胀果甘草种子萌发对干旱胁迫的生理响应

为探讨胀果甘草种子萌发对干旱胁迫的生理生化适应机制,以聚乙二醇(PEG)-6000模拟干旱胁迫,分析了胀果甘草(Glycyrrhiza inflata)种子萌发过程中发芽率(GR)、丙二醛(MDA)及游离脯氨酸(Pro)、可溶性糖(SS)含量和超氧化物歧化酶(SOD)、过氧化物酶(POD)活性的动态变化规律。结果显示,水势为-0.1MPa时,GR达到100%,之后随着干旱胁迫增强而显著降低(P0.05);MDA、Pro含量及SOD、POD活性都表现出水势≥-0.2MPa时增加和-1.4MPa≤水势-0.2MPa时减少的明显趋势(P0.05),这4个指标两两之间的相关关系均达到显著水平(P0.05);而干旱胁迫增强使SS含量显著增加(P0.05)。     

云锦杜鹃种子萌发及对干旱胁迫的响应

以不同渗透势的PEG-6000溶液模拟干旱胁迫条件, 研究云锦杜鹃种子的萌发、幼苗生长和累积吸水率对干旱胁迫的响应。结果显示：种子于第14 d开始萌发,萌发期为8 d,总萌发率为45.5%±1.7%。在渗透势为-0.3～-0.6 MPa的溶液中, 种子的累计吸水率在第5 d就超过对照(蒸馏水中), 种子的萌发和幼苗的生长也优于对照, 说明云锦杜鹃种子不适合过于湿润的土壤环境中萌发。但溶液的渗透势≥-0.9 MPa时, 种子的吸水减缓、萌发率下降, 同时幼苗的生长也慢, 而当渗透势≥-1.8 MPa时, 种子不能充分吸涨、萌发, 说明云锦杜鹃种子对干旱胁迫比较敏感。另外, 经PEG溶液浸种2天后移入蒸馏水中,萌发率均有一定程度的提高, 其中经-0.3～-1.5 MPa的PEG溶液浸种后, 萌发率显著高于对照。提示用一定浓度范围的PEG溶液浸种可使休眠种子活化, 提高种子繁育的效率。     

逆境条件下小麦种子活力与种子萌发相关酶活性及其基因表达的关系

分析不同基因型小麦品种逆境萌发过程中种子萌发相关酶活性及基因表达差异,明确在逆境条件下,种子活力与种子萌发相关酶活性及基因表达量的关系.通过标准发芽试验和逆境(冷浸、人工老化、干旱胁迫)发芽试验,测定4个小麦品种种子活力、萌发过程中可溶性总糖和可溶性蛋白含量、α-淀粉酶活性、半胱氨酸蛋白酶活性及相关基因表达量.结果表明:干旱、人工老化和冷浸胁迫3种逆境对种子活力都有一定影响.不同萌发条件下,可溶性总糖含量呈现先小幅度升高后小幅度降低再迅速升高的趋势;而可溶性蛋白含量随着萌发时间的延长呈现逐渐下降的趋势.α-淀粉酶活性整体呈现逐渐升高的趋势,但在冷浸胁迫处理后,豫农949和轮选061的α-淀粉酶活性在萌发60 h后出现下降.半胱氨酸蛋白酶活性整体呈先降低后升高的趋势,但在干旱胁迫条件下,豫农949、豫麦49-198和轮选061的半胱氨酸蛋白酶活性呈现先升高后降低再升高的趋势.不同逆境萌发条件下,α-AMY(α-淀粉酶基因)表达量整体呈先上升后下降的趋势.冷浸胁迫处理后,轮选061的α-AMY表达量高于对照,在其他逆境萌发条件下,4个品种的α-AMY表达量均低于对照;人工老化处理后,长4738的CP(半胱氨酸蛋白酶基因)表达量与对照差异不显著,在其他逆境萌发条件下,4个品种的CP表达量均高于对照.种子萌发期间,不同萌发条件下α-淀粉酶和半胱氨酸蛋白酶活性与其基因表达并没有直接关系,α-淀粉酶活性与可溶性总糖含量达到显著正相关,半胱氨酸蛋白酶活性与可溶性蛋白含量的相关性不显著.在标准发芽条件下,α-淀粉酶活性与活力指数呈显著正相关,而在逆境萌发过程中,其相关性不显著.冷浸胁迫处理后,半胱氨酸蛋白酶活性与活力指数呈显著正相关,但在标准发芽、干旱胁迫、人工老化处理后,其相关性不显著.     

