植物种子寿命的生理及分子机制研究进展

种子寿命是衡量种子质量高低的关键指标之一,直接关系到种子萌发、萌发后幼苗的生长发育以及作物产量高低。种子寿命的调控是一个复杂的生物学过程,影响种子寿命的因素包括环境因素、种子自身的结构、营养成分组成及含量以及调控种子寿命相关的关键基因。研究储藏过程中种子生理生化指标的变化,以及相应关键基因的生物学功能,掌握调控种子寿命的生理及分子机制,对于减少种子内部能量消耗,进一步延长种子寿命具有重要意义。该文综述了近年来国内外有关调控种子寿命的生理及分子机制,重点阐述了调控种子寿命的相关关键基因的研究进展,并讨论了各种外部因素对种子寿命的调控机理。     

第四届国际种子生态学大会综述

第四届国际种子生态学大会于2013年6月22—26日在中国沈阳举行,共收到136份摘要,从进化种子生态学、种子传播、种子库、种子萌发与休眠、种子寿命和储藏、种子生态与植物多样性保护及植被恢复的关系等6个方面展示了种子生态学研究的进展。本文对这些研究进行了梳理,旨在为从事种子生态学研究的学者提供信息和指导。     

种子超干保存新技术

种子含水量和贮藏温度是影响种子贮存寿命的两个最重要因子,适当降低种子含水量和贮藏温度均可有效延长种子寿命。但长期以来受干燥技术上的限制和脱水方法不当,很难将种子含水量降至５％以下,加上忽略种子萌发前“再水合”过程中吸胀损伤的预防和渗控,致使普遍认为种...     

一个预测贮藏在低温种质库的小麦种子寿命的方程

为探讨将种子发芽率转化为存活比,促使种子存活曲线转变成直线,并用于预测种子寿命的可行性,3个含水量水平的3种8个种子批的小麦种子被贮藏在20℃、30℃和40℃的温度下长达810d,以获取发芽率数据。比较和分析了概率、存活比与贮藏时间绘制的种子存活曲线、构建的概率回归和存活比线性回归方程的拟合性比,以及贮藏温度和种子含水量对种子死亡时间分布标准差的影响。结果表明,和概率值相比,存活比更容易使种子存活曲线直线化,和贮藏时间的线性回归方程的拟合性也更优于概率回归方程;贮藏温度和种子含水量的交互作用对种子寿命的影响是真实的,其作用也大于单独的温度、水分或水分的对数;只包含贮藏温度和种子含水量交互作用的预测种子寿命的存活比线性回归方程,即Gi/G0=A-P/10KE-CWH(t譵),被贮藏在低温种质库的小麦种子的实际发芽率和贮藏时间证明,是适合用于预测贮藏在低温种质库的小麦种子寿命的,尤其在预测发芽率时较预测贮藏时间有更高的准确性。     

香港次生林树种种子生理生态学特性的研究

１９８９～１９９１年在温室和野外测定了香港４０种次生林树木种类的种子寿命和发芽率．结果显示，在所测试的４０种天然林树种中，６０％的树种的种子寿命短于１年，仅有８个树种的种子寿命在１年以上．种子的寿命与种子在土壤中的发芽能力呈负相关的关系．种子发芽测定结果表明，大多数树种都可以在强光照条件（９５％的日光）下发芽，但３５％的测试树种不能在天然林下（０７％～２％的日光）发芽．最后从植物生理生态的角度，探讨种子特征与香港次生林区系发展及香港现有次生林的演替现状     

