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1.
Welbaum Gregory E.; Muthui Wangechi J.; Wilson James H.; Grayson Randolph L.; Fell Richard D. 《Journal of experimental botany》1995,46(4):391-400
Muskmelon (Cucumis melo L.) embryos are enclosed in an envelopeof tissue consisting of a layer of endosperm and a multi-cell-layeredperisperm that the radicle must penetrate for germination tooccur. The force and energy required to penetrate the perispermenvelope tissue were measured using an Instron universal testingmachine at a crosshead speed of 5 mm min1 after 0, 10,15, 22, 23, and 25 h of imbibition at 25C. The cellular structureof perisperm envelope tissue surrounding the radicle was observedafter 10, 15, 20, 25, and 48 h of imbibition using scanningelectron microscopy. The force required to puncture 5-mm-long,micropylar seed pieces declined steadily from 1.65 N in driedseeds to 0.65 N after 21 h of imbibition. The penetration energydeclined from 3.0 N mm in dry seeds to 1.1 N mm at 21 h afterthe start of imbibition when the first seeds germinated. Theforce and energy required to penetrate germinated seed pieceswere 0.55 N and 0.9 N mm, respectively, so the net punctureforce and energy needed to rupture the micropylar region ofthe perisperm envelope was roughly 0.10 N and 0.2 N mm at radicleemergence, respectively. Instron measurements of penetrationforce and energy decreased dramatically at crosshead speedsless than the 5 mm min1. Crosshead speeds greater than5 mm min1 may overestimate the pressure needed to ruptureperisperm and endosperm tissues. Intracellular cracks were firstobserved in SEM images 15 h after the start of imbibition, andafter 20 h cracking was apparent throughout the micropylar regionof the perisperm envelope. The perisperm envelope ruptured inone of two ways, coincident with radicle emergence. In approximately85% of muskmelon seeds, a large crack formed in the perispermenvelope adjacent to the radicle, while in roughly 15 % a circulararea of the perisperm envelope detached during radicle emergence.In dead seeds, the penetration force remained constant from1024 h after the start of imbibition, and there wereno visible signs of tissue degradation. Cellular degradationand weakening of the perisperm envelope tissue precedes radicleemergence in muskmelon seeds. Key words: Seed, Instron, turgor, cell wall, electron microscopy, Cucumis melo 相似文献
2.
Flow cytometric determination of cell cycle activation duringimbibition and visible germination in five families of jackpine (Pinus banksiana Lamb.) embryos and megagametophytes revealedthat in seeds that had undergone no imbibition the majorityof cells were in the 2C state. As the imbibition period increased,less of the nuclei were blocked in the G0/G1 state and morebecome active in the cell cycle. The augmentation in the nucleiactive in the 2C4C cycle as well as those with DNA levelshigher than the 4C state occured gradually and preceeded radicleemergence. In megagametophyte tissue examined at various stagesof imbibition, cell cycle activity became apparent rapidly followingimbibition. In nuclei of green and white embryos examined separatelythe 2frequency distributions were significantly different forall three families after 144h. As imbibition period increased,fewer nuclei from the green embryos were blocked in the 2C state,and more became active in the 2C4C cell cycle. This wasnot the case for white embryos where no significant linear relationwas noted. Cell cycle activity in the hypocotyl+cotyledons regionand the emerging radicle were examined separately. Functionalrelations found in the hypocotyl+cotyledons region were notevident in the radicle. As visible germination proceeded, cellcycle activity in the hypocotyl + cotyledons region for thisperiod of germination showed a reversal of the activity notedduring imbibition: fewer nuclei were active and once again ahigher proportion were found in the 2C state. cell cycle; C levels; DNA content; flow cytometry; germination; imbibition; jack pine; megagametophyte; Pinus banksiana Lamb 相似文献
3.
