Wheat Viability at High Moisture Content under Hermetic and Aerobic Storage Conditions

Wheat seeds (Triticum durum) were stored under both hermeticand aerobic conditions at 25 °C with moisture contents from15 to 33 per cent. Under hermetic storage, seeds lost viabilitymore rapidly the higher the moisture content, whereas in aerobicstorage, seed longevity was enhanced as the moisture contentwas increased from 24 to 31 per cent, and over this range ofmoisture content the seeds survived longer under aerobic thanhermetic storage. On the contrary, an apparent reversal of thistrend occurred when moisture content was increased above 31per cent. The possibility that the changes in longevity occurring at highermoisture contents might be due to the activation of seed metabolismwas supported by the enhanced incorporation of [³H]leucine intoTCA insoluble material (indicating increased protein synthesis)and the reduced leakage of glucose (indicating increased membranerestitution) when seeds were allowed to achieve higher moisturecontents during the prehydration period. The highest level ofseed activation was found in seeds preconditioned to about 31per cent moisture content. Moreover, these seeds, when subsequentlystored under aerobic conditions, maintained a higher rate ofprotein synthesis and lower membrane permeability during thestorage period than seeds at lower water contents. It is suggested that seeds stored at a sufficient hydrationlevel in the presence of oxygen can sustain an effective metabolismduring extended storage, thus permitting the repair of cellulardamage. However, it might be possible that at about 33 per centmoisture content seed could suffer from an excessive advancementof metabolism. Triticum durum, seed storage, effects of high moisture content and oxygen     

Studies on the Structure,Afterripening and Cytochemistry of Seeds in Eleutherococcus brachypus Harms

Seeds of Eleutherococcus brachypus Harms were flat-kidney-shaped and their seed coats were only composed of one layer of cells. Embryos with abundant protein in their cells were just at the heart-shaped stage and were capped by sacs formed from degenerating endosperm cells when seeds shed from their maternal plants. A large amount of stored protein grains and lipids existed in endosperm cells but no polysaccharide grains were present either in endosperm cells or in embryo cells. Viable seeds were only 9.27% of the total. The plump seeds germinated in the cultivated field after 18～19 months and their germinating rate was 1.67%. Besides, the content of protein decreased gradually and a few polysaccharide grains were stored in embryo cells during the process. The afterripening process of seeds stratified at different temperatures ended after 6 months and the cytochemistry features of the seeds were that the content of protein decreased gradually and numerous polysaccharide grains had been stored in embryo cells at the late heart-shaped embryo stage and retained till the mature embryo stage. The structure, afterripening and cytochemistry of seeds were compared between Eleutherococcus brachypus and Eleutherococcus senticosus. The poor quality of the seeds, longer time of afterripening in a natural state and much lower germination rate of E. brachypus are considered to be important reasons for the endangerment of this species. Somemeasures are suggested for its conservation based on the above facts.     

The storage of green coffee (Coffea arabica): decrease of viability and changes of potential aroma precursors

BACKGROUND AND AIMS: When green coffee is stored for a prolonged time the coffee quality decreases distinctively. Apart from well-known 'off-notes' that arise from undesired oxidations of lipids, a typical 'flattening' of the cup quality is detectable. In order to elucidate the biological causes for this phenomenon, differentially processed coffees (wet, dry, semi-dry processing), were stored under standard conditions for 2 years and analysed comprehensively. METHODS: Wet-processed coffee was stored either as parchment coffee, where the endocarp remained around the beans or as hulled beans. Viability of coffee seeds was estimated using the tetrazolium-test of seed viability. Changes in concentration of free amino acids and soluble carbohydrates were analysed by HPLC. KEY RESULTS: Whereas all other coffees lost viability within the first 6 months of storage, coffee beans stored within the parchment remained viable for >1 year. Glucose and fructose decreased slightly in the course of storage and glutamine content declined significantly. However, the changes observed in sugar and amino acid content were not correlated with the viability of the coffee beans. Consequently, neither typical metabolic reactions occurring within living cells nor characteristic post-mortem reactions could be responsible for the observed changes. As a result of post-mortem reactions in re-imbibed seeds, a characteristic bluish-green colour developed, putatively due to the oxidation of chlorogenic acids and subsequent reactions with primary amino compounds. This coloration might be an appropriate marker to substantiate if coffee seeds had been stored for an expanded time and putative quality losses were not relevant so far. CONCLUSIONS: It is suggested that loss of viability is relevant for the aroma flattening. As neither metabolic nor post-mortem reactions were responsible for the observed changes, it is concluded that Maillard reactions that occur during storage might be the cause of the decrease in potential aroma precursors.     

