【作者】 田雨；

【导师】 周道玮；

【作者基本信息】 东北师范大学 ， 生态学， 2011， 博士

【摘要】 世界范围内土壤盐渍化问题日趋严重。氯化钠是最广泛分布的可溶性盐,严重影响着植物生长和作物产量。种子发芽和幼苗阶段是植物生活史的关键时期。理解该阶段的耐盐特征和机制,为改善植物耐盐性提供依据和理论基础。在过去的几十年中,植物育种者在寻求一种可靠且成本低的耐盐筛选方法以提高耐盐作物育种的效率。本研究以NaCl单盐胁迫为主要胁迫因子,研究了种子发芽在逆境下的响应,并探讨了几种有潜力的提高种质抗逆性方法,主要目的是研究温-盐,温-旱交互作用下种子发芽特征,探讨盐的渗透离子双重作用对种子发芽阶段的影响。描述不同盐胁迫持续时间对种子发芽复萌的影响,探讨植物在种子阶段可能的耐盐适应机制;试验一种能够提高种子抗逆性的方法——种子引发,包括引发剂的筛选,旨在选出种子引发效果最好、最便捷的引发剂,借助积温模型和水势模型探讨引发对种子发芽的作用机制,并模拟田间出土;探索早期幼苗阶段筛选大量耐盐种质的方法;研究模式物种的耐盐机制,为基因工作提供理论基础和资源。本文的主要结论是温度和盐分,温度和干旱交互影响着种子发芽表现。高温下盐的胁迫作用最大;低渗透势下胁迫能促进种子发芽;多数情况下盐的渗透效应起主导作用。高盐胁迫对种子发芽复萌存在积极或消极的作用。短期的胁迫对种子发芽有促进作用,即盐引发;长期胁迫可能导致种子死亡或进入次级休眠。短期胁迫后在低盐溶液中复萌不受影响;长期胁迫后低盐中可能不能恢复萌发。4种引发剂加速了玉米种子吸水;吸湿回干处理下10%PEG对幼苗生物量积累的效果最佳;综合产量因素来看,水是最便捷廉价的引发剂。引发处理降低了种子发芽的积温需求;引发效应在早春温度较低的条件下显示出最大作用;种子引发后,幼苗根系提前发育,意味着幼苗有更强的耐旱性。引发处理降低了种子发芽的水势常数,这种效应在低温下更显著,即环境水势一定的情况下,引发后的种子能够发芽的时间缩短,直接指示了种子抗旱性提高。抗逆育种工程需要快速且有指向性的筛选大量种质的方法,本研究结果指出早期幼苗(7日龄)的胚根长度是对盐胁迫最敏感的指标,可用于筛选有耐盐差异的大量基因型。方法简单,用时短。筛选前需要摸索合适的筛选浓度,该浓度因物种而异。就苜蓿属植物而言200mMNaCl可作为筛选的标准。根再生法筛选耐盐种质适用于物种种间和种内的筛选,水培法筛选七天,快速有效。藜麦已证实具有粮食价值,也是一种很好的模式物种,可以用于耐盐植物的基因和生理学研究。当藜麦在高水平盐胁迫(400mM)时,植株显示出一系列形态和生理上的变化,这些变化包括地上Na+量增加,优先积累在老叶片中;进入木质部的K+显著增加,进而导致叶片组织中K+积累;发育中的幼叶有更好地渗透保护以抵抗氧化胁迫;单位面积上气孔数的减少以及伴随的平铺细胞减少,气孔导度降低。这表示双子叶盐生植物为了抵御盐分的双重影响(渗透胁迫和离子毒害)产生的机制和对策。更多还原

【Abstract】 Soil salinization is a serious worldwide problem and getting more and more serious. More than 800 million hectares of land throughout the world are salt affected. NaCl is the most soluble and widespread salt, which is limits plant gowth and yield greatly. Seed germination and seedling growth is the crucial phases in plant life cycle. Understanding the germination characteristic and mechanism of salt tolerance at this phase will provide theoretical basis for improving plant salt tolerance. In the past few decades, plant breeders in seeking a reliable and low-cost screening method to improve plant salt tolerance.This study used NaCl as the main stress factor, surveyed the response of seed germination under stress condition; and probed into several potential methods for improving germplasm salt resistance. We described the effects of salinity and temperature on seed germination, and discussed the double effects of salinity, viz osmotic and ionic on germination. We determined how salinity, exposure time and low salt concentration influence seed germination recovery and to get a whole knowledge seed germination strategy under constant changes’edaphic condition. We tested pre-sowing seed treatment as a shotgun approach to impove germination ability——seed priming,including selecting reagents which most effectively and low-cost; modeling the priming effect by thermal time model and hydrotime model and simulated emergence on the field. We also explored the method for screening salt tolerance germplasm at early seedlings. We researched on model species to explore the mechanism of salt tolerance, which could provide theoretical basis for genetic engineering.We obtained the important results and conclusions as follows.Temperature and salinity and their interaction influenced seed germination performance. High temperatures inhibited germination severly; Low water potential could improve germination; in most case, the osmotic effect of salinity plays a role. The increased salinity‘pre-treatment’raised the recovery percentage. As the exposure duration extended, the recovery percentage obviously decreased. Seed could recovery under non- or slight NaCl solutions, however, after seeds emerged in 400mM NaCl for 20d, the recovery ability under 100mM was remarkable lower than in 0 and 50mM NaCl. It is concluded that exposure to hyper-saline condition for short-time can stimulate germination in this species, and prolonged time can inhibit germination recovery.The four priming regents all accelerated seed imbibition; 10%PEG is the best osmoticum for seedling and biomass is highest; Water as the priming regent was low-cost and more convenience, and also took account of seed yield.Priming decreased the thermal requirement of all the tested crops; The simulated priming effect was maximized during the cooler conditions in early spring; The root system of primed seeds developed in advanced, and indicated that the seedlings were more tolerant to drought.Priming decreased hydrotime constant, the priming effect more significant at low temperature.If the environmental water potential fixed, then the primed seed could germinate earlier. This gave indirect evidence that priming can improve the drought tolerance in seed.The results indicated that the radicle of early seedlings (7 day age) is the most sensitive organ to salt stress, and can be used for screening a large number of salt tolerance genotypes. The method is simple and save time. The Root re-growth method could be applicable to screening salt tolerance germplasm inter- and intra- species.Quinoa already proven value as a seed crop for human consumption makes quinoa a prime candidate for becoming a‘model’species for the elucidation of the genetics and physiology of salt tolerance in plants.When quinoa plants are exposed to high levels of NaCl (400 mM), the plants show a suite of morphological and physiological changes that are indicative of mechanisms and strategies used by dicotyledonous halophytes to combat the dual affects of alinity, these being osmotic stress and ion toxicity. These changes include an increased amounts of Na+ in the shoot , with preferential accumulation of Na+ in old versus young leaves; a significant increase in K+ loading into the xylem with a resulting increased accumulation of K+ in leaf tissues; better osmoprotection of young developing leaves against associated oxidative stress; a significant reduction in the number of stomata per leaf area, as well as a concomitant decrease in the number of pavement cells; and a reduction in measured stomatal conductance that was less pronounced in salt tolerant varieties. Collectively, these traits contribute to the remarkable salinity tolerance of quinoa; a species that can complete its life cycle in NaCl concentrations equivalent of seawater.更多还原