The Use of Abscisic Acid to Synchronize Carrot Seed Germination Prior to Fluid Drilling 总被引:1,自引:0,他引:1
Abscisic acid (ABA) was used as a reversible block to the progressof carrot seed germination in a practical seed treatment. Pre-treatingseeds with 104M ABA solution at 15 °C for 12 d gave93% germination of viable seeds on subsequent transfer to waterbefore radicle lengths became too long for fluid drilling. Thiscompared with only 31 % without pre-treatment ABA pretreatment significantly increased the synchrony of carrotseed germination and did not affect final percentage germinationor early seedling growth rates. Seedling emergence from ABA-treatedgerminating seeds was earlier and more uniform than from untreatedgerminating seeds and seedlings from both these treatments emergedbefore those from ungerminated seeds Daucus carota L., carrot, germination, seed treatment, fluid drilling, abscisic acid, radicle extension 相似文献
4.
KERMODE ALLISON R.; DUMBROFF E. B.; BEWLEY J. DEREK 《Journal of experimental botany》1989,40(2):303-313
During mid-development (2540 d after pollination: DAP)of the castor bean seed the amount of abscisic acid (ABA) increasesin both the endosperm and the embryo, declining substantiallythereafter until there is little present in the mature dry (60DAP) seed. Premature desiccation of the seed at 35 DAP alsoleads to a major decline in ABA within the embryo and endosperm.Partial water loss from the seed at 35 DAP which, like naturaland premature desiccation, leads to subsequent germination uponreturn of the seed to full hydration, causes a much smallerdecline in ABA levels. In contrast, ABA declines substantiallyin the non-dried (hydrated) control at 35 DAP, but the seedsdo not germinate. Hence, a clear negative correlation betweenABA content and germinability is not observed. Both drying,whether natural or imposed prematurely, and partial drying decreasethe sensitivity of the isolated embryo to exogenous ABA by about10-fold. The protein synthetic response of the castor bean embryo exposedto 0.1 mol m3 ABA following premature desiccation exhibitssome similarity to the response of the non-dried developingembryoin both cases the synthesis of some developmentalproteins is enhanced by ABA, and germination is suppressed.Germination of mature seeds is also suppressed by 0.1 mol m3ABA, but the same developmental proteins are not synthesized.In the cotyledons of prematurely-desiccated seed, some proteinsare hydrolysed upon imbibition in 0.1 mol m3 ABA, a phenomenonthat occurs also in the cotyledons of similarly treated matureembryos, but not in developing non-dried embryos. Hence theembryo exhibits an intermediate response uponrehydration in 0.1 mol m3 ABA following premature desiccation;viz. some of the responses are developmental and some germinative.Following natural or imposed drying, the isolated embryo becomesrelatively insensitive to 0.01 mol m3 ABA: germinationis elicited and post-germinative reserve breakdown occurs inthe radicle and cotyledons. The reduced sensitivity of the embryoto ABA as a consequence of desiccation may be an important factorin eliciting the switch to germination and growth within thewhole seed. Key words: Abscisic acid, desiccation, astor bean endosperm, seed development, germination, protein synthesis, isolated embryos, hormone sensitivity 相似文献
5.
6.
Moisture Loss as a Prerequisite for Seedling Growth in Soybean Seeds (Glycine max L. Merr.) 总被引:1,自引:0,他引:1
Rosenberg, L. A. and Rinne, R. W. 1986. Moisture loss as a prerequisitefor seedling growth in soybeanseeds (Glycine max L. Merr.).J.exp. Bot. 37: 16631674. As soybean seeds [Glycine max (L.) Merr.] develop, they undergoa change in seed moisture. When excised prematurely from thepod and planted, seeds do not exhibit seedling growth until63 d after flowering (DAF) when the seed moisture has fallenbelow 60%. In contrast, seed germination (radicle protrusion)can occur when seeds as young as 35 DAF (6879% moisture)are excised, but this germination docs not lead to comparableseedling growth frequencies unless seeds are first given a moistureloss treatment to artificially reduce their moisture below 60%.A moisture loss treatment applied at 35 DAF thus enables seedto undergo the transition from germination (cell expansion)to seedling growth (cell division and expansion) to the extentthat treated immature seed have a vigour index comparable toseeds matured on the plant (100%). The pattern of protein synthesisin vivo was examined in 35 DAF seed using [35S]-methionine incorporation.When moisture loss treatment was applied for 24 h to 35 DAFseeds, seeds synthesized several new polypeptides when comparedwith untreated seeds at the same developmental stage. The sameseed samples showed 0% seedling growth in the absence of moistureloss treatment and 80% seedling growth when the treatment hadbeen applied. Moisture loss from soybean seeds appears to bea prerequisite for the synthesis of new proteins which may bepart of the metabolic process or processes that allow the soybeanseed to undergo the transition from seed germination to seedlinggrowth. Key words: Moisture loss, germination/growth, soybean 相似文献
7.