Do Conditions During Dormancy Influence Germination of Suaeda maritima?

Background and Aims

Seeds of annual halophytes such as Suaeda maritima experience fluctuating salinity, hydration, hypoxia and temperature during dormancy. Germination then occurs in one flush of 2–3 weeks after about 5 months of winter dormancy during which time the seeds can remain in saline, often waterlogged soil. The aim of this study was to investigate the effect of simulated natural conditions during dormancy on germination and to compare this with germination following the usual conditions of storing seeds dry. The effects of hydration, salinity, hypoxia and temperature regimes imposed during dormancy on germination were investigated. Also looked at were the effects of seed size on germination and the interaction between salinity during dormancy and salinity at the time of germination.

Methods

Various pre-treatments were imposed on samples of seeds that had been stored dry or wet for different periods of time during the 5 months of natural dormancy. Subsequent germination tests were carried out in conditions that simulated those found in the spring when germination occurs naturally. Various salinities were imposed at germination for a test of interaction between storage salinity and salinity at germination.

Key Results

A temperature of about 15 °C was needed for germination and large seeds germinated earlier and better than small seeds. Cold seawater pre-treatment was necessary for good germination; the longer the saline pre-treatment during the natural dormancy period the better the germination. There appeared to be no effect of any specific ion of the seawater pre-treatment on germination and severe hypoxia did not prevent good germination. A short period of freezing stimulated early germination in dry-stored seed. Storage in cold saline or equivalent osmotic medium appeared to inhibit germination during the natural dormancy period and predispose the seed to germinate when the temperature rose and the salinity fell. Seeds that were stored in cold wet conditions germinated better in saline conditions than those stored dry.

Conclusions

The conditions under which seeds of S. maritima are stored affect their subsequent germination. Under natural conditions seeds remain dormant in highly saline, anoxic mud and then germinate when the temperature rises above about 15 °C and the salinity is reduced.Key words: Suaeda maritima, germination, pre-treatment, salinity, temperature     

RNases and nucleases in embryos and endosperms from naturally aged wheat seeds stored in different conditions

Temperature and moisture content are particularly important factors influencing the longevity of seeds, and therefore the ageing of seeds is closely tied to storage conditions. The ageing process is characterised by many physiological and biochemical changes: membranes tend to leak, enzymes lose catalytic activity, and chromosomes accumulate mutations. Since viability loss is also associated with the breakdown of nucleic acids, the aim of the study was to determine whether the damage induced by ageing could be associated with changes in the activity of RNases and nucleases in embryos and endosperms of differently stored wheat seeds. In order to better characterise seed conditions, the damage to membranes during seed ageing was evaluated by measuring the conductivity of the soaking solution during imbibition, and by using the Evans Blue colorant; lipid peroxidation was also recorded. RNases and nucleases were studied by SDS-PAGE and activity staining. Ageing of seeds stored in a dry state involved a progressive loss of membrane integrity, which increased with the degree of ageing, while lipid peroxidation remained unchanged. Changes in nucleolytic enzyme activity were recorded in embryos: a decrease in RNases and an increase in nucleases. In the endosperm compartment there were no significant differences in ribonuclease and nuclease patterns during seed ageing. Moreover, neutral RNases were absent in endosperms of dry seeds and were activated following imbibition. Present studies reveal that embryos and endosperms have different enzymatic patterns, thus highlighting that the two seed compartments age independently. A different nucleolytic pattern was present in seeds of comparable viability and membrane damage, which were stored differently, and nuclease metabolism was subject to regulation according to both ageing and the length of the storage period.     

Possible involvement of volatile compounds in the after-ripening of cocklebur seeds

The mechanism of emergence from primary dormancy, the process of after-ripening, in cocklebur (Xanthium pennsylvanicum) seeds was examined in relation to the involvement of volatile compounds and to the relative humidity (RH) in which the seeds were stored. The after-ripening of these seeds proceeds only at water contents between 7 and 14% which are conditioned under RHs of 33% to 53% and are identified with water-binding region II. After-ripening of cocklebur seeds occurred even in water-binding region I. imposed by 12% RH. when exposed to HCN gas during the storage period. Exposure of dormant seeds to acetaldehyde (ethanal) retarded after-ripening. even in water-binding region II. thus decreasing germinability. This decrease of germinability by ethanal was found also in the after-ripened seeds, suggesting that ethanal accelerates seed deterioration rather than retarding the after-ripening. The contents of ethanal. ethanal and HCN were high only in the dormant seeds held at 12% RH. Regardless of RH. a possible conversion of ethanal to ethanol. perhaps via alcohol dehydrogenase. was far larger in dormant than in non-dormant seeds. In contrast, the reverse conversion of ethanol to ethanal was more profound in non-dormant seeds. Pre-exposure of both types of seeds to HCN reduced the contents of both ethanal and ethanol at 12% RH. The contents of various adenylales including ATP in seed tissues were higher in dormant seeds stored at 12% RH than in non-dormant seeds after-ripened at 44% RH. It is suggested that emergence of cocklebur seeds from primary dormancy by HCN treatment at 12% RH may result from the reduction in the contents of ethanal via an unknown mechanism incurring the consumption of ATP. This implies involvement of volatile compound metabolism at the water-binding region II in the after-ripening process of cocklebur seeds.     

