低温吸胀对PEG引发大豆种子呼吸和氧化磷酸化的影响

EFFECT OF LOW TEMPERATURE IMBIBITION ON MITOCHONDRIUM RESPIRATION AND PHOSPHORYLATION OF PEG PRIMED SOYBEAN SEED

本文研究了低温吸张对聚乙二醇(PEG)引发大豆(Glycine max)种子在萌发过程中子叶线粒体的呼吸和氧化磷酸化活性的影响。当以 L-苹果酸(L-Mal)、α-酮戊二酸(α-Kg)和琥珀酸(Succ)为底物时,加入 ADP 后,发生吸胀冷害种子(对照)线粒体呼吸速率比引发种子线粒体状态Ⅲ呼吸速率还高。对照的线粒体呼吸控制解除,ATP 合成受到抑制;而PEG 引发种子线粒体氧化磷酸化功能正常,ADP/O 和 RC 值均与理论值相符。当以 NADH为底物时,对照种子在低温处理后仍有氧化磷酸化活性,但 ADP/O 和 RC 降低25—30%,引发种子子叶线粒体氧化不同底物出现磷酸化活性的顺序是:NADH(12小时),α-Kg(24小时),L-Mal 和 Succ(48小时)。对照种子线粒体利用不同底物时,ADP 呼吸促进效应出现的顺序与之相同。讨论了大豆种子发生吸胀冷害的原因和 PEG 引发的防护机理。

Cotyledon mitochondrium respiration and oxidative phosphorylation activity of PEG pri- med and unprimed(control)soybean seeds which have been exposed to low temperature imbi- bition before germination are studied.The ADP stimulated respiration rates of control mito- chondria are evidently higher than state Ⅲ respiration rates of mitochondria from primed seed when L-Mal,α-Kg and Succ are used as substrates respectively.The mitochondria from the unprimed do not possess respiratory control(RC.)On the contrary,mitochondria from the primed,even after seeds being exposed to 2—3℃ imbibition for 24 h,phosphorylate normally. The ADP/O and RC values are consistent with those of theoretical expectation.When NADH is used as substrate,unprimed seed mitochondria still possess oxidative phosphorylation activi- ty,while ADP/O and RC values are obviously lower than those of mitochondria from the pri- med.The emerging sequence of the activity of the diverse phosphorylation sites during germi- nation is also studied.When a different substrate is used,the emerging sequence of the primed is as follows:1.NADH(12h),2.α-Kg(24h),3.L-Mal and Succ(48h).This corresponds to occurrence sequence of ADP stimulated respiration in control mitochondria.The above results show that low temperature imbibition has an irreversible destructive effect on oxidative phos- phorylation activity of control mitochondria,and PEG priming has a protective effect on struc- ture and function of the mitochondria under low temperature imbibition stress.The mechanism of soybean imbibitional chilling injury and protective effect of PEG priming are discussed.