【作者】 李晓宇；

【导师】 穆春生；

【作者基本信息】 东北师范大学 ， 生态学， 2010， 博士

【摘要】 土壤盐碱化给农业生产造成了严重的损失,是人类面临的生态危机之一。研究植物对盐碱胁迫的生理响应特点,提高作物和牧草的耐盐碱性和种子产量对改良和利用退化盐碱草地具有重要意义。植物激素是植物响应环境胁迫的信号转导的主要成员,当植物受到环境胁迫后,植物的生长和发育受到抑制,其激素含量会发生变化,相应的应用外源植物激素可缓解环境胁迫对植物的伤害。此外,植物激素也是成花的重要信号物质,植物激素如生长素(IAA)、脱落酸(ABA)和赤霉素(GA3)等对果树的成花具有一定的作用。针对东北盐碱土壤的现状,本论文以一年生粮食作物小麦和多年生牧草羊草为材料,分别研究了盐胁迫和碱胁迫对小麦幼苗和羊草幼苗生态和生理生长的影响,外源ABA在提高小麦耐盐碱性中的作用,以及外源植物激素对羊草有性生殖的影响。研究结果如下:(1)盐胁迫和碱胁迫均抑制了小麦幼苗的生长,且碱胁迫的伤害更大。两种胁迫下,小麦表现了不同的生理响应机制,在盐胁迫下,小麦大量积累Na+、Cl-等无机离子,及脯氨酸和可溶性糖等有机溶质,而未积累有机酸。在碱胁迫下,小麦积累大量Na+和有机酸、可溶性糖、脯氨酸,而未积累Cl-和H2PO4-等无机阴离子,有机酸和Cl-的积累是小麦对两种胁迫生理响应机制和适应对策的根本区别所在。通过对小麦茎叶和根中有机酸组分的测定,进一步证明苹果酸和柠檬酸是小麦幼苗抵御碱胁迫伤害的最主要有机酸成分;有机酸组分在茎叶和根中的含量和变化趋势不同,尽管茎叶中的有机酸含量明显高于根中,但碱胁迫后根中的增加量却明显大于茎叶中;随着碱度的增加,茎叶中的苹果酸和柠檬酸的含量显著增加,在根中则呈现先上升后下降的趋势,以上结果表明碱胁迫对小麦根系的危害程度明显大于茎叶,苹果酸和柠檬酸是小麦响应碱胁迫的主要有机酸组分。(2)叶面喷施ABA,可有效缓解盐胁迫和碱胁迫对小麦幼苗生长的伤害作用。小麦对盐胁迫和碱胁迫的生理响应机制不同,因此ABA在这些胁迫上的缓解机制也不同。盐胁迫下,ABA主要通过降低盐胁迫所引起的Na+的积累,提高K+/Na+和Ca2+/Na+的比值来达到缓解盐胁迫对小麦幼苗的伤害作用;碱胁迫下,ABA主要通过增加有机溶质的合成,(可溶性糖,柠檬酸和琥珀酸等)来响应碱胁迫,达到缓解碱胁迫对小麦幼苗的伤害作用,且低浓度ABA的缓解效果好于高浓度。(3)在一定浓度的盐胁迫和碱胁迫下,羊草幼苗的根生长并未受到影响,羊草幼苗的根茎生长受到的抑制作用高于其他器官。两种胁迫均使羊草的分蘖节和根茎所产生的芽数减少,且对根茎所产生的芽抑制作用更大,对羊草幼苗地上、地下生物量及地下芽数的影响中,都表现为高浓度碱胁迫具有显著抑制作用。两种胁迫下,羊草表现出不同的生理响应机制。在盐胁迫下,羊草积累以Na+和Cl-为主的无机离子,参与渗透及离子平衡调节,脯氨酸、可溶性糖和有机酸等有机溶质作为渗透溶质的调节作用较小;在所有器官中,根茎含有相对高的Na+和Cl-等盐离子及最低的硝酸根离子含量,根茎这种对盐离子的容纳及营养离子的贡献作用,减少了盐胁迫对其他器官生长的伤害,相对的保护了其他器官的正常生长。在碱胁迫下,羊草积累Na+的同时,更多的积累脯氨酸,可溶性糖和有机酸等有机溶质来参与碱胁迫下的渗透调节,此时根茎具有和盐胁迫下相似的生理响应特点,当碱胁迫浓度增高时,茎和叶内的Na+积累量增多,导致可溶性糖、脯氨酸和有机酸的合成也高于其他器官,茎和叶内毒害离子和有机溶质大量增加及幼苗生长的显著降低,表明高浓度的碱胁迫使羊草生长受到严重损害,物质代谢紊乱,此时有机溶质的合成是胁迫伤害的产物。(4)外源GA3显著增加了羊草生长季末的根茎顶芽、根茎节芽和根茎顶苗的数量,降低了根茎顶芽的内源IAA和ABA的含量,显著提高了翌年单位面积羊草的抽穗数和抽穗率,由此可以推出根茎顶芽及根茎顶苗是翌年羊草种群生殖枝的主要来源,内源IAA和ABA含量的下降是促进花芽分化的基础。外源IAA和KT(激动素,一种细胞分裂素)虽然也增加了根茎顶苗和根茎节苗的数量,但最终两种激素均未显著增加翌年羊草种群的抽穗数和抽穗率,其原因是外源IAA和KT均导致根茎顶芽内ABA含量增加,使得IAA/ABA的比值显著降低,抑制了羊草的花芽分化作用。(5)外源植物激素对羊草结实的影响与其施用浓度、施用时间和生理特性有关。返青期、分蘖期和拔节期分别喷施GA3、IAA及KT等三种激素对当年羊草的抽穗数与抽穗率均没有显著影响,这与羊草的幼穗分化时期和进程有关,此时期羊草已完成了幼穗分化。返青期施用GA3处理显著提高羊草的结实数、结实率、穗重和粒重;分蘖期施用GA3对有性繁殖数量性状无显著影响;拔节期喷施GA3显著增加羊草每穗小花数、结实数、穗重、粒重及种子产量,以上结果表明GA3对羊草的促进作用受施用时间和植物生长状态的影响,在羊草的返青后及拔节期应用GA3处理,不仅显著提高了结实率,而且大大降低了结实率的变异幅度,使羊草抽穗整齐,开花集中,授粉充分,结实率较高。返青期、分蘖期和拔节期施用IAA对羊草有性生殖数量性状均无显著促进作用。返青期和分蘖期喷施KT对羊草有性繁殖的影响相似,虽然未改变结实率,但是显著提高了羊草每穗结实数和粒重,对羊草的种子灌浆及发育具有明显的促进作用;拔节期喷施KT则显著地增加羊草每穗小花数、结实数、穗重、粒重及种子产量,不同KT浓度间无显著差异。更多还原

【Abstract】 Soil salinization and alkalization causes serious lesses in agricultural productivity and is one of ecological crisis that faces humans. In order to improve and use the degeneration and saline-alkalization grassland, it is important to study the physiological responses characteristics of plant to salt and alkali stresses, and to improve the salt and alkali tolerance, seed production of plant. Plant hormones are one of main signal transduction components of plant responding to environmental stresses. The hormones contents will change when plant growed in stress conditions. Application of exogenous hormones can alleviate the damage of environmental stress on plant. In addition, plant hormones are key factors in controlling the flower formation and reproductive growth of plants. In this paper, we used wheat and Leymus chinensis as the experiments materials, conducted the experiment to study the effects of salt and alkali stresses on wheat and L. chinensis seedlings; and alleviated function of ABA on both stresses; and application of plant hormones on improvement