几种旱生灌木种子萌发对干旱胁迫的响应

以不同渗透势的PEG(6 0 0 0 )溶液 (- 0 .3～ - 2 .7MPa)为模拟干旱胁迫条件 ,研究了柠条 (Caraganakorshinskii)、花棒 (Hedysarumscoparium)和白沙蒿 (Artemisiasphaerocephala)种子发芽、幼苗生长和累积吸水率对干旱胁迫的响应 ,讨论了参试种子发芽特性、初生根长度与幼苗建植成活率的关系 .结果表明 ,干旱胁迫下柠条发芽率最高 ,其次为花棒 ,白沙蒿最低 . - 0 .3～ - 0 .6MPa渗透势下白沙蒿发芽 10d的初生根长度显著大于花棒和柠条 (P <0 .0 5 ) ,三者的测量值依次为 7.9、4 .5和 3.1cm .干旱胁迫条件下参试种子发芽率与种子 72h累积吸水率均呈极显著的正相关 (P <0 .0 1) .     

种子植物对中波紫外辐射胁迫的响应研究进展

臭氧层的破坏导致到达地表的中波紫外辐射(UV-B)增加。增强的UV-B对植物产生不同程度的胁迫作用。综合论述了近些年来有关种子植物对UV-B胁迫响应的研究进展。对UV-B敏感的种子植物经UV-B处理,外部形态表现为植物变矮、叶面积减小、茎缩短等;内部结构表现为叶绿体结构失去完整性、叶肉面积减小等。种子植物受UV-B影响的主要部位包括光合器官、遗传物质、蛋白质等。为了减轻UV-B的伤害,种子植物形成了一系列的保护机制,包括表皮结构对UV-B的散射、反射,叶片厚度的增加、UV-B吸收物质的积累、受损DNA的修复、自由基的去除。此外,UV-B与干旱、增强C02具有互作效应。增强的UV-B对木本植物、生态系统等方面的影响研究应加以重视。     

Approaches and challenges to engineering seed phytate and total phosphorus

About 75% of seed total phosphorus (P) is found in a single compound, phytic acid (myo-inositol-1,2,3,4,5,6-hexakisphosphate or InsP₆). Phytic acid is not efficiently utilized by monogastric animals (poultry, swine, fish), which creates phosphorus management and environmental impact problems in animal production. Phytic acid also functions as an antinutrient when consumed in human and animal diets. These problems can be addressed via feed or food supplementation with P and other minerals or phytase, or more efficiently and sustainably at their source by crop breeding or bioengineering of low-phytic acid/high-available P crops. However, since phytic acid and its synthetic pathways are central to a number of metabolic, developmental and signaling pathways important to plant function and productivity, low-phytate can translate into low-yield or stress susceptibility. The biological functions of phytic acid and identification of genetic resources and strategies useful in engineering high-yielding, stress-tolerant low-phytate germplasm will be reviewed here. One promising approach that can avoid undesirable outcomes due to impacts on phytic acid metabolism is to engineer “high-phytase” seeds. In contrast to the issue of seed phytic acid, there has been relatively little interest in seed total P as a trait of agricultural importance. However, seed total P is very important to the long-term goal of sustainable and environmentally friendly agricultural production. Certain low-phytate genotypes are also “low-total P”, which might represent the ideal seed P trait for nearly all end-uses, including uses in ruminant and non-ruminant feeds and in biofuels production. Future research directions will include screening for additional genetic resources such as seed total P mutants.     