影响4类作物种子寿命的主要贮藏环境因素

为研究利用存活比、影响种子贮藏寿命和生活力的主要贮藏环境因子来预测高粱、苋属、甜荞麦和莴苣种子批的寿命和生活力,3个含水量水平的高粱和苋属的8个种子批被贮藏在20℃、30℃和40℃的贮藏温度下长达810 d。以概率回归和存活比线性回归方法,贮藏试验获得的高粱、苋属及文献报道的甜荞麦、莴苣种子批的发芽率和贮藏时间的成套数据,被用于估算不同种子批的平均贮藏寿命(p50)和种子死亡时间分布的标准差(σ),同时两种回归方程的拟合性也被比较;两种方法估算出的p50和σ则分别被用于对贮藏环境因子:贮藏温度(t)及其平方、种子含水量(m)及其对数(logm)以及t和m的交互作用(t×m和t×logm)作逐步回归分析,结果表明,用存活比来估算p50、σ是可行的,而且估算出的p50和σ较用概率估算的有统计学意义;贮藏温度和种子含水量的交互作用(t×m)是使4类作物种子快速丧失生活力,减少寿命的主要贮藏环境因子,包含这个因子和存活比的数学模型:G i/G0=A-p/10K-CWT(t×m),预测甜荞麦种子批的发芽率较V i=K i-p/10K-CWT(t×m)有更高的准确性;所以,建议用前者来预测初始发芽率是已知的种子的贮藏寿命和生活力,而用后者预测初始发芽率未被测定的种子的寿命和生活力。     

洋葱种子含水量与贮藏温度对其寿命的影响

不同含水量（MC7.1％～1.2％）的洋葱种子贮藏在35℃、室温、15℃和5℃条件下1～3年,适度超干处理能延长种子的贮藏寿命;种子的贮藏寿命与种子含水量和贮藏温度密切相关。种子贮藏的最适含水量随温度的改变而发生相应的变化,35℃时MC为3.4％;室温时为3.4％～4.5％;15℃时为4.5%～5.1％。MC≤2.2％不利于延长种子寿命。在室温自然条件下贮藏1～3年,适度超干种子（MC3.4％）内MDA和H2O2含量、O－*2产生速率和LOX活性明显地低于未超干种子（MC7.1％）和高度超干种子（MC1.2％）,而抗氧化酶AsA-POD、CAT和SOD的活性显著地高于未超干种子（MC7.1％）和高度超干种子（MC1.2％）。据此认为对脂质过氧化的抑制作用是适度超干种子耐贮藏的生理原因之一。     

植物遗传资源的种子基因库保存

一个物种的灭绝是与其受生物因子和非生物因子的威胁程度相关的。随着物种的加速绝灭,保护生物多样性受到广泛地关注。保护生物多样性的最有效的生物技术之一是建立种子基因库,进行迁地保护。种子库理想的贮藏条件主要取决于种子含水量、贮藏环境(如温度和湿度)和贮存种子的容器。进行种子贮藏,了解种子生命力和活力的影响因子的作用机理是十分重要和必要的。除了种子自身的生理特征外,种子的贮藏寿命与种子成熟度、收获技术、加工处理方法也是息息相关的。即使在最适的库存条件下,种子也会随时间发生劣变。因此,必须根据种子特定的贮藏行为,加以考虑影响种子存活的3个主要方面(贮藏环境、贮藏期和植物种类)而选择有效的贮藏方案。本文试图讨论种子贮藏生理的几个重要方面及其需解决的技术问题,以便更好地通过种子基因库,长期有效地保存植物种质资源。     

洋葱种子含水量与贮藏温度对其寿命的影响

不同含水量（MC 7．1％－1．2）的洋葱种子贮藏在35℃、室温、15℃和5℃条件下1－3年,适度超于处理能延长种子的贮藏寿命;种子的贮藏寿命与种子含水量和贮藏温度密切相关。种子贮藏的最适含水量随温度的改变而发生相应的变化,35℃时MC为3．4％;室温时为3．4％－3．5％;15℃时为4．5％－5．1％。MC≤2．2％不利于延长种子寿命。在室温自然条件下贮藏1－3年,适度超干种子（MC3．4％）内MDA和H2O2含量、O2^-产生速率和LOX活性明显地低于未超干种子（MC7．1％）和高度超干种子（MC1．2％）,而抗氧化酶AsA-POD 、CAT和SOD的活性显著地高于未超干种子（MC7．1％）和高度超干种子（MC1．2％）。据此认为对脂质过氧化的抑制作用是适度超干种子耐贮藏的生理原因之一。     