of sexual reproduction of L. chinensis. We got the conclusions as follows:(1)Salt and alkali stresses both inhibited the growth of wheat seedlings, and the adverse effects of alkali stress were higher than that of salt stress. Wheat had the different physiological responses mechanisms between salt and alkali stresses. Under salt stress, wheat significantly accumulated Na+ and simultaneously accumulated Cl-, soluble sugars and proline to keep osmotic and ionic balance. Under alkali stress, high pH enhanced Na+ accumulation and affected absorption of inorganic anions. To maintain ionic and osmotic balance, wheat greatly accumulated organic acids, soluble sugars and proline. The accumulation of Cl- and organic acids was the main difference of wheat in the physiological responses and adaptive mechanisms to salt and alkali stresses, respectively.Organic acids were the special components of wheat responding to alkali stress. We concluded that malate and citrate were the main OAs components of wheat seedling by determining the contents of organic acids components (OAs) in wheat shoots and roots, but the contents and increments of OAs between shoots and roots were different. All OAs components contents in shoots were higher than that in roots, but the increment in roots was higher than that in shoots. With increasing alkalinity, malate and citrate increased in shoots, but in roots they increased first then decreased after. It indicated that the injuries of alkali stress on roots were higher than that on shoots. Organic acids components played different roles in responding to alkali stress. Malate and citrate were the special OAs components of wheat responding to alkali stress.(2) Foliar application of ABA could alleviate the adverse effect of salt and alkali stresses on wheat seedlings. Because of the different responding mechanisms of wheat seedlings to salt and alkali stresses, the alleviation mechanisms of ABA on salt and alkali stresses were also different. ABA could decrease the accumulation of Na+ that caused by salt stress, and increase the ratio of K+/Na+ and Ca2+/Na+ to improve the salt resistance of wheat. Under alkali stress, application of ABA could increase the synthesis of organic solutes, such as soluble sugars, organic acids components contents in shoots to decrease the adverse effect of alkali stress on wheat. The lower concentration of ABA had the better mitigation effects than the higher one.(3) With certain concentration of salt and alkali stresses, the root growth of L. chinensis was not inhibited, and the inhibition of rhizome growth was higher than that of other organs. Both stresses decreased the buds number that produced from tillerings nodes and rhizomes, and the inhibition of the latter was higher. There was a significant inhibited effect of higher concentration of alkali stress on biomass of above- and under- ground and buds number, comparing with other stress concentration. L. chinensis indicated the different physiological responses mechanisms between salt and alkali stresses. Under salt stress, the inorganic ions such as Na+ and Cl- were the main osmotic ajustment substances of L. chinensis, the osmotic regulation of organic solutes such as soluble sugars, prolines and organic acids was little. Na+ and Cl- accumulated in L. chinensis distributed mainly in rhizome, and