水分胁迫下小麦幼苗呼吸代谢的改变

水分胁迫下小麦幼苗叶和根的呼吸速率变化模式不同:叶片呼吸在胁迫初期升高,然后随相对含水量进一步递减而急剧下降;根的呼吸速率随相对含水量降低成指数下降。自然干旱和PEG渗透胁迫下得到的结果基本一致。小麦叶片在轻度水分胁迫下呼吸上升与磷酸化解偶联有关。水分胁迫也引起呼吸代谢途径的改变。轻度水分胁迫使叶片呼吸速率升高时,EMP途径运行程度稍有上升;增加的呼吸主要通过TCAC;线粒体呼吸中通过细胞色素主链的电子流量增加,抗氰交替途径的相对运行程度下降。当水分胁迫降低根呼吸速率时,EMP和TCAC的运行程度明显降低;细胞色素途径的运行程度也下降,但仍传递大约一半的呼吸电子流。

CHANGES IN RESPIRATORY METABOLISM OF WATERSTRESSED WHEAT SEEDLINGS

From the experimental results it was seen that water stress caused a series of changes in respiration of wheat seedlings. Respiratory rate in young leaves rose from the beginning of stress. When relative water content (RWC) of the leaf was further reduced, respiratory rate declined speedily. Respiratory rate of wheat roots declined exponentially under stress. The changes in respiratory rate of wheats under natural drought and under osmotic stress induced by PEG solution were essentially the same. Respiratory increase in wheat leaves is related to phosphorylating uncoupling under slight water stress.The experimental results with respiratory inhibitors showed that EMP and TCAC operated in leaves and roots Of wheat. The increase of respiration in leaves under slight osmotic stress was mainly mediated by EMP and TCAC. There was cyanide-resistant alternate pathway in the mitochondria respiration of wheat leaves, but the bulk of respiratory electron flux was still mediated by the cytochrome pathway. The relative role of the alternate pathway in respiration slightly decreased under osmotic stress. EMP and TCAC accounted for most part of the metabolism of respiratory substrates in roots. When the respiration of roots declined under osmotic stress, the contribution of EMP and TCAC decreased and most of the respiratory electron flux were still mediated by the cytochrome pathway, though the percentage relative of respiration inhibitedby KCN declined. The relative importance of the alternate pathway was low in roots, and it increasod slightly under osmotic stress.