The Effect of Accelerated Aging of Sorghum Seeds on Seedling Vigour

Six different levels of vigour of sorghum seeds from an identicallot were obtained through accelerated aging for various periodsof time. Vigour was estimated according to yielding abilityof the seed in the field. After 6 d of aging, seed invigoration,to the extent of a 20% increase in yield, was observed. However,this was followed by a gradual decrease in yield following agingof up to 48 d. All seed lots showed 88–92% germinationor emergence capacity when tested in the laboratory, which correlatespoorly with vigour. However, vigour correlated well with therates of germination and root emergence when tested in the laboratory,as well as with emergence rate in the field.     

The Effects of Priming and Ageing on Seed Vigour in Tomato

A comparison was made of the effects of seed priming or ageingtreatments on the performance of tomato (Lycopersicon esculentumMill. cv. UC204C) seeds according to a number of indices ofseed vigour. A single lot of tomato seeds was primed in 120mol m^–3 K2HPO4 + 150 mol m^–3 KNO₃ for 5 d at 20?C, or aged at 13% moisture content (dry weight basis) and 50?C for 6 d. Germination percentage (>98%) was unaffectedby priming and reduced to 85% by ageing. X-ray photographs andlongitudinal sections revealed the formation of free space surroundingthe embryo in dry primed seeds, which was not evident in controlor aged seeds. Priming increased the rate of germination atall temperatures above the base temperature (T_b), while ageingdecreased it. T_b was unaffected by priming and only slightlyincreased by ageing. The variation in individual times to germinationwas approximately doubled in both primed and aged seed comparedto the control, based upon the slopes of probit germinationpercentage versus log thermal time curves. Root growth aftergermination tests and seedling growth in both greenhouse andfield tests were not influenced by either priming or ageing.The conductivity test was found to be unreliable as a vigourtest for tomato seeds. The results identify several indiceswhich can be used to quantify seed vigour in tomato. They alsoillustrate that seed priming can enhance seed performance accordingto some criteria, while having no effect or decreasing qualityaccording to other criteria. Seed vigour can apparently be separatedinto various components which can be independently influencedby seed enhancement treatments. Key words: Tomato, seed germination rate, seed priming, seed vigour     

Invigoration of Cotton Seedlings by Treatment of Seeds for Pregermination Activities

Incubation of cotton seeds (Gossypium hirsutum, cv. Acala S.J.2) at 20 °C and 95% r.h. for up to 12 d results in an increasein seed water content and in a higher rate of seedling development.When seed vigour is measured by tolerance to high temperaturestorage (aging conditions) or tolerance to low temperature andsalinity during germination, seeds incubated for up to 4 d aremore vigorous than the control seeds. Hence, such a presowingtreatment of seed could be used for seed invigoration. As theincubation proceeds, although a higher growth rate of seedlingsis obtained at optimal conditions, the tolerance to stress conditionsdeclines proportional to the duration of incubation. Results of chemical and biochemical examinations of the incubatedseeds are compared with those of seeds during normal imbibitionfor germination. The early stage of germination (up to 4 h)is accompanied by a decrease in reducing sugars and amino acids.At the later stage, an increase of these components and a decreasein the lipid fraction occur. During the first 4 h, an increaseand decrease of phosphoenolpyruvate carboxylase and of malicdehydrogenase occur. According to the chemical and biochemicalmarkers, it is evident that seed treatment at 20 °C and95% r.h. results in pregermination biochemical activities. Thefirst 4 d seem to be equivalent to the first 3 h of germinationunder normal conditons. At this period of time, degradationprocesses are taking place. If incubation is continued the resynthesisstage appears to be retarded by the low moisture available andtherefore degradation processes continue, resulting in lossof seed vigour. The resynthesis ability may therefore be a prerequisitefor the following steps in seed germination.     

