【作者】 郭瑞；

【导师】 杨允菲；

【作者基本信息】 东北师范大学 ， 生态学， 2010， 博士

【摘要】 盐碱胁迫已经成为世界性的环境问题,是限制中国乃至世界农业发展的重要因素。盐碱胁迫对植物的影响是多方面的,植物对盐碱胁迫所做出的适应性响应亦复杂多变,不同的植物种类可能会有完全不同的适应机制。因此,有必要总结和比较不同植物种类对盐碱胁迫的胁变反应和适应性调节机制。其中,禾本科植物是目前研究比较集中的种类,许多极端抗盐碱盐生植物也皆出自于此。为了总结和比较禾本科植物对耐盐碱胁迫的适应性调节机制,本文选择了典型的禾本科作物小麦（Triticum aestivum）和抗盐碱禾本科牧草:羊草（Leymus chinensis）、赖草（Leymus secalinus）和狗尾草（Setaria viridis）为试验材料,依据中国东北盐碱化草原盐碱化土壤既含中性盐又含碱性盐的特性,用中性盐NaCl、Na₂SO₄和碱性盐NaHCO₃、Na₂CO₃并以1:1的摩尔比分别混合模拟盐胁迫（30,60,90,120和150mM,摩尔比1:1的NaCl和Na2SO4）和碱胁迫（30,60,90,120和150mM,摩尔比1:1的NaHCO₃和Na₂CO₃）,并以此对这四种禾本科植物进行胁迫处理。通过测定萌发率、相对生长率RGR、含水量、光合参数、离子和溶质含量,分析渗透调节、离子平衡策略,进一步探讨盐碱胁迫对四种禾本科植物的胁迫效应以及它们对盐碱两种胁迫的适应机制。在盐胁迫下,低水势是抑制种子萌发的一个决定性的因素。结果表明同等盐度的碱胁迫（高pH）对小麦萌发的抑制作用大于盐胁迫。未萌发的种子可能是处在休眠状态来摆脱恶劣的环境影响。碱胁迫（高pH）对种子萌发的影响可能是极其复杂的,在低pH值时,小麦种子的萌发没有被抑制,但是在高盐度时产生抑制。低强度碱胁迫下,萌发的种子似乎可以通过代谢活动降低外界pH。在高碱浓度下,高pH可能造成种子内部结构被分解和破坏,甚至导致种子死亡。这可能是一个复杂的反应过程,值得我们深入研究。盐碱胁迫下小麦、羊草、赖草、和狗尾草四种禾本科植物的生长速率和水分利用效率都随着盐度的上升而降低。其中,碱胁迫的下降幅度要远远大于盐胁迫,即在相同的处理液浓度下,碱胁迫对植物的伤害要大于盐胁迫。碱胁迫对植物的伤害甚于盐胁迫的原因可能与两种胁迫的作用机制有关,盐胁迫主要是渗透胁迫及离子毒害,而碱胁迫除包括这两种胁迫作用外,还包括高pH胁迫。土壤中的高pH可以直接造成Ca²⁺和Mg²⁺离子的沉淀,破坏植物对营养物质的吸收,进而造成根周围的营养失衡。盐碱胁迫除了明显地抑制生长外,也明显地影响植物光合碳同化。四种植物的光合能力在低、中浓度的盐胁迫和低浓度的碱胁迫下变化不大;随着盐浓度的增加光合参数急剧下降,碱胁迫下光合参数下降趋势更加明显。这些结果表明碱胁迫的高pH能够强烈地抑制植物光合作用。碱胁迫可能通过破坏光合器官和影响气孔导度来限制光合作用,这可能与细胞中积累过多的Na⁺,而产生毒害有关。叶绿素荧光实验也可以证明这一点,高pH胁迫造成大量的Na⁺进入植物细胞内,进而造成光抑制,阻碍光能的吸收并引起PSⅡ最大光化学效率反应器活性下降,而且盐碱胁迫严重地阻碍受损伤的PSⅡ反应中心的自我修复。根茎叶中Na⁺含量均随着胁迫强度的增加而增加,而K+含量则呈明显的下降趋势。在碱胁迫下,Na⁺和K⁺含量的变化要明显地大于盐胁迫,即碱胁迫促进了根系对Na⁺的吸收和转运,而抑制K⁺离子吸收和转运,最终导致植物体内离子失衡和pH不稳定。Ca²⁺、Mg²⁺和Fe²⁺对两种胁迫的反应与以往报道有所不同,均随胁迫强度的增加而增加,这可能是植物对碱胁迫的一种胁变反应,可能是特定的适应性反应,值得深入研究。虽然Ca²⁺、Mg²⁺和Fe²⁺含量在碱胁迫下增加,但是它们对渗透调节的影响不大,主要是因为它们在离子含量中占的比例很低。研究材料小麦、羊草、赖草和狗尾草这四种禾本科植物在盐胁迫下均大量积累有机酸,均以苹果酸和柠檬酸为主要成分;均通过积累有机酸来平衡大量的Na⁺,来弥补无机阴离子的缺失,维护细胞内离子平衡和pH稳定。综合分析表明,有机酸在茎叶中的积累不是一个简单的被动响应,而是在碱胁迫下的一个积极的代谢调控结果。由此提出:在碱胁迫下有机酸的代谢调控可能涉及到一个或多个已知的基础代谢途径。如果有机酸的响应可以被清楚地解释,植物抗盐碱的关键基因就会很容易识别和克隆出来。关于有机酸的研究可能是未来盐碱胁迫研究的一个主要的方向或分支。更多还原