Seed Germination and Radicle Growth of a Halophyte, Kalidium caspicum(Chenopodiaceae) 总被引:9,自引:0,他引:9
Effects of temperature, light, NaCl and polyethylene glycol(PEG)-6000 on seed germination and radicle growth in a halophyticshrub, Kalidium caspicum(L.) Ung.-Sternb. were investigated.When seeds were incubated in deionized water at constant temperaturesbetween 10 and 30°C, the percentage germination in the darkexceeded 75%; light suppressed seed germination at alternatingtemperatures. Incubating seeds with a hypersaline solution ofNaCl for 30 d had no adverse effect on their germinability.The percentage germination of seeds incubated with a 0.8MPa NaCl solution was 73, 80 and 54% at 10, 20 and 30°C,respectively, but all radicles died before their length exceeded5 mm. In contrast, when seeds were incubated with a 0.8MPa PEG solution at 20°C, 68% of seeds germinated, and 95%of the emerging radicles survived beyond 5 mm. The high sensitivityof small radicles of this species to salinity indicated thatsalt must be removed from the soil surface for seedling establishment.Copyright2000 Annals of Botany Company Chinese desert, radicle growth, germination, halophyte, Kalidium caspicum, salinity 相似文献
8.
Soybean seeds [Glycine max (L.) Merr.] synthesize de novo andaccumulate several non-storage, soluble polypeptides duringnatural and precocious seed maturation. These polypeptides havepreviously been coined maturation polypeptides.The objective of this study was to determine the fate of maturationpolypeptides in naturally and precociously matured soybean seedsduring rehydration, germination, and seedling growth. Developingsoybean seeds harvested 35 d after flowering (mid-development)were precociously matured through controlled dehydration, whereasnaturally matured soybean seeds were harvested directly fromthe plant. Seeds were rehydrated with water for various timesbetween 5 and 120 h. Total soluble proteins and proteins radio-labelledin vivo were extracted from the cotyledons and embryonic axesof precociously and naturally matured and rehydrated seed tissuesand analyzed by one-dimensional PAGE and fluorography. The resultsindicated that three of the maturation polypeptides (21, 31and 128 kDa) that had accumulated in the maturing seeds (maturationpolypeptides) continued to be synthesized during early stagesof seed rehydration and germination (530 h after imbibition).However, the progression from seed germination into seedlinggrowth (between 30 and 72 h after imbibition) was marked bythe cessation of synthesis of the maturation polypeptides followedby the hydrolysis of storage polypeptides that had been synthesizedand accumulated during seed development. This implied a drasticredirection in seed metabolism for the precociously maturedseeds as these seeds, if not matured early, would have continuedto synthesize storage protein reserves. Glycine max (L.) Merr, soybean, cotyledons, maturation, germination/seedling growth 相似文献
9.