人工老化处理对结球甘蓝种子生理生化特性的影响

以结球甘蓝品种‘冬升’种子为材料,研究高温(40℃)高湿(相对湿度100%)人工老化处理过程中种子的萌发特性、种子浸出液相对电导率和丙二醛、可溶性蛋白、可溶性糖含量以及抗氧化酶活性的变化,以揭示种子劣变的机理。结果表明:(1)人工老化处理甘蓝种子的含水量和不正常苗率均随着老化时间的延长逐渐增加,而种子发芽势、发芽率、发芽指数和活力指数的增加均逐渐降低。(2)随着处理天数的延长,老化处理甘蓝种子的浸出液电导率显著增大,浸出液可溶性糖含量逐渐升高,可溶性蛋白含量表现出显著下降趋势,而种子MDA含量呈先升高后逐渐下降的趋势。(3)在结球甘蓝种子老化进程中,其种子中SOD、POD、CAT活性变化的趋势相似,均随老化程度的加深而逐渐降低;而APX活性在老化处理的最初2d显著增加,第6天显著降低。研究发现,在结球甘蓝种子老化进程中,种子活力和萌发率显著降低,其种子浸出液电导率、可溶性蛋白含量、可溶性糖含量、保护酶活性变化与种子老化及劣变程度密切相关,膜脂过氧化作用可能是引起或加剧种子老化劣变的重要原因之一。     

Biochemical studies on biogenesis of mitochondria in wounded sweet potato root tissue I. Time course analysis of increase in mitochondrial enzymes

Cytochrome oxidase and succinate dehydrogenase activities increasedduring aging of sliced tissue for sweet potato root after respectivelag phases of about 8 and 10 hr. The increase in the formerwas stepwise. On the other hand, malate dehydrogenase activityincreased slowly without a lag phase. Spectrophotometric determinationof heme contents in mitochondria indicated that the hemes increasedafter a lag phase for at least 8 hr during aging Treatment of tissue slices with cycloheximide at a concentrationof 10^–6 M prior to aging resulted in an extension of thelag phase in the increase of cytochrome oxidaseactivity andin complete inhibition of the increase of malate dehydrogenaseactivity. The antibiotic, at a concentration of 10^–5 M,completely suppressed the increases. Chloramphenicol (6 ? 10^–3M) also blocked the increases, except for that in malate dehydrogenaseactivity at an early stage of aging (Received December 22, 1970; )     

防风种子发芽特性及促进发芽的试验研究

防风种子发芽率和发芽势均较低,其主要原因包括个体之间的差异及物种特性。种子发芽率较低首先表现在个体发芽率上的差异,试验所用15株防风发芽率从28.0%到92.0%,从整体 上表现发芽率较低。防风本身发芽率低,由于物种因素,种子刚刚采收后的休眠,个体之间解除休眠时间和进入衰老的时间不一致,致使所有的种子不能全部在同一时间进入发芽高峰,同时,防风发芽的启动日有所差异,15株防风启动日和发芽持续时间相差均为两周以上。采用5~50 mg·kg^-1 GA、1~10 mg·kg^-1 6-BA、1%KNO₃和3%H₂O₂可提高休眠防风种子的发芽率,GA、6-BA可除防风种子的休眠,而1% KNO₃和3% H₂O₂对解除休眠的种子无明显影响。采用多种微量元素,即10~100 mg·kg^-1 Mn²⁺、10 mg·kg^-1 Cu²⁺和1 mg·kg^-1 Mo对种子进行处理可显著提高防风种子的发芽率,提示在植株绿果期喷施该类元素也可提高防风种子的发芽率。采用GA、NAA处理幼果,也可以提高种子的发芽率。     

The influence of aerated hydration seed treatment on seed longevity as assessed by the viability equations

Aerated hydration (AH) treatments of cauliflower seeds for 12 h (12AH) and 28 h (28AH) at 20 degrees C resulted in improved or reduced storage potential of low or high vigour seeds, respectively. Seeds were stored at their initial seed moisture content (mean 5.5% mc) or at 12% mc at 10 degrees C for 12 months and at 20 degrees C for 4 months. The improved longevity of low vigour seeds was associated with increased K(i) (initial seed viability) and a reduced rate of deterioration (1/sigma) whereas the K(i) of high vigour seeds fell after 28AH and the rate of deterioration increased such that the time to lose one probit of viability decreased from 28.7 to 5.3 months at 10 degrees C and from 10.4 to 1.2 months at 20 degrees C. The improved K(i) of low vigour seeds could be explained by the reduction in the extent of deterioration after AH, as indicated by the increase in germination after cotrolled deterioration (CD), and the possible activation of metabolic repair during treatment. In contrast the reduced germination after CD of AH-treated high vigour seeds was indicative of deterioration as a result of treatment. Both high and low vigour seeds contained constitutive levels of ss-tubulin which increased during AH treatment, the increase being greater in high vigour seeds. High vigour seeds also showed an increase in the proportion of nuclear DNA present as 4C DNA, from 3% (untreated seeds) to 26% (28AH), indicative of germination advancement from the G(1) to G(2) phase of the cell cycle during treatment. This higher proportion of 4C DNA is correlated with the increased sensitivity of seeds to drying and/or storage after AH, leading to their reduced K(i) and storage potential. In contrast, there was little change in %4C in low vigour seeds. Priming in polyethylene glycol (PEG, -1.0 MPa) for 5 d or 13 d also improved the longevity of low vigour seeds stored at their initial and 12% mc at 10 degrees C for 8 months, as reflected in their laboratory and CD germination. In this case, however, the improved longevity of the low vigour seeds following 13 d priming was associated with an increase in 4C DNA from 4% (dry control) to 56% after treatment. The germination of both untreated and primed high vigour seeds remained high throughout the storage period. Increases in the rate of germination (decreased mean germination time) observed after all AH and PEG treatments were not consistently associated with an increase in the proportion of nuclei containing 4C DNA.     

