【作者】 王芳；

【导师】 岳明；

【作者基本信息】 西北大学 ， 生态学， 2009， 硕士

【摘要】 臭氧层减薄而导致的UV-B辐射日益增强,同时温室效应而导致的全球变暖加剧了干旱对于植物的胁迫效应。植物在长期进化中形成一套完整的生理生化机制适应所处的生态环境,从而赋予植物不同的环境耐受性。而在日益复杂的环境背景下,单一性的研究一种胁迫因子是不够的。本研究采用了增强的UV-B和干旱两种胁迫因子作为环境因子进行室内实验,考察了非抗旱品种CS和抗旱品种R7在两胁迫因子单独胁迫和复合胁迫下生理生化水平的各种响应,试图探究不同抗旱性的玉米品种对于UV-B辐射的敏感性和UV-B辐射和干旱胁迫之间的交互效应,由此理解并推测植物在响应环境变化的交互网络。对研究结果进行整合分析后,得出以下结论:1.不同抗旱性的玉米品种对UV-B的敏感性不同。在干旱下抗旱品种R7维持了正常平稳的MDA含量,膜透性变化不大,可溶性蛋白含量较低,水分敏感品种CS则相反。结果符合品种的抗旱性:非抗旱性CS在水分亏缺的条件下更易受到伤害。UV-B辐射并未造成与干旱相等程度的伤害,但选用的抗旱品种R7叶片维持更高的SOD活性,24h胁迫处理后,CAT、APX活性显著升高,根部在胁迫后期快速积累脯氨酸,并在根部维持高的SOD活性。抗旱品种R7通过维持高活性的SOD、CAT和APX抗氧化酶活性并累积大量游离的Pro抵御逆境,对UV-B辐射表现出一定的耐受。抗性不同的植株对于不同的胁迫环境表现不同的耐受性,这是植物适应环境的表现;2.UV-B辐射和干旱胁迫的复合胁迫之间有交互作用,但表现为拮抗作用还是协同作用是随着指标的性质不同而变化的。抗氧化酶体系中,24h复合胁迫使CS叶片中的SOD活性高出单独胁迫,根系中的SOD活性降低了近7倍;对于抗旱的R7,叶片中的CAT和APX及根系中的CAT活性复合胁迫都表现为拮抗作用。另外,非抗旱品种CS24h的UV-B辐射并未显著增加类黄酮的含量,在干旱下却增加了1.4倍,复合胁迫情况一致,而在抗旱品种R7体内的类黄酮含量与CK比较显著增加,两胁迫单独作用时虽然有所累积却不明显。由此推测,玉米在复合胁迫下受到的氧化伤害较小,即增强的UV-B辐射可以缓解干旱的造成的氧化胁迫。这种正面效益在CS和R7两品种的体现不同。复合胁迫之间的协同作用在水分敏感的品种中被掩盖,而在抗旱品种中则体现出来,也就是说当植物对水分条件敏感时,UV-B辐射的胁迫效应往往被水分亏缺所造成的伤害掩盖。植物对于水分条件的变化更为敏感,而光辐射伤害则通过不同的路径刺激植物减缓水分胁迫造成的压力;3.根系和根上部对于不同胁迫响应不同。玉米在胁迫下仍保持体内水分,根系会保持比地上部分更高的水势,并且合成大量的脱落酸调节地上部分的响应事件。而叶片则提升SOD、CAT和APX活性保持更积极的抗氧化体系来调节植株整体的生理生化时间,以此来适应胁迫环境。这是植物器官之间分工不同协调合作的表现。4.12h的干旱胁迫下根系直接感受胁迫信号,促使ABA的合成并快速转运至叶片,激活叶片中的抗氧化系统。UV-B辐射下ABA在24h胁迫后积累量才变得明显,而各种细胞组分变化未达到干旱胁迫下的程度,并且都表现的比较滞后,因此推断ABA不是UV-B辐射诱导的初级信号分子,而UV-B胁迫造成的伤害是一种累积效应,在短期的24h胁迫中表现不明显,因此UV-B所造成的氧化伤害或缓解干旱的效应应是通过其他的路径造成的。为对UV-B诱导的直接信号分子作出解释,建议进行长期的UV-B实验,并考虑其他的信号分子,如NO、乙烯等。更多还原

【Abstract】 The depletion of 03 has been resulting UV-B enhancement and meanwhile the global warming induced by greenhouse effect deteriorates drought-stressed environment. Plants have developed a full set of physiological and molecular mechanisms that confer the plants to adapt the complicated eco-environment which include the extreme environments risking the growth, development and propagation of botany. The research on single stress environmental factor is no longer enough with the more complicated climate changing background. This research considered the enhanced UV-B and drought as stress factors for greenhouse experiment design and examined different physiological indexes of two maize cultivars, drought-sensitive CS and drought-resistant R7. The final research aim was to explore how the two cultivars with different water-sensitive traits would respond to enhanced UV-B radiation and the interactive effects between UV-B and drought, both being speculating the crosstalk between the pathways in which plants respond to different environmental conditions.Through the results, the conclusions are listed as follows:1. Different sensitivity to drought was consistent with that to enhanced UV-B. Drought-resistant cultivar R7 maitained a steady MDA content and membrane permeability and low soluble protein content. CS was in an opposite position. The result verified the cultivar trait: drought-sensivie cultivar was more injured in drought condition. Though UV-B radiation did not imposed the damage as drought, a high SOD, CAT and APX acitivity was maintained in R7 leaves. Meanwhile, Pro was accumulated rapidly in root. These regulations of the anti-drought cultivar in UV-B presented the tolerance of plants to different environment;2. The positive interaction was observed between UV-B and drought but changed with different indexes. In antioxidant system, 24h combined stress pushed up the SOD activity in CS leaves and suppressed 7 times down in root system and presented an antagonium in CAT and APX in leaves and CAT in root of R7. Otherwise, flavonoids increased 1.4 times in sensitive CS cultivar in drought condition and conbined stress. It obviousely accumulated in combined stress but not in each single stress. To sum up, UV-B run a relief in the oxidation. The bright side changed with cultivars. The positive effects were covered in drought-sensitive cultivar while emerged in anti-drought cultivar, which meant plants were more sentive to the water condition and UV-B radiation must be avoiding the drought-induced signal pathway to relieve the drought stress;3. The responses to stress from root and shoot were different. Totally maizes held a higher RWC (water potential as well) and synthesized and transported abundant ABA to regulate the antidative cases in shoot. It manifested the labor division of root and shoot;4. In drought, root system directly sensed the environmental signals and spured ABA accumulation. In 12h drought, ABA was transporting from root to shoot to activate the antioxidative system. Only after 24h UV radiation ABA was obviously accumulated but not in drought-condition amount while the responses of all the indexes were not active as in drought and retarded always. It was deduced that ABA was not the first-hand signal which UV-B excited in the whole stress-induced signal network. Also the relief effects of oxidative hurt UV-B made should practiced through other pathways. A long-term UV-B experiment considering other signals like NO and ethylene is suggested to investigate the the first-hand UV-induced signal.更多还原