Effects of chilling (5 °C) period, light and applied nitrogen(N) on germination (%), rate of germination (d to 50% of totalgermination; T50%) and seed imbibition were examined inClematisvitalba L. In the absence of chilling, light and N, germinationwas minimal (3%). When applied alone, both chilling and N increasedgermination. Chilling for 12 weeks increased germination to64%, and 2.5 mM NO-3or NH+4increased germination to 1012%.Light did not increase germination when applied alone, but didwhen applied in combination with chilling and/or N. Half theseed germinated when light was combined with 2.5 mM NO-3or NH+4.The influence of chilling, light and/or N on germination wasgreater when combined, than when either factor was applied alone.Both oxidized (NO-3) and reduced (NH+4) forms of N increasedgermination, but non-N-containing compounds did not, suggestingthe response was due to N and not ionic or osmotic effects. Without additional N, T50%decreased from 1620 d at zerochilling, to around 5 d at 8 and 12 weeks chilling. AlthoughT50%was not influenced by an increase in NO-3or NH+4from 0.5to 5.0 mM , it did increase with additional applied N thereafter.However, the magnitude of the N effect was small compared tothat of chilling. Like germination, seed imbibition increasedwith a longer chilling period, but in contrast imbibition decreasedslightly with increased applied NO-3or NH+4. It is argued thatincreased imbibition is not directly related to an increasein total germination, but that it may be related to the rateof germination. Possible mechanisms involved in the reductionin dormancy ofC. vitalba seed are discussed. Clematis vitalba L.; germination; dormancy; imbibition; rate of germination; chilling; light; nitrate; ammonium; nitrogen; phytochrome 相似文献
10.
Effects of Temperature and Water Potential on Germination, Radicle Elongation and Emergence of Mungbean 总被引:2,自引:1,他引:1
Controlled environment experiments were performed to determinethe effects of temperature and water potential on germination,radicle elongation and emergence of mungbean (Vigna radiata(L.) Wilczek cv. IPB-M79-17-79). The effects of a range of constant temperatures (1545°C) and water potentials (0 to 2.2 MPa) on germinationand radicle elongation rates were studied using an osmoticumtechnique, in which seeds were held against a semi-permeablemembrane sac containing a polyethylene glycol solution. Linearrelationships were established between median germination time(Gt50) and water potential at different temperatures, and betweenreciprocal Gt50 (germination rate) and temperature at differentwater potentials. Germination occurred at potentials as lowas 2.2 MPa at favourable temperatures (3040 °C),but was fastest at 40 °C when water was not limiting, withan estimated base temperature (Tb) of about 10 °C. Subsequentradicle elongation, however, was restricted to a slightly narrowertemperature range and was fastest at 35 °C. The conceptof thermal time was used to develop an equation to model thecombined effects of water potential and temperature on germination.Predictions made using this model were compared with the actualgermination obtained in a related series of experiments in columnsof soil. Some differences observed suggested the additionalimportance of the seed/soil/water contact zone in influencingseed germination in soil. Seedling emergence appeared to reflectfurther the radicle elongation results by occurring within anarrower range of temperatures and water potentials than germination.Emergence had an estimated Tb of 12.6 °C and was fastestat 35 °C. A soil matric potential of not less than about0.5 MPa at sowing was required to obtain 50% or moreseedling emergence. Key words: Germination, temperature, water potential 相似文献
11.