The Role of Anaerobic Respiration in Germinating Muskmelon Seeds: II. EFFECT OF ANOXIA TREATMENT AND ALCOHOL DEHYDROGENASE ACTIVITY

Exposing muskmelon (Cucumis melo L.) cultivar seedlots to N₂atmosphere created totally anaerobic conditions which stimulatedethanol production and accumulation in both high and low vigourseeds. However, accumulation of ethanol was consistently higherin the low vigour seeds than in the high vigour ones. In addition,CO₂ production under N₂ and in air suggests the presence ofan apparent ‘Pasteur effect’ in the low vigour seedsbut not in the high vigour seeds. Acetaldehyde production underN₂ was very low and did not seem to be associated with seedvigour, probably because of its nature as an intermediate inethanol production. The fast shift toward ethanol may be dueto the fact that alcohol dehydrogenase, the enzyme which catalyzesthe conversion of acetaldehyde to ethanol, exists in sufficientamounts in the imbibing seeds so that it is not a limiting factorin the conversion to ethanol. Alcohol dehydrogenase activitydid not appear to be related to seed vigour. Key words: Cucumis melo L., Anaerobic respiration, Germination, Seeds.     

Photoperiodically Induced Changes in Seed Growth Rate of Soybean as Related to Endogenous Concentrations of ABA and Sucrose in Seed Tissues

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 seed^–1 d^–1 vs. 5·3 mgseed^–1 d^–1). On a tissue-water basis, the concentrationof ABA in SD seeds increased rapidly from 7.6 µmol l^–1at 11 DAA to 65·2 µmol l^–1 at 18 DAA, butthen declined to 6·6 µmol l^–1 by 39 DAA.In contrast, the concentration of ABA increased more slowlyin NI seeds, reaching only 47·4 µmol l^–1by 18 DAA, peaking at 57·0 µmol l^–1 on 25DAA, and declining to 10·2 µmol l^–1 by 39DAA. The concentration of sucrose in SD embryos peaked at 73·5mmol l^–1 on 25 DAA and remained relatively constant forthe remainder of the seed-filling period. In NI, the concentrationof sucrose reached only 38·3 mmol 1^–1 by 25 DAA,and peaked at 61·5 µmol l^–1 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     

Changes in oligosaccharide content and antioxidant enzyme activities in developing bean seeds as related to acquisition of drying tolerance and seed quality.

Seeds of bean (Phaseolus vulgaris cv. Vernel) were collected throughout their development on the plant and dried at 15 degrees C and 75% relative humidity to a final moisture content of about 16% (fresh weight basis) to determine whether the onset of tolerance to this drying condition was related to changes in soluble sugars or the activities of the main antioxidant enzymes, namely superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR). Measurements of soluble sugars and enzyme activities were made after drying the seeds, and drying tolerance was evaluated by the ability of dried seeds to germinate and to produce normal seedlings. Seeds became tolerant to drying at 45 d after anthesis, a time marking physiological maturity. At physiological maturity, the moisture content of seeds was about 50-55% (fresh weight basis) and seed dry matter reached about 190 mg per seed. Seed vigour, evaluated by controlled deterioration and conductivity measurements, continued to increase after seed mass maturity, but decreased when seeds remained thereafter for more than 7 d on the plant. Acquisition of drying tolerance was coincident with an accumulation of raffinose and stachyose. Dried-tolerant seeds were also characterized by a high amount of sucrose, the most abundant sugar, and by a low content of monosaccharides. The (raffinose+stachyose)/sucrose ratio increased during seed filling, reaching a value close to 1 when all the seeds became tolerant to drying, and maintaining this proportion during the final stages of maturation. Acquisition of drying tolerance was also related to a reorientation of the enzymatic antioxidant defence system. Drying-tolerant dried seeds displayed high CAT and GR activities and low SOD and APX activities, while the opposite condition was observed in immature dried seeds. The shift in antioxidant enzymes corresponded to the beginning of the maturation-drying phase. These results suggest that oligosaccharide metabolism and enzymatic antioxidant defences may be involved in acquisition of drying tolerance during bean seed development, but are not related to seed vigour.     