Reducing storage requirements for biological sequence comparison

MOTIVATION: Comparison of nucleic acid and protein sequences is a fundamental tool of modern bioinformatics. A dominant method of such string matching is the 'seed-and-extend' approach, in which occurrences of short subsequences called 'seeds' are used to search for potentially longer matches in a large database of sequences. Each such potential match is then checked to see if it extends beyond the seed. To be effective, the seed-and-extend approach needs to catalogue seeds from virtually every substring in the database of search strings. Projects such as mammalian genome assemblies and large-scale protein matching, however, have such large sequence databases that the resulting list of seeds cannot be stored in RAM on a single computer. This significantly slows the matching process. RESULTS: We present a simple and elegant method in which only a small fraction of seeds, called 'minimizers', needs to be stored. Using minimizers can speed up string-matching computations by a large factor while missing only a small fraction of the matches found using all seeds.     

Cyclic dormancy,temperature and water availability control germination of Carrichtera annua,an invasive species in chenopod shrublands

Abstract We studied the germination of seeds of Carrichtera annua L. from a single cohort, stored in the field for up to 18 months, when retrieved at different times and subject to different combinations of temperature and water availability. Germination was affected by season of retrieval, and temperature and water availability in a complex interactive way. Germination rates were lowest when seeds were retrieved during summer or spring, but seeds germinated readily when retrieved during autumn and winter, if exposed to temperatures simulating autumn or winter conditions, and provided water equivalent to at least 50% field capacity. High temperatures and low water availability reduced germination substantially. The results indicate that this species has a combination of cyclic dormancy and germination requirements that minimizes the risk of germination during periods when the risk of prereproductive mortality is high. Given the short life of the seeds of this species, these mechanisms may be essential for the persistence of the species in the highly unpredictable arid lands of southern Australia.     

Changes in late embryogenesis abundant proteins and a small heat shock protein during storage of beech (Fagus sylvatica L.) seeds

Beech seed physiology, including the effect of stress proteins like late embryogenesis abundant (LEA) and small heat shock proteins (sHSP) on viability during storage, is not fully understood. Four lots of beech (Fagus sylvatica L.) seeds have been stored for 1, 4, 6 and 8 years at −10 °C and 8–9% moisture content (MC). Under these conditions, the germination capacity ranges from 81.5% to 100% in the youngest seeds. However, the seeds decrease in vigour with prolonged time of storage. Dehydrins and dehydrin-like proteins were identified both in cotyledons and embryonic axes of the dry stored seeds. In general, decreased contents of LEA proteins as well as reduced content of total soluble protein were detected during prolonged storage. The contents of soluble proteins in embryonic axes and nearly all detected dehydrins and dehydrin-like proteins were correlated with germination capacity. Moreover a sHSP with molecular mass of approximately 22 kDa was identified. The largest content of this protein was observed in the oldest seeds, especially in embryonic axes. The proteins identified may play a protective role during water deficit and storage.     

Influence of Storage Period and Temperature on Viability and Chemical Composition of Cotton Seeds

The investigation reported here includes measurements of germinationpercentage, contents of oilstarch, protein, moisture, and temperatureof cotton seeds during storage from the two varieties underproduction in the Gezira Scheme. The germination percentageof the seeds decreased during 16 months of storage and resultsindicated that the deterioration in the viability of the seedswas associated with a decline in oil content. During a shorterperiod of 9 months, a drop in germination percentage was onlyfound in seeds stored in positions characterized by high temperatureswhich fluctuated widely. Germination percentage and proteincontent decreased linearly with an increase in temperature;and germination percentage was correlated with protein content,suggesting that the decline in germination percentage mighthave been partly brought about by the decrease in protein content.     