荒漠木本植物种子萌发研究进展

总结了荒漠木本植物种子萌发研究方法、影响种子萌发的自身因素和外部生态因子.荒漠木本植物种子萌发研究方法大多局限于室内培养箱和气候室模拟发芽法.种子休眠是影响种子萌发的重要生理因素;荒漠木本植物种子大小、质量和色泽与种子成熟度及活力密切相关;种皮通透性差是种子萌发的重要障碍,一般通过磨砺、削切、预冷、化学试剂处理等降低或消除其影响;种子含水量与贮藏寿命和吸胀力密切相关.适宜温度是荒漠木本植物种子萌发的先决条件,变温促进萌发;水分是种子萌发的制约条件;光照并非是大多数荒漠木本植物种子萌发的必要条件;沙埋通过综合调控光、温和水而影响种子萌发;盐分胁迫显著抑制种子萌发.随着研究不断深入,应加强多因素影响及机理方面的研究.     

Environmental impact on age-related dynamics of karyotypical instability in plants

The dynamics of karyotypical instability of Allium fistulosum L. (Welsh onion) during aging of genetically homogenous seeds from plants grown in three different areas was studied. We analyzed the frequency of anaphase cells with chromosomal aberrations "damage", as a number of chromosomal aberrations per cell with aberrations, and germinating capacity, as an indicator of the 'toxic' influence of age. The seeds' aging was accompanied by an increase in karyotypical instability (increasing frequency of anaphases with aberrations) and with certain changes in the spectrum of chromosome aberrations. The clearest distinctions between old and young seeds were found for the frequency of anaphase cells with chromosome aberrations. The general level of karyotypical instability positively correlates with the age of the seeds. The regression coefficient (b) corresponds to the general tendency of karyotypical instability during seeds' senescence under storage. For 'good' (A), 'normal' (B) and 'bad' (C) conditions, the coefficients (b's) are b(A)=0.22, b(B)=0.46 and b(C)=0.84 (p<0.05 for C, and p<0.001 for A and B). It was found that different ecological conditions of plant vegetation strongly influence age-related dynamics of chromosomal instability in the seeds obtained from these plants. Possible mechanisms of the transgenerational impact of this effect are discussed.     

Chemopreventive activities of Trigonella foenum graecum (Fenugreek) against breast cancer

Cancer is the second leading cause of death worldwide. Conventional therapies cause serious side effects and, at best, merely extend the patient's lifespan by a few years. Cancer control may therefore benefit from the potential that resides in alternative therapies. There is thus an increasing demand to utilize alternative concepts or approaches to the prevention of cancer. In this report, we show a potential protective effect of Fenugreek seeds against 7,12-dimethylbenz(alpha)anthracene (DMBA)-induced breast cancer in rats. At 200 mg/kg b.wt., Fenugreek seeds' extract significantly inhibited the DMBA-induced mammary hyperplasia and decreased its incidence. Epidemiological studies also implicate apoptosis as a mechanism that might mediate the Fenugreek's anti-breast cancer protective effects. To our knowledge, this is the first study that suggests significant chemopreventive effects of Fenugreek seeds against breast cancer.     

氨基酸厂废水对植物种子萌发和幼苗生长影响的研究

水稻、大麦、油菜等种子在不同条件下的发芽试验,表明氨基酸厂废水对植物种子萌发存在明显的抑制作用,且这种抑制作用主要表现在出芽阶段生物化学代谢最旺盛的时期,发现淀粉性种子对废水的忍耐程度要低于油脂性种子,同时进行的植物幼苗试验显示,大麦土培时废水最适宜的浓度为１：１００－１：１５０（废水原液与清水体积之比,下同）,水稻砂培为１：１００。     

Storage and mobilization as antagonistic functional constraints on seed storage globulin evolution

When seeds germinate nearly all the proteins are degraded in senescing storage tissue cells. All these proteins act as amino acid reserves which are mobilized to nourish the seedling. Nevertheless, the major amount of the seeds' protein reserve consists of a few enzymatically inactive, abundant, genuine storage proteins. In their metabolism the conflicting processes of biosynthesis, protein turnover and breakdown, are temporally separated. No degradation of correctly formed storage proteins was observed at the time of synthesis and accumulation during seed maturation. Breakdown takes place after a (long) period of rest when seeds germinate and seedlings start growing. At that time genuine storage proteins are no longer synthesized. Genuine storage proteins have evolved structural features permitting controlled temporal patterns of protection and proteolysis. The acquisition of inserted sequence stretches as sites accessible to limited proteolysis played a key role in the evolution of this control system and happened in coevolution of genuine storage proteins with specific proteinases. This can be deduced from the results of current research on the mechanisms of limited and unlimited proteolysis of storage globulins and on storage globulin evolution. The evolved system of controlled structure-function interplay between storage globulins and proteinases is part of a syndrome that, in addition, comprises differential compartmentation and gene expression of storage proteins and proteinases for controlling the total spatial and temporal patterns of globulin storage and mobilization in maturing and germinating seeds.     