The Role of Anaerobic Respiration in Germinating Muskmelon Seeds: I. IN RELATION TO SEED LOT QUALITY

Five muskmelon (Cucumis melo L.) cultivar seedlots from a commercialsource and freshly produced seeds of two cultivars, when artificiallyaged, were found to differ in their viability and vigour asdetermined by germination tests. Furthermore, the various commercialseedlots without ageing also exhibit a range of deteriorationlevels. Low vigour seeds had higher respiratory quotient valuesthan the high vigour seeds as a result of a higher level ofCO₂ production. This high level of CO₂ evolution in low vigourseeds may have been due to anaerobic respiration. Levels of acetaldehyde and ethanol produced by imbibing seedswere negatively associated with seed viability and vigour. After6 h of imbibition low vigour seeds produced significantly moreethanol and acetaldehyde than high vigour seeds. After 24 hof imbibition, ethanol continued to accumulate in the commercialseedlots up to 10-fold the amount produced after 6 h of imbibition,whereas, acetaldehyde levels increased less. However, in thefreshly produced, artificially aged seeds (except the most extremeageing), ethanol levels were reduced and no acetaldehyde productioncould be detected, indicating re-utilization of ethanol. It is suggested that ethanol production in the first hours ofimbibition can be used as a reliable index to predict germinationin muskmelon seedlots. Key words: Germination, Cucumis melo L., Seeds, Anaerobic respiration     

Seed Selection for Potential Viability

A simple method is presented for selecting individual seedsfor growth and vigour prior to germination. The selection isbased on the measurement of an electric current originatingduring the initial stage of seed imbibition. After selecting,seeds may be returned to the quiescent state without affectingviability. Results of both laboratory germination and fieldexperiments demonstrate that high germination rates, more extensivegrowth, higher yields, and fewer defective plants are associatedwith small currents. Seeds of low viability and high currentsmay be removed to upgrade the germination and vigour. Resultsare presented from several varieties of Phaseolus vulgaris andfrom three other plant species. Experiments are discussed whichindicate that seeds graded by current levels possess markedlydifferent respiration rates.     

Winterfat (Eurotia lanata(Pursh) Moq.) Seedbed Ecology: Low Temperature Exotherms and Cold Hardiness in Hydrated Seeds as Influenced by Imbibition Temperature

Thermal analyses of freezing events in hydrated lettuce (LactucasativaL.) seeds show a correlation between low temperature exotherms(LTEs) (evidence of ice crystal formation) and seed death. Yet,weather patterns common to the Northern Great Plains of NorthAmerica regularly create conditions where non-dormant seedsof native plants hydrate with snow melt and are subsequentlyexposed to -30 °C or colder conditions. To determine ifsuch weather patterns decimate dispersed seeds, we measuredthe effects of freezing on fully hydrated winterfat (Eurotialanata(Pursh) Moq.) seeds harvested from the Northern Plainsat two USA and one Canadian location. Survival of hydrated seedsto -30 °C at a cooling rate of 2.5 °C h^-1was similarto that of seeds not subjected to cooling, even though botha high temperature exotherm (HTE) and an LTE were observed.Although the LTE was not related to winterfat seed survival,freeze-stressed seeds had reduced germination rates and reducedseedling vigour, particularly for the collection with the lightestseeds. The temperature of LTEs was similar among seed collectionswith a mean of -17.6 °C, but was warmer when the seeds wereimbibed at 0 °C compared to 5, 10 or 20 °C. We founda significant correlation between the HTE and LTE temperatures.The difference and the correlation may be due to the highermoisture content of seeds imbibed at 0 °C. After pericarpremoval, only one exotherm in the range of the LTE was observed.This was also true for the naked embryo. We conclude that anLTE indicates ice formation in the embryo, but that it doesnot signal the death of a winterfat seed.Copyright 1998 Annalsof Botany Company Eurotia lanata(Pursh) Moq.,Krascheninnikovia, Ceratoides,winterfat, exotherm, freezing tolerance, freezing avoidance, seedbed ecology, germination, D50, seedling vigour, seed collection     

Carbon and Nitrogen Transfer from Vegetative Organs to Ripening Seeds of Field Pea (Pisum arvense L.)