东北刺人参种子萌发影响因子的研究

东北刺人参(Oplopanax elatus Nakai)种子透水性良好,休眠后萌发不受其影响.种皮和胚乳的水提取物中存在萌发抑制物质,胚乳中提取物对白菜种子萌发的抑制效果比种皮更明显.种子自然脱落时胚尚未分化完全,处于心形胚阶段.种子需要先温暖层积以完成胚的分化与生长,然后转入低温层积完成生理后熟.同批种子胚的发育不完全同步,变温层积处理7个月有极少数种子萌发,连续变温层积处理17个月大部分种子萌发.不同年份受气候条件影响,种子产量和发芽率差异较大.种子耐贮性较强,贮藏2年的种子生活力变化不大,仍具有较高的萌发潜力.     

东北刺人参种子萌发影响因子的研究

东北刺人参(Oplopanax elatus Nakai)种子透水性良好,休眠后萌发不受其影响。种皮和胚乳的水提取物中存在萌发抑制物质,胚乳中提取物对白菜种子萌发的抑制效果比种皮更明显。种子自然脱落时胚尚未分化完全,处于心形胚阶段。种子需要先温暖层积以完成胚的分化与生长,然后转入低温层积完成生理后熟。同批种子胚的发育不完全同步,变温层积处理7个月有极少数种子萌发,连续变温层积处理17个月大部分种子萌发。不同年份受气候条件影响,种子产量和发芽率差异较大。种子耐贮性较强,贮藏2年的种子生活力变化不大,仍具有较高的萌发潜力。     

Auxins, Inhibitors and Phenolics in Bambarranut Seeds (Voandzeia subterranea Thouars) in Relation to Loss of Viability During Storage

Studies were made on seeds of bambarra groundnut (Voandzeiasubterranea Thouars) after 0, 6, 12, 18 and 24 months of storage. Germinability of the seeds was not adversely affected up to12 months of storage but it rapidly declined and after 24 monthsstorage no germination occurred. Growth of seedlings starteddecreasing in seeds stored for 12 months or more. Closely coincidingwith this, there was an increase in the contents of total phenoland inhibitory phenolic acids (p-hydroxybenzoic, p-coumaric,feruhc and vanillic acids) and a decrease in synergistic phenolicacids (chlorogenic, sinapic and protocatechuic acids). Auxincontent decreased in seeds stored for 18 months or more whilegrowth inhibitors appeared after 12 months of storage and increasedthereafter. Non-viable bambarranut seeds contained larger amounts of totalphenol, inhibitory phenolic acids and other growth inhibitorsand lower amounts of auxin and synergistic phenolic acids comparedwith the viable ones. Voandzeia subterranea Thouars, bambarranut, seed storage, germination, viability, auxins, inhibitors, phenol, phenolic acids     

顽拗性竹柏种子的贮藏特性

文章对竹柏(Podocarpus nagi)种子的脱水耐性和贮藏特性进行了研究,结果表明:竹柏种子成熟时初始含水量约为(35±0.7)%,种子对脱水敏感,其最低安全含水量约为(16.86±0.73)%,具有顽拗性种子的典型特征;湿藏和半干藏都可以作为短期保存竹柏种子的方法,且以4℃保存优于15℃保存,但不管种子含水量如何,零下低温保存对竹柏种子都是致命的;半干藏法保存实验中,未进行脱水处理的种子(对照)在4℃贮藏6个月,种子萌发率没有发生明显下降,但贮藏期延长到9个月时,临界含水量的种子萌发力保存最高;不管贮藏介质的含水量高低,也无论贮藏在4℃还是15℃,湿藏种子在9个月的贮藏期内萌发率均没有明显的降低,但当贮藏到12个月时,15℃湿藏种子的萌发率显著高于4℃贮藏的种子,但15℃湿藏的种子在贮藏到3个月时即发现种子在贮藏期间萌发,且随着贮藏介质含水量的升高和贮藏期的延长,萌发的种子增多;竹柏的离体胚经过2 h硅胶快速脱水至含水量7%后再冷冻即可获得90%以上的融后存活率,且超低温保存1年的离体胚解冻后,与只保存1周的存活率没有明显差异,表明超低温长期保存竹柏种子是可行的。本研究可以为进一步探究顽拗性种子的短期贮藏和长期保存提供理论基础和基础资料。     

Phosphorus metabolism during ripening ofGlycine max. (L.)Merril

The seeds, seed covers and leaves, taken after 17, 27, 37, and 47 days after tagging of flowers of soybean, were analysed quantitatively for their contents of different phosphorus fractions. Total phosphorus content increased in seed cover and leaves, there was a gradual decrease during ripening. All the phosphorus fractions i.e. acid soluble—P, lipid—P, nucleic acid—P, and protein—P were found to increase with maturity in seeds whereas in case of seed covers the content of acid soluble—P, nucleic acid—P and protein—P decreased but a marked increase was observed in lipid—P. In leaves during ripening, all the phosphorus fractions decreased except protein—P which was found to be almost constant. In lipid—P an increase was observed during later stages of maturity.     