NO3- contents were the lowest in rhizome. The capacity of containing toxic ions in rhizomes protected the normal growth of other organs, and avoided adverse effect of salt stress on them. Under alkali stress, L. chinensis accumulated Na+, soluble sugars, proline, and organic acids to involve in the osmotic ajustment. The role of rhizome was similar to that of salt resistance. When the alkaline concentration increased, the contents of Na+, soluble sugar, proline, and organic acids in stems and leaves were increased sharply, which indicated that this concentration caused serious damage on L. chinensis, the metabolism of organic solutes was destroyed, the synthesis of which was the product of damage.(4) Exogenous GA3 significantly increased the number of apical rhizome buds, axillary rhizome buds and daughter shoots of apical rhizome at the end of growth season, and decreased endogenesis IAA and ABA contents, then significantly increased the heading number and heading percentage of unit area next year. We concluded that the apical rhizome buds and daughter shoots of apical rhizome were the main components of heading shoots next year. The decreases of endogenesis IAA and ABA were the foundation of inducing differentiation on reproductive buds. Although exogenous IAA and KT can increase the daughter shoots comed from apical rhizome and axillary rhizome, neither of them increased the heading number and heading percentage of L. chinensis population next year. The reason was that exogenous IAA and KT induced the increament of ABA contents, and decreased IAA/ABA, and had no significantly active effect on reproductive buds differentiation.(5) The regulation of plant hormone on growth and reproduction, was correlated with the treatment time, concentration and action mechanisms of plant hormone. There was no significant effect of GA3, IAA and KT on heading number and heading percentage when they were sprayed at the three stages. This was related to the process of spikelets differentiation. According to study of Zhang et al, L. chinensis had finished the spikelets differentiation in this time. On period of seedling establishment, GA3 treatment not only increased seed number, seeding percentage, weight of spikes and seeds, but also decreased CV of seed percentage, which optimized the heading, flower, pollination. But there was no significant effect of GA3 treatment on tillering stage. On jointing stage, GA3 could increasing the number of florets and seeds per spike significantly, and then increasing the weight of spike and seeds per spike and seed yield. So we concluded that GA3 accelerated the florets differentiation of L. chinensis. There was no positive effect of IAA on the traits of sexual reproduction number characters when it sprayed on period of seedling establishment, tillering stage and jointing stage. The effect of KT that sprayed on period of seedling establishment on seeding of L. chinensis was similar to that on tillering stage. They didn’t change the seeding percentage, but increased the seed numbers and spike weights, which played active function on seed filling and development. On jointing stage, KT could increase the number of florets and seeds per spike significantly, and then increase the weight of spike and seeds per spike and seed yield. But there was no difference between different concentration.更多还原