Aquaporins influence seed dormancy and germination in response to stress

Aquaporins influence water flow in plants, yet little is known of their involvement in the water‐driven process of seed germination. We therefore investigated their role in seeds in the laboratory and under field and global warming conditions. We mapped the expression of tonoplast intrinsic proteins (TIPs) during dormancy cycling and during germination under normal and water stress conditions. We found that the two key tonoplast aquaporins, TIP3;1 and TIP3;2, which have previously been implicated in water or solute transport, respectively, act antagonistically to modulate the response to abscisic acid, with TIP3;1 being a positive and TIP3;2 a negative regulator. A third isoform, TIP4;1, which is normally expressed upon completion of germination, was found to play an earlier role during water stress. Seed TIPs also contribute to the regulation of depth of primary dormancy and differences in the induction of secondary dormancy during dormancy cycling. Protein and gene expression during annual cycling under field conditions and a global warming scenario further illustrate this role. We propose that the different responses of the seed TIP contribute to mechanisms that influence dormancy status and the timing of germination under variable soil conditions.     

黑果枸杞种子萌发及幼苗生长对盐胁迫的响应

研究不同浓度(0、1、2、3、6、9、14、18g.L-1)的盐溶液(NaCl、MgSO4、盐渍土壤)对河西走廊中部荒漠边缘的黑果枸杞种子吸胀、萌发和幼苗生长的影响,并观察胁迫解除后种子的反应。结果表明:黑果枸杞种子吸胀速率随NaCl、MgSO4和土壤溶液浓度的增大呈先升后降的趋势,吸水速度随胁迫时间的延长而减慢;种子萌发率随3种盐浓度的增大而降低,盐胁迫解除后种子仍具有较高的萌发率;发芽指数、活力指数、根长、下胚轴随3种盐浓度的增大而降低或先升后降,根轴比随盐胁迫的增强先升后降;随3种盐浓度的增大,种苗损害率增大,3种盐的胁迫效应依次NaCl>MgSO4>盐渍土壤溶液。黑果枸杞种子萌发和幼苗生长对NaCl胁迫较为敏感,其耐受的临界阈值是6g.L-1;种子萌发能耐受较高浓度的MgSO4的胁迫,幼苗生长对MgSO4胁迫较敏感,其耐受的临界阈值是9g.L-1;种子萌发和幼苗生长对生境盐渍土壤具有较强的耐受能力和适应性。     

Evolution and ecology of seed internal morphology in relation to germination characteristics in Amaranthaceae

Background and AimsInternal seed morphological traits such as embryo characteristics and nutritive tissue can vary considerably within a plant lineage. These traits play a prominent role in germination processes and the success of seedling establishment, and are therefore under high selective pressure, especially in environments hostile to seedlings, such as arid, saline or highly dynamic habitats. We investigated the relationships of seed internal morphology and germination characteristics of 84 species of Amaranthaceae s.l., a family with numerous lineages that have adapted to stressful growing conditions.MethodsWe used seed cross-sections to assess embryo type and the ratios of embryo to seed surface and radicle to cotyledon length. Furthermore, seed mass, mean time to germination, habitat preferences and further plant traits such as C₃ or C₄ photosynthesis and life form were compiled for each species. Data were analysed using phylogenetic comparative methods.Key resultsWe found embryo type (λ = 1), log seed mass (λ = 0.86) and the ratio of embryo to seed size (λ = 0.78) to be evolutionarily stable, with an annular embryo as ancestral in the family. Linked to shifts to the three derived embryos types (spiral, horseshoe-shaped and curved) is an increase in the ratio of root to cotyledon length and a reduction of nutritive tissue. We observed stabilizing selection towards seeds with relatively large embryos with longer radicles and less nutritive tissue that are able to germinate faster, especially in lineages with C₄ photosynthesis and/or salt tolerance.ConclusionsWe conclude that the evolutionary shift of nutrient storage from perisperm to embryo provides an ecological advantage in extreme environments, because it enables faster germination and seedling establishment. Furthermore, the evolutionary shift towards a higher ratio of root to cotyledon length especially in small-seeded Amaranthaceae growing in saline habitats can provide an ecological advantage for fast seedling establishment.     

