氮素营养调控小麦旗叶衰老和光合功能衰退的生理机制

研究表明，氮素营养提高了旗叶老化过程中的叶绿素含量和光合速率，延缓了叶片衰老和光合功能衰退，增加了旗叶内细胞分裂素类物质（ZRs）含量，减少了促表激素ABA的累积量。氮素处理使旗叶老化过程中光合机构的RuBPcase活性和PS1、PS2活性均得以增加，但氮素对RuBPcase活性下降的延缓效果更为明显，相对增加了叶片老化过程中RuBPcase活性与PS1和PS2活性的比值，使光合机构光反应与暗反应之间的平衡状况得到改善，过剩还原力减少。此外，氮素营养使旗叶老化过程中超氧阴离子（O2-）的产生速率降低，H2O2的累积量减少，并提高细胞中活性氧清除酶SOD和CAT的活性。氮素营养可能主要通过调节细胞内的激素平衡，以及改善光合机构的自身运转平衡状况，减少了细胞中对生物体具有强烈伤害的活性氧的产生速率及其累积数量、提高了活性氧清除酶的活力，由此在很大程度上延缓了旗叶的衰老和光合功能衰退，延长了旗叶的光合功能期。

THE PhYSIOLGICAL MECHANISM OF SENESCENCE AND PHOTOSYNTHETIC FUNCTION DECLINE OF FLAG LEAF IN WHEAT REGULATED BY NITROGEN NUTRITION

The results indicated that nitrogen nutrition supplied at flag leaf initiation could increase the chlorophyll content and photosynthetic rate, delay the senescence and photosynthetic decline of leaf during leaf aging process. At the meantime, nitrogen nutrition made the leaf cytokinin(ZRs) content increase and abscisic acid(ABA) content decrease. Duing leaf aging process, nitrogen treatment could also increase the RuBPcase activity, PS1 and PS2 activity, but the increase of RuBPcase activity was much higher than that of PS1 and PS2 activity. Which relatively increased the rations of RaBPcase activity to PS1 activity and PS2 activity, and improved the balance state between the light reaction and dark reaction of photosynthetic organ. The suplus photosynthetic reductivity produced by light reaction was little. Otherwise, compared with CK, nitrogen nutrition decreased the O₂ Producing rate and the accumulation amount of H₂O₂ in leaf, and increased the enzymatic activity of active scavenging enzyme SOD and CAT during leaf aging process. It is suggested that nitrogen nutrition probably is mainly by regulating the hormone balance in the leaf cell, and improving the cycling metabolism of the photosynthetic organ. to decline the producing rate and accumulation amount of active oxygen in the leaf, and inhance the activity of active oxygen scavenging enzyems. Which is one important physiological factor that the leaf senescence and the photosynthetic function decline can be delayed regulated by nitrogen nutrition.