The fate of the carbon from photosynthetically assimilated ¹⁴CO₂and the nitrogen of rootapplied ¹⁵NO₃ was studied by harvestingplants at intervals after a week's feeding period, either early(34–41 d after sowing) during vegetative growth, or late(112–19 d) as plants were fruiting. Only 23 per cent of the early fed ¹⁴C but more than 90 per centof the early-fed ¹⁵N survived in plants until maturity (155d). Efficiency of transfer of early-fed ¹⁴C to seeds was 2 percent, that for early-fed ¹⁵N, 51 per cent. Assimilatory activitybefore flowering had little direct relevance to the carbon nutritionof seeds but provided approximately one-fifth of the seeds'requirement for nitrogen. Early or late-fed ¹⁵N was mobilized slowly for reproductivedevelopment, seeds at all 15 reproductive nodes deriving benefit,late-forming ones more so than those developing earlier. Vegetative organs on a young shoot lost previously acquired¹⁵N at rates within the range 0.5–2.4 per cent per day.The released nitrogen was first taken up by the root and youngerparts of the shoot, but much was later traced to the seeds. Late feeding of ¹⁴C or ¹⁵N resulted in a high (74–6 percent) efficiency of transfer to seeds, most of this appearingto be donated by, or cycled through, vegetative parts of thereproductive zone of the shoot. The significance of past and current assimilation in fruit nutritionis discussed.     

Kinetics of Phenylalanine Ammonia-Lyase and the Effect of L-{alpha}-aminooxy-{beta}-phenylpropionic Acid on Enzyme Activity and Radicle Growth in Germinating Lettuce Seeds

The effects of different concentrations of L--aminooxy-ß-phenyIpropionicacid (AOPP), an analog of L-phenylalanine, on the activity ofphenylalanine ammonia-lyase (PAL, EC 4.3.1.5 [EC] ) and the growthof radicles in 24 h old germinating lettuce (Lactuca salivaL.) seeds were investigated. AOPP causes a significant inhibitionof PAL activity in the seeds (85% inhibition at 10⁴ M). It alsocauses a stimulation of radicle growth at that concentration.The results show that the inhibition of PAL by AOPP may be dueto an irreversible binding of the inhibitor to the enzyme leadingto its inactivation. AOPP also inhibits ethylene biosynthesisin germinating lettuce seeds which could probably explain thestimulation of radicle growth in these seeds. The enzyme shows typical Michaelis-Menten kinetics. The K_m forL-phenylalanine is 4.2 x 10⁵ M. The enzyme does not show anytyrosine ammonia-lyase activity. Various substrate analogs suchas D-phenylalanine, p-fluorophenylalanine, ß-phenyllacticacid, tryptophan and the product of the enzyme reaction, trans-cinnamicacid, inhibit the enzyme competitively. A number of intermediatesand endproducts of the phenylpropanpid pathway, except chlorogenicacid, do not show any inhibition. ¹Scientific contribution number 1423 from the New HampshireAgricultural Experiment Station. (Received May 9, 1986; Accepted September 8, 1986)     

不同活力玉米种子胚萌发过程中蛋白质的变化

从不同人工老化处理中筛选出３组分别代表不同活力的玉米种子。萌发期间,中、低活力种子胚蛋白的降解比高活力对照种子慢,萌发前期胚蛋白合成能力也较低。吸胀２４ｈ,不同活力胚的蛋白合成能力差异显著,可以作为衡量种子活力的指标。     

Ageing of Cucumber and Onion Seeds: Phospholipase D, Lipoxygenase Activity and Changes in Phospholipid Content

