【作者】 彭海欢；

【导师】 翁晓燕；

【作者基本信息】 浙江大学 ， 植物学， 2006， 硕士

【摘要】 本研究测定水稻在自然衰老及缺钾胁迫下气体交换、叶绿素荧光参数的变化，并且结合抗氧化酶指标的测定结果系统分析了自然衰老及缺钾条件下早衰的原因。 水稻剑叶在抽穗后，净光合速率Pn及Fv／Fm、Φ_PSⅡ、qP、ETR等叶绿素荧光参数均开始下降。随着衰老的进行，水稻的NPQ和SOD活性亦表现出了下降趋势。水稻在自然衰老的过程中，光合能力下降，光合机构受到不可逆转的破坏。同时，热耗散机制和活性氧清除系统亦受到了损伤，从而使体内过剩光能无法耗散掉，膜脂过氧化加剧，最终导致植物一步步走向衰老和死亡。 在缺钾条件下，水稻的Pn、Gs随着处理时间的延长而下降；同时光合色素、可溶性蛋白含量降低。进一步的叶绿素荧光特性研究表明，随着钾胁迫时间的延长，缺钾水稻叶片中的F_v／F_m、Φ_PSⅡ、qP及ETR均显著下降，说明PSⅡ反应中心受到伤害。缺钾也降低了水稻叶片的光饱和点，PSⅡ吸收的光能超过了光合作用所能利用的光能。缺钾叶片NPQ显著上升，说明钾胁迫下的水稻叶片通过启动热耗散机制耗散过剩的激发能，以减轻因PSⅡ吸收过多光能而引起的光抑制和光氧化从而保护光合机构免受伤害。在整个处理过程中，缺钾植株的抗氧化酶活性先上升后下降，这说明在缺钾初期，水稻叶片抗氧化酶活性增强以清除体内的活性氧。与二九丰相比，原丰早具有更强的清除活性氧的能力，使其在缺钾条件下具有更强的自我保护能力，因而对缺钾表现出更强的耐性。更多还原

【Abstract】 Physiological, photosynthetic characteristics and antioxidant enzymes activities were studied in leaves of rice plant during natural senescence and under Potassium Deficiency. Meanwhile, the cause of natural senescence and premature senility under potassium deficiency were also discussed.After rice heading, Pn, Fv/Fm, Φps(?), and qP were decreased in flag leaves, and so was photosynthetic pigments, soluble protein. As the time extending, NPQ and SOD activity were also declined. During natural senescence, photosynthetic ability was reduced in leaves, and its photosynthetic system was damaged irreversibely. In the end, thermal dissipation mechanism was suppressed, the excessive excitation energy couldn’t be dissipated efficiently which accelerated the damage to the photosynthetic system. Furthermore, the activity of antioxidant enzyme (SOD) was decreased and accelerated the membrance liquid peroxidation, and led the plant to senescence.The net photosynthetic rate (P_n) and stomatal conductance (G_s) decreased significantly, in the potassium deficient leaves. At the same time, the photosynthetic pigments and soluble protein declined. The further study on chlorophyll fluorescence measurement showed that F_v/F_m, Φps(?), qP and ETR were declined as time extended under potassium deficiency, indicating that the PS II reaction center was damaged. Potassium deficiency also decreased the light- saturation points in both cultivars. In that conditions, the light energy absorbed by PS II was in excess of the need for assimilation. We also detected a significant increase of NPQ in the stressed leaves of both cultivars, which indicated that the mechanism of thermal dissipation had been started to dissipate excess light energy, and protect the plants from photo-inhibition and photo-oxidation. During the whole potassium deficiency period, the activities of antioxidant enzymes were first increased and then decreased. Antioxidant enzymes were involved in scavenging active oxygen species. In our results, YFZ’s antioxidant更多还原