氮素营养水平对棉花衰老的影响及其生理机制

 【目的】探讨在大田条件下，土壤氮素含量水平对棉花生长过程中叶片生理生化指标、干物质积累量、组织含水量、叶面积载荷量的影响，为调控棉花早衰和提高棉花产量提供依据。【方法】设置3个氮素水平（纯N：低氮 0 kg?hm-2;中氮189.50 kg?hm-2;高氮395.0 kg?hm-2）处理，研究棉花衰老过程中主茎功能叶的生理生化指标变化，植株的干物质积累量、组织含水量及载荷量特征。【结果】盛铃末期为处理间生理生化指标产生差异的起始时期。与中氮、高氮相比，从盛铃末期开始，低氮处理棉花的叶绿素含量、蛋白质含量、SOD和POD活性降低，组织含水量和干物质积累量快速下降，而MDA含量、叶面积载荷量快速升高，加速了棉株衰老的进程。增加氮素营养能够明显提高叶片的生理活性，提高组织含水量和干物质积累量，延缓衰老。【结论】在本试验条件下，盛铃末期是棉花叶片生理功能从旺盛生理功能到衰退的转折时期。土壤氮素含量与棉花衰老密切相关，低氮处理加速降低叶片的生理活性，造成早衰;中氮和高氮水平能够延缓棉花衰老现象。

Effects of Nitrogen on Cotton Senescence and the Corresponding Physiological Mechanisms

【Objective】 The effects of N content in soil on the physiological and biochemical indexes, amount of dry-matter accumula, tissue water content, boll load per unit leaf in cotton were studied in the field. 【Method】 The physiological characters of the leaves on stem , amount of dry-matter accumulation and tissue water content of the above-ground cotton plants, boll load per unit leaf was studied under different N levels (low level, 0 kg?hm-2, middle level, 189.50 kg?hm-2, high level, 395.0 kg?hm-2). 【Result】 The turning point from bloom to senescence is at the later full boll stage. The results showed that there was a negative correlation between nitrogen and the cotton premature senescence. Compared to mid-nitrogen and high-nitrogen treatments, under the condition of low nitrogen, the content of Chl. and dissolvable protein, photosynthetic rate, the amount of dry-matter accumulation and the activities of SOD and POD all decreased. But the content of MDA and boll load per unit leaf increased. It was concluded that cotton had a faster senescence under low nitrogen treatment. However, the efficiency of nitrogen decreased with the increase of nitrogen (from middle N level to high N level). 【Conclusion】N content in soil affects the cotton senescence remarkably. Low-nitrogen decreased the physiological characteristics of leaves, and protmoted the senescence; mid-nitrogen and high-nitrogen delay aging.