桔梗种子萌发对低温、干旱及互作胁迫的响应

以药用植物桔梗种子为材料,研究了低温、干旱及其互作对种子萌发和幼苗生长的影响,旨在探索在春寒干旱条件下其种子萌发对策及生态适应性,为桔梗野生种群恢复及人工栽培群体构建提供依据.结果表明,温度、干旱及其互作对桔梗种子萌发和幼苗生长均有显著影响.0-10％ PEG水分条件下,在变温10/20℃及恒温15-25℃下桔梗种子能够良好萌发(10％ PEG、20℃除外),而15％ PEG可显著抑制萌发.低温(10℃)下种子萌发始时间延迟,发芽率降低.随干旱胁迫程度的增加,10℃发芽率呈先升后降趋势,而其它温度下,发芽率和发芽指数均呈下降趋势.随温度的降低,幼苗根长、茎长及鲜重均呈下降趋势,且幼根生长对温度变化更为敏感.     

铬胁迫下不同品种玉米种子和幼苗的反应及其与铬积累的关系

研究了铬胁迫对玉米(6个品种)种子萌发初期一些生理生态特征的影响,及各种生理指标与幼苗铬积累量间的关系,结果表明,随铬处理浓度的加大而玉米种子萌发率逐渐降低,幼苗株高、根长、鲜物质量和干物质量均逐渐降低;脯氨酸、吸收铬量、可溶性蛋白质、超氧负离子、丙二醛含量逐渐上升,超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性则逐渐增加,根系活力和硝酸还原酶活性在不同品种玉米中差异较大;所有供试玉米品种中,丙二醛含量、CAT和SOD活性与幼苗铬积累量之间存在显著或极显著的正相关关系。不同玉米品种对Cr3+毒害的反应表现不同,存在品种间差异。     

土壤菲污染对两种草坪草种子萌发及其幼苗生长的影响

采用培养皿中的种子暴露试验方法,研究了2种城市绿化草种——多年生黑麦草和三叶草在不同多环芳烃菲污染浓度梯度和不同土壤改良方式下的种子萌发及其幼苗生长反应。结果表明:不同浓度菲污染对2个草种的发芽率和幼苗生长没有显著差异;除了低浓度胁迫下黑麦草处理外,所有处理的萌发指标大都随着菲胁迫浓度的提高而降低。此外,污染土壤的几种改良方式在一定程度上对草种的萌发及其幼苗生长有积极的作用。总的来说,表面活性剂和树木凋落物复合的改良作用效果要好于二者单独使用的效果。     

Effects of Neotyphodium fungi on Lolium multiflorum seed germination in relation to water availability

BACKGROUND AND AIMS: Temperate endophyte-infected (Neotyphodium sp.) grasses have been shown to exhibit an ecological advantage over endophyte-uninfected grasses under abiotic stressful conditions. It is predicted that endophyte-infected plant populations will display higher rates of germination and proportion of germinated seeds under limiting water conditions. METHODS: The hydrotime regression model was used to describe the effect of Neotyphodium endophyte on seed germination of Lolium multiflorum at different water potentials. Additionally, seed mortality after water stress exposure was estimated in endophyte-infected and -uninfected seeds. KEY RESULTS: Endophyte infection inhibited seed germination at all water potentials. The hydrotime model described satisfactorily the germination responses, and revealed that endophyte-free seeds exhibited higher rates of and final percentage germination, probably due to a lower base water potential compared with endophyte-infected seeds. However, Neotyphodium endophyte conferred a higher rate of survival in those seeds that remained ungerminated when exposed to highly water stress conditions. CONCLUSIONS: Changes produced by Neotyphodium endophyte in L. multiflorum seeds might affect fitness in particular ecological scenarios. For example, the presence of the endophyte may curtail seed germination when water is limiting, reducing the risk of seedling death. Conversely, endophyte-free seeds would display an enhanced germination, ensuring a more rapid seedling establishment if later water conditions do not restrict plant growth.     