LIU YONGQING; HILHORST HENK W. M.; GROOT STEVEN P. C.; BINO RAOUL J. 《Annals of botany》1997,79(2):161-168
Using X-ray photography and flow cytometry, the internal morphologyand DNA replication activity of wild type (wt), GA- (gib-1 )and ABA-deficient (sitw ) tomato (Lycopersicon esculentum Mill.cv. Moneymaker) mutant seeds were studied. During seed formation,from 30 to 45 d after pollination (DAP) the endosperm becomessolid and the seed starts to gain desiccation tolerance. Atthis time significant changes occur in the amounts of DNA inradicle tip cells. At 30 DAP, radicle tip cells of the threegenotypes manifest about 60% of 2C, 30% of 4C and 10% of 8Camounts of DNA. Upon maturation (45 DAP onwards), most cellsin the seeds of the three genotypes arrest in the G1phase ofthe cell-cycle with 2C amounts of DNA. However, a relativelyhigh proportion of cells with 4C amounts of DNA was detectedin the radicle tip cells ofsitw compared with wild type andgib-1. At the well-matured stage (60 DAP), there were about 2% ofseeds with free space in wild type andgib-1 , and about 13%insitw . At the over-matured stage (75 DAP), even more seedswith free space were found insitw , whereas no increase in theproportion of the seeds with free space was detected in theother two genotypes. In -1.0 MPa PEG-6000 with or without 10µM GA4+7, no germination occurred in well-matured wildtype andgib-1 seeds, whether or not they were dried after harvest.However,sitw seeds were able to germinate both in over-maturefruit and in -1.0 MPa PEG-6000. Priming of dried seeds in -1.0MPa PEG induced a large amount of free space in almost all seedsof the three genotypes, and nuclear DNA synthesis in the radicletip cells of wild type andsitw seeds. However, PEG priming offresh (non-dried) seeds had no effect on the amount of freespace and 2C/4C DNA ratios in wild type orgib-1 seeds, but didinduce free space in about 2025% ofsitw seeds and provoked4C signals insitw seeds. Removal of the endosperm and testaopposite the radicle tip of seeds resulted in root protrusion,the induction of free space and an increase of 4C DNA signalsin the three genotypes. It is concluded that ABA is crucialfor the efficient arrest of tomato embryo radicle tip cellsin G1phase upon maturation, whereas GAs play an important rolein re-initiating 4C DNA levels upon germination. Dormancy; flow cytometry; free space; Lycopersicon esculentum ; maturation; priming; seed; tomato 相似文献
12.
A linear relationship between constant temperatures in the sub-optimaltemperature range and germination rate is shown in both Quercusrobur L and Castanea sativa Mill germinated under nominal darkconditions. The mean base temperature was interpolated for Qrobur as 0 8 ? or 2-4 ?, depending on seed lot provenance, andfor C. sativa as 1 -4? The optimum temperature for germinationin Q. robur was about 20? compared with around 28 ? in C. sativaOver the sub-optimal temperature range the distribution of thermaltimes was log-normal for each population studied their spreadvarying both between Q robur seed lots and between species However,in C. sativa germinated close to the mean base temperature,the distribution in thermal times was reduced Thermal timesto germination were decreased in Q. robur and C sativa by approximately0 3 and 0-5 log-units, respectively, when the pericarp was removed,i.e in the seeds, but the sensitivity of the response remainedrelatively unaltered In both species the germination rate was the same when nominaldark or safe green light conditions were employed during thegermination test. However, at 21 ? Q robur exhibited the highirradiance reaction (HIR) at photon doses above 30mmol m2d1. HIR first affected the germination rate by an inhibitionof radicle extension The sensitivity of the response to thermaltime was reduced as photon dose increased. This photo-inhibitionwas exacerbated at supra-optimal temperatures. In contrast,C. sativa germination rate at 26 ? was little influenced bylight at a photon dose of 752 mmol m2 d1 Key words: Seed germination rate, temperature, thermal time, light, photon dose 相似文献
13.
Seeds of Hancornia speciosa germinated best at a temperatureof 2030 °C. The viability of the seeds during storagewas short and the best storage conditions for viability entailedkeeping the seeds in polyethylene bags. Seed viability was maintainedonly when the seeds were stored at a moisture content above30%; storage conditions which allowed dehydration resulted ina rapid loss of viability (the seeds showed recalcitrant behaviour). Low temperature during storage did not improve longevity. Arelationship between germination and moisture content was established,but when the moisture content fell below 25% there was a drasticreduction of germination. After 9 weeks of storage, even athigh moisture content, seeds lost viability. Loss of seed viability during seed dehydration was associatedwith increased leakage of electrolytes and organic solutes,and reduced tetrazolium staining during subsequent imbibition. Hancornia speciosa, germination, recalcitrant seeds, storage, moisture 相似文献
14.