中国特有植物凹叶木兰种子的休眠与贮藏行为

凹叶木（Magnoliasargentiana）是中国特有的观赏树木,种群的自然更新很差,须阐明其原因。研究发现,凹叶木兰种子的胚很小,无论是否被植物生长调节剂预处理,在冷层积（4℃）和暖层积（15℃）过程中,胚在种子内逐渐生长发育成熟,并能在多个温度下萌发,以变温30℃／20℃为最适宜。由此可见,凹叶木兰种子不能萌发的直接原因是形态休眠。此外,凹叶木兰种子较耐脱水,但干燥脱水至含水量为7．1％和5．3％时,种子的存活率分别是78．3％和40％。保存6个月后,含水量为9．4％或7．1％的种子在-20℃下全部失活,而在0和4℃下的种子,存活率无显著变化,充分证实凹叶木兰种子是中间性的。     

模拟四季温度层积对南方红豆杉种子生理性状的影响

为了解濒危物种南方红豆杉(Taxus chinensis var. mairei)种子内含物含量受温度和湿度层积的影响,设置4个季节、2种湿度(16%和24%)基质层积处理,对种子的可溶性糖、淀粉、可溶性蛋白和脂肪等内含物质的变化进行研究。结果表明,不同层积处理下种子贮藏物质的含量有显著变化,春季层积9个月后,可溶性蛋白含量达到最高值;可溶性糖含量呈现降低-升高-降低的变化趋势;淀粉和脂肪含量均随层积逐渐减少。秋季层积9个月后,淀粉含量降至最低。相比于24%湿度,16%湿度的春季、秋季、冬季层积9个月后,脂肪含量均减少较多,说明16%湿度下种子代谢活动更强。春季和秋季的暖温更能促进种子代谢,促进种子形态后熟。夏季温度过高,导致种子生活力下降,夏季层积处理3个月后,种子已经发霉和腐烂。层积过程中,种子内含物在相关酶的作用下,降解为可溶性蛋白、可溶性糖等,为种子萌发提供物质与能量。种子层积时间、温度和湿度及交互作用可作为种子内含物的调控因子。     

The increasing desiccation sensitivity of recalcitrant Avicennia marina seeds with storage time

To test the hypothesis that desiccation sensitivity increases with storage time, recalcitrant seeds of Avicennia marina (Forssk.) Vierh. were dehydrated by soaking in polyethylene glycol solutions after inreasing periods of storage. Germination characteristics and the ultrastructure of root primorida were assessed before and after dehydration. Short-term storage enhanced the apparent rate of germination, consistent with the hypothesis that these seeds commence germination in storage. Root primordia of stored seeds initially showed enhanced subcellular activity, including cell division and vacuolation. Increased storage time resulted in the onset and progression of deleterious changes.
Newly shed seeds and seeds stored up to the stage of cell division were comparatively resistant to desiccation. As storage time increased, subsequent dehydration caused increasing subcellular damange and consequent reduction in the rates of germination relative to non-dehydrated controls. Ultrastructural results suggest that after the initiation of cell division of seeds in storage, there is a requirement for additional water for the germination process to continue. A model for the behaviour of recalcitrant seeds is proposed.     

Mycoflora and aflatoxin production in pigeon pea stored in jute sacks and iron bins

The mycoflora, moisture content and aflatoxin contamination of pigeon pea (Cajanus cajan (L.) Millisp) stored in jute sacks and iron bins were determined at monthly intervals for a year. The predominant fungi on freshly harvested seeds wereAlternaria spp.,Botryodiplodia theobromae, Fusarium spp. andPhoma spp. These fungi gradually disappeared from stored seeds with time and by 5–6 months, most were not isolated. The fungi that succeeded the initially dominant ones were mainly members of the generaAspergillus, Penicillium andRhizopus. Population of these fungi increased up to the end of one year storage. Higher incidence of mycoflora andAspergillus flavus were recorded in jute-sack samples throughout the storage period. The moisture content of stored seeds was found to fluctuate with the prevailing weather condition, being low during the dry season and slightly high during the wet season. The stored seeds were free of aflatoxins for 3 and 5 months in jute sacks and iron bins respectively. The level of aflatoxins detected in jute-sack storage system was considerably higher than that occurring in the iron bin system. Of 196 isolates ofA. flavus screened, 48% were toxigenic in liquid culture (54% from jute sacks and 41% from iron bins).     

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.