Cucumber (Cucumis sativus L. cv. Mesa) and onion (Allium cepaL. cv. Rijnsburger Heldis) seeds were rapidly aged at 40 °Cand 74% relative humidity. Onion seeds were also slowly agedat 40 °C with 15% relative humidity for 11 months and onemore month at 28% relative humidity. Significant loss of totaland individual phospholipids was an early event during bothstorage treatments. With slow ageing of onion, loss of phosphatidylcholineoccurred several months before loss of viability and vigourwas detected. Phosphatidic acid, the lipid product of phospholipaseD action, increased during rapid ageing of both cucumber andonion. Phosphatidic acid was present in onion seeds before theageing treatments and its content remained unchanged in theslowly aged seeds. There was 1600 (cucumber) and 2000 (onion)times more phospholipase D activity (6 x 10⁵ and 2·9x 10⁵ nmol g^–1 d^–1 in cucumber and onion, respectively)in crude extracts from non-aged seeds than was required to accountfor the fastest fall in phospholipids (72, 372 and 144 nmolg^–1 d^–1 for cotyledons and radicles of cucumberand onion, respectively, over the first 9 d [cucumber] or 1d [onion] of ageing) and fastest increase in phosphatidic acid(7, 162 and 37 nmol g^–1 d^–1). How accurate a guidethe in vitro activity of phospholipase D was to the in vivoactivity was unclear. However, the considerable excess activityseen with the formation of phosphatidic acid supports the proposalthat hydrolysis of phospholipids by phospholipase D is a firststep in deterioration during ageing. Substantial lipoxygenaseactivity was also detected (58 x 10³ and 54 x 10³ nmol g^–1d^–1 respectively, for non-aged cucumber and onion seeds).However, the increase in conjugated dienes (an early productof peroxidation) in ageing cucumber seeds was comparativelysmall (90 nmol g^–1 d^–1 over 21 d ageing), and increasein malondialdehyde could not be detected, indicating that peroxidationmay not have been a major factor in cucumber. The increase inconjugated dienes during rapid ageing of onion seeds was larger(1·5 x 10³ nmol g^–1 d^–1 over days 0–2of rapid ageing), much greater than the decrease in phospholipidacyl groups (260 nmol g^–1 d^–1 over days 0–2of rapid ageing) indicating the occurrence of peroxidation offatty acids released from reserve as well as from membrane lipids.This higher level of conjugated dienes during onion ageing wasthe main difference between cucumber and onion, indicating thatthe level of peroxidation could be an important difference betweenfast and slow ageing seeds. However, peroxidation is not theonly possible deleterious process since hydrolysis of the normalmembrane phospholipids to phosphatidic acid increased the contentof non-bilayer-forming lipids and this too could be a directmembrane-destabilizing consequence of phospholipase D actionduring ageing. Key words: Cucumis sativus L. (cucumber), Allium cepa L. (onion), seed ageing, phospholipase D, lipoxygenase, phospholipids     

Priming and accelerated ageing affect L-isoaspartyl methyltransferase activity in tomato (Lycopersicon esculentum Mill.) seed

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 1–4 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     

The mitochondrial energy transduction system and the aging process

Aged mammalian tissues show a decreased capacity to produce ATP by oxidative phosphorylation due to dysfunctional mitochondria. The mitochondrial content of rat brain and liver is not reduced in aging and the impairment of mitochondrial function is due to decreased rates of electron transfer by the selectively diminished activities of complexes I and IV. Inner membrane H⁺ impermeability and F₁-ATP synthase activity are only slightly affected by aging. Dysfunctional mitochondria in aged rodents are characterized, besides decreased electron transfer and O₂ uptake, by an increased content of oxidation products of phospholipids, proteins and DNA, a decreased membrane potential, and increased size and fragility. Free radical-mediated oxidations are determining factors of mitochondrial dysfunction and turnover, cell apoptosis, tissue function, and lifespan. Inner membrane enzyme activities, such as those of complexes I and IV and mitochondrial nitric oxide synthase, decrease upon aging and afford aging markers. The activities of these three enzymes in mice brain are linearly correlated with neurological performance, as determined by the tightrope and the T-maze tests. The same enzymatic activities correlated positively with mice survival and negatively with the mitochondrial content of lipid and protein oxidation products. Conditions that increase survival, as vitamin E dietary supplementation, caloric restriction, high spontaneous neurological activity, and moderate physical exercise, ameliorate mitochondrial dysfunction in aged brain and liver. The pleiotropic signaling of mitochondrial H₂O₂ and nitric oxide diffusion to the cytosol seems modified in aged animals and to contribute to the decreased mitochondrial biogenesis in old animals. oxidative damage; survival; complexes I and IV; nitric oxide synthase     

高温加速老化过程中甜菜种子线粒体小分

甜菜(BetavulgarisLcv.Loke)种子的人工老化(30℃,100％RH)导致种子的干重、生活力和活力逐渐丧失,线粒体的呼吸速率、细胞色素c氧化酶和苹果酸脱氢酶的活性下降。线粒体蛋白质随着种子老化而显著变化,小分子量热休克蛋白(LMWHSP)22从老化的0d到30d增加,然后从30d到90d下降。可以认为甜菜种子人工老化过程中线粒体活性和LMWHSP22的含量变化与种子活力密切相关。