Priming and accelerated ageing affect L-isoaspartyl methyltransferase activity in tomato (Lycopersicon esculentum Mill.) seed 总被引:1,自引:0,他引:1
Damage and degradation of cellular proteins is observed duringage-induced seed deterioration. L-Isoaspartyl protein methyltransferase(EC 2.1.1.77
[EC]
) is an enzyme hypothesized to play a role in limitingand repairing age-induced damage to proteins. Tomato (Lycopersiconesculentum Mill. New Yorker) seeds were assayedfor changes in L-isoaspartyl methyl-transferase activity duringaccelerated ageing and after osmotic priming. Accelerated ageingof seeds for 14 d at 45C and 100% relative humidityreduced germination from 94% to 71%, increased the mean timeof germination (MTG) from 2.4 to 5.8 d, and was accompaniedby a correlative decrease in L-isoaspartyl methyltransferaseactivity (r2=0.90). Aged and untreated seeds were primed for7 d at 20C in darkness using aerated solutions of 3% KNO3 orpolyethylene glycol 8000 (PEG) with equivalent osmotic potential(1.25 MPa). Priming with KNO3 decreased the MTG, butdid not improve germination percentage for untreated seeds.Priming did not affect L-isoaspartyl methyltransferase activityin untreated seeds, but restored activity in aged seeds primedin KNO3 to levels near that of untreated seeds. Priming withPEG did not effectively improve the MTG or increase L-isoaspartylmethyltransferase activity. During germination, L-isoaspartylmethyltransferase activity remained constant for 48 h post-imbibitionand then declined, suggesting that the enzyme was developmentallyregulated and inactivated or degraded as radicle emergence occurred. Key words: L-Isoaspartyl methyltransferase, protein repair, seed priming, accelerated ageing, Lycopersicon esculentum 相似文献
15.
Wheat (Triticum aestivum L.) embryos form in dynamically-regulatedovular environments. Our objectives were to improve developmentof cultured immature wheat embryos by simulating, in vitro,abscisic acid (ABA) levels and O2 tensions as found in wheatovules during zygotic embryogenesis. We characterized from intactwheat kernels embryo respiration, embryo morphology and embryoand endosperm + ABA levels at 13, 19 and 25 d post-anthesis(DPA). Young (13 DPA) embryos were then excised and culturedin vitro, where they were exposed to 0·2 or 2·Ommol m3 ±ABA and 2.·1, 2·5 or 7·4mol m3 (6, 7 and 21%, respectively) gaseous O2. At 6and 12 d in culture, + ABA levels, embryo respiration and embryomorphology were characterized by treatment. Thirteen-day-oldembryos from two different plant populations differed by 17-foldin initial ABA content. However, this difference did not affectprecocious germination in vitro, nor did it affect the amountof exogenous ABA required to reduce precocious germination by40%. In this respect, embryos from both populations were equallysensitive to exogenous ABA. Cavity sap O2 levels (2·1to 2·5 mol m3) were much more effective in preventingprecocious germination of cultured embryos than were cavitysap levels of ABA (0·2 to 2·0 mmol m3).The combination of physiological levels of both ABA and O2 largelynormalized DW accumulation and embryo morphology without alteringendogenous + ABA levels. Residual respiration of cultured embryoswas higher than that of embryos grown in situ, and was not influencedby the exogenous O2 and ABA treatments Key words: Abscisic acid, embryo development, oxygen tensions, respiration, wheat 相似文献
16.
