干旱胁迫下氮肥对玉米叶片衰老影响及与碳氮平衡的关系
为探究干旱胁迫下氮肥对玉米叶片衰老和叶片碳氮平衡的影响,以及碳氮平衡和叶片衰老及抗旱性的关系。以玉米品种兴民18为研究材料,设置高氮和低氮两个氮水平,通过盆栽人工控水的方式,进行干旱和复水处理。在干旱胁迫下,高氮处理下玉米叶片光合速率、叶绿素含量等衰老指标显著低于低氮,即高氮增加了玉米对干旱的敏感性和加快了干旱胁迫下玉米叶片的衰老进程；干旱胁迫诱导玉米叶片衰老的同时,碳氮比显著升高,说明碳氮平衡可能参与了干旱诱导的叶片衰老调控。另外,在干旱胁迫及复水条件下,高氮处理下玉米下部衰老叶片中的氮浓度并不比低氮高,而干旱条件下高氮的碳氮比相较于低氮增加幅度更大,碳氮平衡受干旱破坏程度更严重,说明高氮并不能增加干旱胁迫后下部衰老叶片中的氮浓度,也不能缓解干旱胁迫引起的碳氮失衡。干旱胁迫下高氮导致碳氮失衡加剧,而碳氮失衡加剧可能是高氮增加了玉米对干旱的敏感性和叶片加速衰老的原因之一。
英文摘要:
To investigate the influence of nitrogenous fertilizer on carbon/nitrogen balance of senescent leaves under drought stress, and the association of the nitrogenous fertilizer and the drought-induced leaf senescence with drought resistance. The maize cultivar Xingmin 18 was potted and treated with two nitrogen levels (high nitrogen and low nitrogen respectively), as well as drought stress and rehydration. Our results indicated that the symptoms of leaf senescence such as photosynthesis and chlorophyll content under high nitrogen condition were lower in comparison with low nitrogen condition. The nitrogen increased the drought sensitivity of maize and did not alleviate the leaf senescence under drought stress. Drought stress induced the maize leaf senescence accompanied with the increase of Carbon/Nitrogen ratio. Therefore, carbon and nitrogen metabolisms were tightly associated with drought-induced leaf senescence, and the carbon/nitrogen balance may involve in the regulation of drought-induced leaf senescence. Furthermore, the nitrogen concentration in maize leaf on high nitrogen level was not higher than that on low nitrogen level, and compared with low nitrogen level, the C/N imbalance of high nitrogen levels was more serious under drought stress, which indicated that the nitrogen concentration in maize leaf was not increasing under drought stress when increased nitrogenous fertilizer, and also couldn’t alleviate carbon/nitrogen imbalance that caused by drought stress. The results showed that, under drought stress, carbon/nitrogen imbalance was more serious under high nitrogen condition. And it may be one of the reasons for that high nitrogen level increased the sensitivity to drought stress and accelerated leaf senescence.
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