【作者】 刘芳；

【导师】 许晓明；

【作者基本信息】 南京农业大学 ， 细胞生物学， 2008， 硕士

【摘要】 光合作用是植物生长发育的基础,它为植物的生长发育提供需要的物质和能量,而低温强光又严重影响水稻的生长发育,因此,研究如何缓解低温强光下水稻的光抑制具有的重要的意义。5-氨基乙酰丙酸（ALA）是所有生物卟啉类化合物如叶绿素、亚铁血红素等的一个关键前体物。在植物中,高浓度的ALA能用作除草剂,而低浓度的ALA则能调节植物生长发育,促进作物增产,以及提高植株的耐盐性及冷适应能力。本研究以水稻为材料,通过测定外源ALA对低温强光下水稻叶绿素a荧光诱导动力学特性的影响,分析了ALA对水稻叶片光系统Ⅱ的原初光化学反应过程以及光系统Ⅱ稳定性的调节作用。结果表明外源ALA能够减轻水稻叶片的低温强光胁迫,其中一个重要原因是它提高了低温强光下水稻叶片PSⅡ的稳定性,ALA通过减轻PSⅡ受体侧的伤害,保持较高的电子传递活性,从而使QA在低温下仍能保持较为氧化的状态,减少了失活的反应中心。本研究还明确了喷施ALA的水稻叶片能明显缓解PSⅡ的光抑制的另一重要原因,发现喷施低浓度ALA的水稻叶片能缓解低温光抑制的主要途径不是通过增强依赖于叶黄素循环的热耗散,而是通过显著增加叶绿体抗氧化酶系统中GR和APX的活性,稳定SOD活性,清除积累的H₂O₂,从而缓解PSⅡ的光抑制。而APX的活性增加主要是由亚铁血红素库积累造成的。更多还原

【Abstract】 Photosynthesis is the basis of growth and development of plant,it provides the substrates and energy for growth and development.Low temperature as well as high light intensity stress effects photosynthesis.Therefore,it is important to study the mechanisms that how the stress effects photosynthesis.ALA is a key precursor in the biosynthesis of porphyrins such as chlorophyll and heme,Its high concentration is used as a herbicide,and in low concentration,it can judge growth,increase production of crop,and heighten resistance to salt and cold adaptability.We studied the influences of exogenous 5-aminolevulinic Acid（ALA） on photochemical efficiency, thermal dissipation、photochemical reaction and other physiology process of photosystemⅡand analyzed its regulation on photosystemⅡunder low temperature as well as high light intensity in rice.Our results suggested that the excess energy was mainly reduced by thermal dissipation.However,ALA could adjust the allocation of absorbed energy and increase energy flowing to photochemical so as to reduce excess energy in leaves.Moreover,ALA also could alleviate harm to the acceptor of PSⅡ, maintain the higher electron-transferring activity,keep QA to do oxygenation under low temperature as well as high light intensity and reduce inactivation of PSⅡreaction centre so as to enhance the stability of PSⅡunder low temperature as well as high light intensityThe another mechanism of significant increase in resistance to low temperature photoinhibition was studied.Low concentration ALA-treatment enhanced the resistance of rice,because of the significant enhancement of the ascorbate peroxidase （APX） and glutathione reductase（GR） activities as well as the less reduce in superoxide dismutase（SOD） activities which alleviate photoinhibition of photosystem 2 by reducing accumulation of the hydrogen peroxide（H₂O₂） in chloroplast instead of the enhancing of thermal energy dissipation by xanthophylls cycle.Moreover,the increased activity of the ascorbate peroxidase（APX） was probably resulted from the accumulation of heme content.更多还原