水分胁迫对小麦根细胞质膜氧化还原系统的影响

水分胁迫使小麦根质膜ＮＡＤＨ和ＮＡＤＰＨ的氧化速率及Ｆｅ（ＣＮ）６３－和ＥＤＴＡ－Ｆｅ３＋的还原速率明显降低。对照与胁迫处理的质膜氧化还原系统活性均不受鱼藤酮抗霉素Ａ和ＫＣＮ等呼吸链抑制剂的影响。在不加Ｆｅ（ＣＮ）６３－作为电子受体时，水杨基羟肘酸（ＳＨＷ）可明显刺激质膜ＮＡＤＨ的氧化和Ｏ２吸收速率。水分胁迫促使ＳＨＡＭ刺激的ＮＡＤＨ氧化明显降低，但却使Ｏ２吸收略有上升。

Effect of Water Stress on the Redox System of the Plasma Membrane of Wheat Roots

Plasma membranes were isolatedand purified from the roots of 6--dayold wheat seedlings by aqueous twophase partitioning. Wheat seedlingswere water--stressed by placing in 20%PEG--6000 for 10 h. The resultsshowed that water stress caused a remarkable change in the structure, constitution and function of plasma membrane ; protein content decreased, H ATPase activity was stimulated and thetriton effect disappeared. The oxidation of NADH and HADPH and the reduction of Fe(CN), and EDTA--Fe3 decreased to 75%, 78%, 84% and78% respectively, of the control afterwater stress. The inhibitors of mitochondrial respiratory chains, retenone,antimycin A and KCN, did not haveany effect on the redox sysetm of plasma membrane. SHAM had a stimulatory effect on NADH oxidation and O2uptake, which could be inhibited byKCN. It was suggested that there weretwo distinct NADH oxidases in plasmamembrane of wheat roots. Water stresscaused a great decrease (61 % ) inSHAM--stimulated NADH oxidation.However, SHAM-stimulated O2 uptakeincreased by 25% of the control. Kinetic analysis showed that the Km ofNADH oxidation increased, but that ofO2 uptake decreased. The differencesin NADH oxidation and O2 uptake indicated that O2 was not the electron acceptor of NADH oxidation stimulated.by SHAM. It could also be indicatedthat an unknown redox system wasstuned and some unknown compoundscould replace NADH as electron donorsafter water stress.