Canola seed germination and seedling emergence from pre-hydrated and re-dried seeds subjected to salt and water stresses at low temperatures

Low soil temperatures and low water potentials reduce and delay the seed germination of canola (Brassica rapa L., B. napus L.) in western Canada. Germination is also very sensitive to the salinity effects of nitrogen fertiliser placed with the seed, especially when the seed bed is relatively dry. The effects of pre-hydration and re-drying treatment on canola (Brassica rapa L. cv. Tobin) seed germination and seedling emergence at 10°C subjected to either a water or salt stress were determined. Low water potentials, induced by polyethylene glycol (PEG 8000), low soil moisture, or high concentrations of salts, reduced both germination and seedling emergence, and increased the time to 50% germination and emergence of seeds at 10°C. At equal osmotic potentials, Na₂SO₄ was less inhibitory on low temperature germination than either NaCl or PEG, suggesting that the sulphate ion partially alleviated the inhibitory effects of low water potential. Solutions of NaCI produced more abnormal seedlings compared to Na₂SO₄, suggesting that NaCl was more toxic than Na₂SO₄ during seedling development. Pre-hydration and re-drying partially overcame the inhibitory effects of both low water potential and salts on seed germination and seedling emergence at 10°C. The seed treatment increased the germination rate in Petri dishes and seedling emergence from a sandy loam soil. Water potentials or soil water contents required to inhibit 50% germination or emergence at 10°C were lower for treated seeds compared to control seeds. Salt concentrations inhibiting 50% emergence were higher for treated seeds than control seeds. Neither treated nor control seeds produced seedlings which emerged if the soil water content was lower than 9% or when the soil was continuously irrigated with salt solutions of 100 mmol kg^-1 of NaCl or 50 mmol kg^-1 of Na₂SO₄. These results suggest that the pre-hydration and re-drying treatment did not lower the base water potentials at which seedling emergence could occur. Abnormal seedlings were observed in both treated and control seeds, particularly if the soil was watered with NaCl solutions; however, the seed treatment reduced the number of abnormal seedlings.     

Polypeptide markers for low temperature stress during seed germination in sunflower

Sunflower seeds behaved as chilling and freezing sensitive and also exhibited acclimation under low seed moisture content (< 1 %). At high seed moisture content (approx. 22 %) they tolerated chilling stress but failed to acclimate under freezing temperatures. Pre-imbibitional chilling (5 °C) or freezing (−5 or −10 °C) stress significantly enhanced total soluble protein (TSP) content. Chilling treatment after imbibition (in contrast to pre-imbibition) enhanced germination and this was accompanied by increase in 30, 24 and 21.9 kDa TSPs content (3 d after germination). Freezing at −5 and −10 °C suppressed seed germination and increased content of 78 and 56.2 kDa wall bound proteins. Chilling acclimation decreased 35.4, 33.9, 29.5, 23.4 and 21.4 kDa TSPs.     

种子预处理的作用机制研究进展

种子在自然和农业生态系统中起重要作用,其发芽成苗对于植物物种生存繁衍具有决定性作用,但由于老化、休眠及生境恶化等问题经常导致其活力严重受损,所以探索提高种子萌发质量的方法具有深远的经济和生态意义.基于国内外最新研究,种子预处理是使植物优质、多抗、高产最实用有效的方法.本文综述了近年来的种子预处理技术及其生理生化响应,包括基因表达、细胞学效应、酶系统活性、物质能量代谢、抗氧化机制及信号传导途径.从种子发芽的不同阶段和提高抗逆性角度,阐明各预处理方法的作用机制,总结了各方法在细胞学、分子水平上的研究瓶颈以及实践应用上存在的问题.目前研究多集中于生化改变和酶活性的局部响应,缺乏以生产实践为目的的整体系统研究,为此,本文提出了对种子预处理研究的展望,旨在为今后种质资源保存、发展绿色高效农业和生态环境建设提供科学参考.