Responses of Vegetable Seeds to Controlled Hydration 总被引:1,自引:1,他引:0
Leek, onion and carrot seeds were imbibed in water and in solutionsof polyethylene glycol (PEG) 6000 over the range 0.5to 4.0 MPa osmotic potential, for periods up to 28 dat 15 C. Seeds started to germinate after 7 and 14 d at 0.5MPa and 1.0 MPa PEG, respectively, but in the lattercase, germination did not exceed 5%. No germination occurredin solutions of lower (more negative) osmotic potential. Seedmoisture content increased with osmotic potential in all threespecies and the relationships were unaffected by the durationof imbibition in solutions of 1.0 to 4.0 MPa,though leek seeds had higher moisture contents than the otherspecies for any given osmotic potential. Linear relationships between response to priming (differencebetween mean germination times of primed and untreated seeds)and seed moisture content were obtained for each species, positiveresponses being obtained above 3035% seed moisture contentwith optima at 46, 44.5 and 44% seed moisture contents in leek,onion and carrot, respectively. Priming had no effect on embryovolume or cell number per embryo in leek and onion. Carrot embryovolume increased by 43% and cell number per embryo doubled inprimed compared with untreated seeds, whereas seeds imbibedin water showed only a slight increase in cell number per embryoat the stage when radicles were beginning to penetrate the seedcoat. Allium cepa L. cv. Rijnsburger Robusta, onion, Allium porrum L. cv. Winterreuzen, leek, Daucus carota L. cv. Nantaise, carrot, germination, priming, polyethylene glycol, seed moisture, cell number, embryo volume 相似文献
17.
Short-day photoperiods can increase the partitioning of assimilatesto filling seeds of soybean (Glycine max L. Merr.), resultingin higher seed growth rates. The plant growth substance ABAhas been implicated in the regulation of assimilate transferwithin filling soybean seeds. Thus, we hypothesized that anincreased concentration of endogenous ABA in seeds may enhancesucrose accumulation and seed growth rate of soybeans exposedto short-day photoperiods. Plants of cv. Hood 75 were grownin a greenhouse under an 8-h short-day photoperiod (SD) until11 d after anthesis (DAA) of the first flower, when half ofthe plants were transferred to a night-interruption (NI) treatment(3 h of low-intensity light inserted into the middle of thedark period). Plants remaining in SD throughout seed developmenthad seed growth rates 43% higher than that of plants shiftedto NI (7·6 mg seed1 d1 vs. 5·3 mgseed1 d1). On a tissue-water basis, the concentrationof ABA in SD seeds increased rapidly from 7.6 µmol l1at 11 DAA to 65·2 µmol l1 at 18 DAA, butthen declined to 6·6 µmol l1 by 39 DAA.In contrast, the concentration of ABA increased more slowlyin NI seeds, reaching only 47·4 µmol l1by 18 DAA, peaking at 57·0 µmol l1 on 25DAA, and declining to 10·2 µmol l1 by 39DAA. The concentration of sucrose in SD embryos peaked at 73·5mmol l1 on 25 DAA and remained relatively constant forthe remainder of the seed-filling period. In NI, the concentrationof sucrose reached only 38·3 mmol 11 by 25 DAA,and peaked at 61·5 µmol l1 on 32 DAA. Thusin both SD and NI, sucrose accumulated in embryos only afterthe peak in ABA concentration, suggesting that ABA may havestimulated sucrose movement to the seeds. The earlier accumulationof ABA and sucrose in SD suggests that ABA may have increasedassimilate availability during the critical cell-division period,thus regulating cotyledon cell number and subsequent seed growthrate for the remainder of the seed-filling period. Glycine max L. Merr. cv. Hood 75, soybean, assimilate partitioning, abscisic acid, photoperiod, source-sink 相似文献
18.