金线兰种子萌发及其原球茎的增殖培养

研究了影响金线兰种子非共生萌发的因素,并应用正交试验研究基本培养基、6-BA、ZT、NAA四种因素对原球茎增殖的作用。结果表明:授粉类型对金线兰种子非共生萌发影响较大,异株异花、同株异花以及同株同花授粉所得的种子的萌发率分别为78.53%、69.62%、39.87%;蒴果成熟度以生长150d为宜,采收后萌发率可达78.59%;冷藏影响种子的活力,种子的萌发率随冷藏时间的延长而降低;使用次氯酸钠浸泡后的种子与对照相比,其萌发率无明显差异;NAA对原球茎增殖作用显著,适宜于原球茎增殖的培养基为1/2MS+ZT0.5mg/L+NAA1.0mg/L。     

Hydrogen Sulfide Promotes Wheat Seed Germination and Alleviates Oxidative Damage against Copper Stress

With the enhancement of copper (Cu) stress, the germination percentage of wheat seeds decreased gradually. Pretreatment with sodium hydrosulfide (NaHS), hydrogen sulfide (H2S) donor alleviated the inhibitory effect of Cu stress in a dose-dependent manner; whereas little visible symptom was observed in germinating seeds and radicle tips cultured in NaHs solutions. It was verified that H2S or HS- rather than other sulfur-containing components derived from NaHs attribute to the potential role in promoting seed germination against Cu stress. Further studies showed that NaHS could promote amylase and esterase activities, reduce Cu-induced disturbance of plasma membrane integrity in the radicle tips, and sustain lower levels of malondialdehyde and H2O2 in germinating seeds. Furthermore, NaHs pretreatment increased activities of superoxide dismutase and catalase and decreased that of lipoxygenase, but showed no significant effect on ascorbate peroxidase. Alternatively, NaHs prevented uptake of Cu and promoted the accumulation of free amino acids in seeds exposed to Cu. In addition, a rapid accumulation of endogenous H2S in seeds was observed at the early stags of germination, and higher level of H2S in NaHS-pretreated seeds. These data indicated that H2S was involved in the mechanism of germinating seeds' responses to Cu stress.     

Purification and partial characterization of another form of the antiviral protein from the seeds of Phytolacca americana L. (pokeweed).

1. The pokeweed antiviral protein, previously identified in two forms (PAP and PAP II) in the leaves of Phytolacca americana (pokeweed) [Obrig. Irvin & Hardesty (1973) Arch. Biochem. Biophys. 155, 278-289; Irvin, Kelly & Robertus (1980) Arch. Biochem. Biophys. 200, 418-425] is a protein that prevents replication of several viruses and inactivates ribosomes, thus inhibiting protein synthesis. 2. PAP is present in several forms in the seeds of pokeweed. One of them, which we propose to call 'pokeweed antiviral protein from seeds' (PAP-S) was purified in high yield (180 mg per 100 g of seeds) by chromatography on CM-cellulose, has mol.wt. 30 000, and is similar to, but not identical with. PAP and PAP II. 3. PAP-S inhibits protein synthesis in a rabbit reticulocyte lysate with an ID50 (concentration giving 50% inhibition) of 1.1 ng/ml (3.6 x 10(-11) M), but has much less effect on protein synthesis by whole cells, with an ID50 of 1 mg/ml (3.3 x 10(-5) M), and inhibits replication of herpes simplex virus type 1.     