【Abstract】 Arable land has been tightly coupled with the socio-economic development and the rapid growth of the world’s population, but it has been severely affected by soil salinity. The arable land is affected by salt throughout the world; plants growth and productivity are severely affected by soil salinity. The detrimental effects of high salinity on plants can be observed at the whole-plant level as the death of plants and/or decrease in productivity. The effects of saline and alkaline stress on plants were multiple pathways, so the ability of plants to tolerate stress is determined by multiple biochemical pathways. Different plant species may have completely different stresses adaptation mechanisms, it is necessary to summarize and compare the responses and adaptive adjustment mechanisms of saline-alkaline stress in different plant species. Gramineae plants are the type which have been more concentrated studied, it includes many saline stress tolerate types. In order to summarize and compare the adaptive adjustment mechanisms of saline-alkaline stress in gramineae plants, we chose four different gramineae plants they were Triticum aestivum Linn, Leymus chinensis, Leymus secalinus and Setaria viridis. Based on the saline soils of grasslands in northeast China, the natural salinity stress in natural saline soils is very complex. Two neutral salts were mixed at a 1:1 molar ratio of NaCl: Na2SO4 and applied to the saline stress group. Similarly, two alkaline salts were mixed at a 1:1 molar ratio of NaHCO3 to Na2CO3 and applied to the alkaline stress group. There were five concentrations for the saline and alkaline stresses: 30, 60, 90, 120 and 150 mM. To further explore the saline-alkaline stress adaptation mechanisms of gramineae plants（four species）by measuring the germination rate, relative growth rate, water content, photosynthesis parameters, ionic balance and organic acids.Germination is one of the most critical periods in the life cycle of plants, but it can be affected by abiotic stresses. Under saline-alkaline stress, low water potential is a decisive factor to inhibit the seed germination. The results indicated that alkaline stress more significantly affected seed germination than saline stress. Non-germinated seeds in dormancy to avoid adverse environment. Perhaps alkaline stress （high pH value） on seed germination could be extremely complex, and the low pH value didn’t inhibit the germination of wheat seeds, on the contrary to the high salinity. Under low-intensity alkaline stress, the germinated seeds can decline pH value by metabolic activities. The high pH stress may decompose the seed structure, eventually leading to seed death, may be it is a complex reaction process, and be worth studying in-depth. Under saline-alkaline stress, the relative growth rate and water use efficiency of four gramineae plants decreased with increasing salinity, and the decrease for alkaline stress is much greater than for saline stress at the same concentration. Salt stress is mainly osmotic stress and ion toxicity, the harmful of alkaline-stress on plants is greater than saline-stress, the main reason may be alkaline-stress includes high-pH stress. The high pH in soil can be direct cause Ca2+ and Mg2+ precipitated, destroy plant absorb nutrients and then cause nutritional imbalances around the root in the plants.Except saline and alkaline stress obviously inhibited the growth of plants, we also discovered that the saline-alkaline stress is significantly affects on photosynthetic carbon assimilation in plant. Photosynthetic capacity of four plants had changed little under low and moderate concentrations of saline stress or low concentrations of alkaline stress; but photosynthetic parameters declined rapidly with increasing salinity, the extent of reduction under alkaline stress was significantly greater than under saline stress. These results appeared to confirm that the high pH value of alkali-stress can be a strong inhibition of plant photosynthesis. Alkaline stress can restrict photosynthesis processes by damaging the photosynthetic apparatus and stomatal conductance in plants; this may be related to excessive accumulation of Na⁺ in cells, and then causing poison. The Chlorophyll fluorescence experiments can also prove this point, high-pH stress caused a large number of Na⁺ influx into plant cells, causing photoinhibition and impede the absorption of light energy and cause the activity of the maximal photochemical efficiency of PSⅡreactor decreased. And the saline-alkaline stress severely hampered self-repair of the injury of PSⅡreaction center.The results indicated that the contents of Na⁺ in plants increased with increasing stress intensity, and the contents of K+ decreased rapidly. The Na⁺ increase and K+ decrease under alkaline stress were greater than under salt stress with increasing stress intensity. This showed that the high pH value of alkaline stress may interfere with the absorption of Na⁺ in roots, make the accumulation of intracellular Na⁺ to the poison level. Under alkaline stress, the increasing Na⁺ may not be the response to osmotic stress, but the response to high pH value. The absorption and transportation of Na⁺ in roots are promoted under alkaline stress, but inhibit K⁺, and eventually result in ion imbalance and unstable pH in plants. The response to two stresses of Ca²⁺, Mg²⁺ and Fe²⁺ was different from the previous reports, they increased with increasing stress intensity in this experiment, and this may be plants response to alkaline stress in order to avoid stress threat. It may be a specific adaptive response, so it is worth studying in-depth. Although the contents of Ca²⁺, Mg²⁺ and Fe²⁺ increased under alkaline stress, they have little effect on the osmotic adjustment; mainly because of they have a low proportion of the ion contents.The four gramineae plants didn’t accumulated organic acids under saline stress, but accumulated substantial organic acids under alkaline stress, malic acids and citric acids are the main components. In order to balance substantial Na⁺, compensate the deficit of inorganic anions, and maintain intracellular stable pH, plant enhanced the synthesis of the organic acids （OA） anions, indicating that OA metabolic regulation played a central role in intracellular pH adjustment of plant. The accumulation of organic acids in the stems and leaves not a simple passive response to salt stress, it is a positive result of metabolic regulation under alkaline stress. The metabolic regulation of OA under alkaline stress may involve in one or more basal metabolic pathways. It is easy to identify and clone the key gene of anti-saline and anti-alkaline in plants, if the response of organic acids could be clearly explained. Thus, the research on organic acids may be the main direction or branch of salt-alkaline stress in the future.更多还原