The response of the germination of seeds of Barbarea vema (Mill.)Aschers, Brassica chinensis L., Brassica juncea (L.) Czern.& Coss., Brassica oleracea L. var. gongylodes L., Camelinasaliva (L.) Crantz, Eruca saliva Mill., Lepidium sativum L.,Nasturtium officinale R. Br., and Rorippa palustris (L.) Besserto white fluorescent light of different photon flux densitiesapplied for different daily durations in a diurnal alternatingtemperature regime of 20 °C/30 °C (16 h/8 h) was quantifiedby linear relations between probit percentage germination andthe logarithm of photon dose, the product of photon flux densityand duration. The low energy reaction, in which increasing dosepromotes germination, was detected in all the seed populationsbut in Barbarea vema and Brassica Juncea the lowest photon doseapplied (1052 and 105 7 mol m2 d1,respectively) was sufficient to saturate the response. Comparisons,where possible, between photoperiods demonstrated reciprocity,i.e. germination was proportional to photon dose irrespectiveof photoperiod, for the low energy reaction in Brassica oleracea(1 min d1 to 1 h d1), Camelina saliva (1 min d1to 8 h d1), Eruca saliva (1 min d1 to 24 h d1),Lepidium sativum (I min d1 to 8 h d1) and Rorippapalustris (1 min d1 to 8 h d1), but not in Brassicachinensis and Nasturtium officinale. The high irradiance reaction,in which increasing dose inhibits germination, was detectedin Barbarea vema, Brassica chinensis, Brassica juncea, Brassicaoleracea, and Camelina saliva. The minimum dose at which inhibitionwas detected was lO03 mol m2 d1.These results are discussed in the context of devising optimallight regimes for laboratory tests intended to maximize germination The response of germination to photon dose was also quantifiedwith 3 x 104 M GA2, co-applied (Brassica chinensis, Camelinasaliva, and Lepidium sativum) and with 2 x 102 M potassiumnitrate co-applied (Brassica chinensis). In the latter casepotassium nitrate had no effect in the dark and inhibited germinationin the light, but GA2, promoted germination substantially inall three species. Variation amongst seeds in the minimum photondose required to stimulate germination was not affected by co-applicationof GA2, in Brassica chinensis and Camelina saliva, whereas seedsof Lepidium salivum showed a narrower distribution of sensitivitiesto the low energy reaction in the presence of GA2 Barbarea vema (Mill.) Aschers, Brassica chinensis L., Brassica juncea (L.) Czern. & Coss., Brassica oleracea L. var. gongylodes L., Camelina saliva (L.) Crantz, Eruca saliva Mill., Lepidium satiaum L., Nasturtium officinale R. Br., Rorippa palustris (L.) Besser, Cruciferae, light, gibberellic acid, seed germination, seed dormancy 相似文献
19.
Seeds of different vigour also differ in their germination ability.In rice (Oryza sativa), this difference was correlated withthe level of incorporation of 35S-methionine into 25-60% ammoniumsulphate precipitable material that was rich in amylase proteins.This protein fraction, from dry seeds, contained no -amylaseactivity. In contrast, ß-amylase activity was presentin all seed stocks capable of 99% germination, although thelevel was lower in seeds that grew slowly when germinated. Inlow viability low vigour stock (i.e. extensively deterioratedseeds) ß-amylase activity was absent. Alpha-amylaseactivity in all stocks was detected only after 24 h from thestart of imbibition. These results indicate that ß-amylaseactivity is reliable indicator of the germination ability ofrice seed stocks and of their vigour during germination.Copyright1995, 1999 Academic Press Rice (Oryza sativa L.,), germination, ß-amylase, -amylase, seed vigour 相似文献
20.
Abscisic Acid Content and Effects During Dehydration of Detached Leaves of Desiccation Tolerant Plants 总被引:2,自引:1,他引:1
Borya nitida is an angiospcrm whose detached leaves developcomplete tolerance to dehydration when they are equilibratedto air of 96% r.h. This treatment causes leaves to yellow aschlorophyll is destroyed, and abscisic acid contents increaseseveral-fold. Exogenous ABA (at 0.0380.38 mol m3)promoted desiccation tolerance (a) in leaves undergoing toleranceinduction at 96% r.h., (b) only slightly during rapid dryingat rates which are normally injurious, and (c) considerablyin turgid tissue treated with ABA 48 h before rapid drying. ABA content also increased with intense water stress in Myrothamnusflabellifolia, a desiccation tolerant angiosperm which, unlikeBorya, retains most of its chlorophyll when dehydrated. Preliminaryincubation in ABA of detached leaves of this resurrectionplant also promoted survival during rapid drying. Theability of ABA to substitute for the normal induction periodsuggests that this hormone participates in the development ofdesiccation tolerance. Key words: Abscisic acid, ABA, Drought tolerance, Resurrection plant 相似文献