Seedling growth of four fire-following Mediterranean plant species deprived of single mineral nutrients

1. Anthyllis vulneraria, Cistus creticus, Hippocrepis unisiliquosa and Pinus brutia are frequent post-fire colonizers whose seedlings are subjected to the mineral conditions imposed by ash in the early stages of growth. We test the hypothesis that the effective internal supply of mineral elements in the seeds of these species may complement the external availability of specific nutrients.
2. Newly germinated seedlings were grown in nutrient solutions, each deficient in one of the following elements: nitrogen, phosphorus or potassium. Control treatments consisted of full nutrients and distilled water. Seedling growth was monitored over 12weeks. The final dry masses of the seedlings were taken as a measure of the availability of each element from the seeds' own stored reserves.
3. For the two legume species nitrogen was the most limiting element followed by phosphorus. Potassium deficiency had no effect on the final legume dry biomass. For Cistus, the order was nitrogen followed by potassium, while phosphorus deprivation had no effect on growth during the 12weeks of the experiment. Deprivation of single minerals had no significant effect on seedling growth of Pinus over the same period. The two legumes and Cistus when denied nitrogen had relatively greater relative root ratios than control plants.
4. The relative seedling requirements of each species for early external supplies of the various nutrients for establishment in the field are discussed with reference to the adaptation of the four species to post-fire regeneration.     

Mobilization of Minerals to Developing Seeds of Legumes

The mineral nutrition of fruiting plants of Pisum sativum L.,Lupinus albus L. and Lupinus angustifolius L. is examined insand cultures supplying adequate and balanced amounts of essentialnutrients. Changes in content of specific minerals in leaves,pods, seed coat, and embryo are described. P, N and Zn tendto increase precociously in an organ relative to dry matteraccumulation, other elements more or less parallel with (K,Mn, Cu, Mg and Fe) or significantly behind (Ca and Na) dry weightincrease. Some 60–90 per cent of the N, P and K is lostfrom the leaf, pod and seed coat during senescence, versus 20–60per cent of the Mg, Zn, Mn, Fe and Cu and less than 20 per centof the Na and Ca. Mobilization returns from pods are estimatedto provide 4–39 per cent of the seeds' accumulations ofspecific minerals, compared with 4–27 per cent for testatransfer to the embryo. Endosperm minerals are of only minorsignificance in embryo nutrition. Comparisons of the mineral balance of plant parts of Lupinusspp. with that of stem xylem sap and fruit tip phloem sap supportthe view that leaves and pod are principal recipients of xylem-borneminerals and that export from these organs via phloem is themajor source of minerals to the seeds. Endosperm and embryodiffer substantially in mineral compostition from phloem sap,suggesting that selective uptake occurs from the translocationstream during seed development. Considerable differences are observed between species in mineralcomposition of plant organs and in the effectiveness of transferof specific minerals to the seeds Differences between speciesrelate principally to Ca, Na and certain trace elements.     

Gap colonization in the Patagonian semidesert: seed bank and diaspore morphology

We report work on a cold, windy South American steppe dominated by tussock grasses and shrubs of small stature that, together, cover only half of the soil surface. Our objective was to find out why seedlings and juveniles of these dominant species are generally absent from the bare or poorly-populated spots (gaps) that exist between established individuals. We hypothesized that matrix-forming species fail to colonize gaps because of a lack of properly-placed seeds, contained in diaspores which because of their morphology are blown away from gaps that otherwise would constitute safe sites for recruitment. We evaluated diaspore size and wing loading (weight:area ratio) for all common species in the community, collected seed-bank samples in different occasions and microsites, and performed detailed field observations for one gap-dwelling species during several years. We found that: 1) Seeds of the dominant, matrix-forming species are uncommon in the soil bank of the center of the gaps between established vegetation. 2) Seeds of the dominant species are more abundant towards the edges of the gaps than at their center. 3) Diaspores of those species present in the seed bank of the gaps are smaller than diaspores of absent species; contrary to expectations, not all gap-dwelling species had larger diaspore wing loading than non-gap species. 4) Seeds and adult densities of the most common gap species (the annual Camissonia dentata ), were correlated between them and across subsequent years. We conclude that it is not an overall shortage of seeds that precludes the dominant species from becoming established in the gaps, but rather the seeds' uneven spatial distribution. We further argue that gaps would be suitable sites for recruitment, but large diaspore size makes seeds of the dominant species to be blown away by the strong westerly winds.