosynthetic enzymes within this compartment. Analysis of maize mutants shows the deficiency of the 85-kD SBEIIb polypeptide in the stroma of amylose extender cultivars and that the dull mutant lacks a >220-kD stromal polypeptide. The stromal fraction is distinguished by differential enrichment of a characteristic group of previously undocumented polypeptides. N-terminal sequence analysis revealed that an abundant 81-kD stromal polypeptide is a member of the Hsp70 family of stress-related proteins. Moreover, the 81-kD stromal polypeptide is strongly recognized by antibodies specific for an Hsp70 of the chloroplast stroma. These findings are discussed in light of implications for the correct folding and assembly of soluble, partially soluble, and granule-bound starch-biosynthetic enzymes during import into the amyloplast. 相似文献
19.
W. E. Donaldson 《Biological trace element research》1993,36(3):319-326
Three experiments were conducted with day-old broiler chicks reared to 18 or 19 d of age. The objective was to examine the
effects of dietary oil (cottonseed oil vs fish oil), dietary antioxidant (0 vs 75 ppm ethoxyquin), and dietary lead (0 vs
1000 ppm Pb as lead acetate trihydrate) on hepatic fatty acid composition. A 2×2 factorial arrangement was used in all experiments.
In Experiment 1, the factors were oil (4% of each) and Pb. In Experiments 2 and 3, the factors were ethoxyquin and Pb in diets
containing 3.5% cottonseed oil (Experiment 2) or 3.5% fish oil (Experiment 3). Hepatic fatty acid profiles were measured by
gas-liquid chromatography in 10 chicks/treatment (Experiment 1) or 4 chicks/treatment (Experiments 2 and 3). Dietary oils
altered the profiles, with cottonseed oil producing the higher values for linoleic acid (18∶2) and arachidonic acid (20∶4).
With fish oil, in addition to the lower levels of 18∶2 and 20∶4, there were significant levels of eicosapentaenoic acid (20∶5)
and docosahexaenoic acid (22∶6). Pb enhanced the levels of 20∶4, but the effect was greater with cottonseed oil diets compared
with fish oil diets. The enhanced 20∶4 levels resulted in lower ratios of 18∶2/20∶4. Ethoxyquin enhanced the level of 18∶2
with the cottonseed oil diet, and of 20∶5 and 22∶6 with the fish oil diet. Ethoxyquin decreased the level of hepatic 20∶4
when fish oil was fed. The results clearly show that all three factors (oil type, Pb level, and ethoxyquin level) after hepatic
fatty acid composition. Both oil source and Pb level appeared to exert an effect on the metabolic conversion of 18∶2 and 20∶4.
The primary effect of ethoxyquin was to enhance the levels of polyunsaturated fatty acids in liver. The data do not allow
the partitioning of possible ethoxyquin effects to protection of polyunsaturated acids in feed vs protection of polyunsaturated
acids in liver tissue.
Use of trade names implies neither approval by the North Carolina Agricultural Research Service of products named nor criticism
of products not named. 相似文献
20.
Grange, R. 1. 1985. Carbon partitioning in mature leaves ofpepper: effects of daylength.J. exp. Bot. 36: 17491759. The partitioning of recently fixed carbon has been examinedin mature pepper leaves grown in 6, 10 or 14 h photoperiodsat different irradiances chosen to give similar radiation integralsand in a 6 h photoperiod at the lowest of these irradiances.The partitioning of carbon into export, starch, sugars and respirationwas followed over the photopenod and the subsequent night ina mature leaf. The maximum export rate during the day (approximately 18 µgC cm2 leaf h1) was not significantly differentamong the treatments. Net photosynthesis rate was directly relatedto irradiance; the proportion of net photosynthesis exportedduring the day was 33% in 6-h days and 57% in 14-h days. Leafstarch accumulation (as a proportion of net photosynthesis rate)increased slightly when plants were grown in 6-h days. The remobilization of starch and sugars at night allowed exportrates to remain similar over 24 h when plants were grown in10-h or 14-h photoperiods. Leaves grown in 6-h days showed nosignificant changes in export rate during the first few hoursof night but exhausted their starch reserves during the nightand export rates declined. Sucrose and hexose levels decreased at the onset of darkness,but did not fall below 40 µg cm2 in plants grownin 10-h or 14-h photoperiods; when this level was reached after34 h of darkness, starch breakdown began. In leaves grownin both 6-h treatments, sucrose levels fell below 40 µgcm2 when starch reserves were depleted during the nightand the export rate decreased concurrently. The results are discussed in relation to the control of exportand starch metabolism in the leaf. Key words: Pepper, partitioning, daylength 相似文献