镉(Cd)与UV-B复合胁迫影响大豆胚轴生长的生理调节机制研究

通过研究大豆胚轴生长及内源吲哚乙酸(IAA)、赤霉素(GAs)、过氧化物酶(POD)和吲哚乙酸氧化酶(IAA oxidase)活性变化对Cd、UV-B辐射和Cd UV-B(复合胁迫)的响应。分析了激素水平、酶活性变化以及胚轴生长变化特性。结果表明，UV—B辐射引起大豆上胚轴伸长减小；但Cd对上胚轴伸长无明显影响；Cd UV—B使上胚轴长度比UV—B作用时明显增加。UVB辐射显著降低了胚轴IAA含量；而GAs含量却显著升高；Cd胁迫下IAA和GAs变化并不明显；但Cd UV—B使IAA含量显著升高，而对GAs无明显影响。UVB辐射使IAA氧化酶和POD活性显著增强，而Cd对这两种酶活性影响并不明显；但Cd UV—B复合胁迫下胚轴的IAA水平较高。尽管UVB辐射引起胚轴中GAs含量显著增加，但研究结果显示IAA含量变化是胁迫下引起胚轴生长改变的更直接原因。研究还表明Cd UV—B时，大大削弱了UV—B辐射下IAA氧化酶活性增强，加之Cd对POD活性的抑制，导致复合胁迫下胚轴的IAA水平较高。证明复合胁迫可以改变单一胁迫下植物激素的调控机制。

Studying on Effect of Cd in Combination with UV-B on Physiological Mechanism in Regulation of Soybean Epicotyl Growth

It was investigated that the changes in levels of indole acetic acid (IAA) and gibberellins (GAs) in soybean epicotyl exposed to Cd,enhanced UV-B radiation and combination of Cd and UV-B radiation (Cd+UV-B).The levels of IAA and GAs and characteristics of epicotyl elongation under stresses have been analyzed.The results show that UV-B radiation could decrease elongation of epicotyl and increase its diameters;Cd stress has no obvious effect on epicotyl length.Obvious increase in epicotyl length and decrease in their diameters exposure to Cd+UV-B has been discovered.UV-B radiation caused significant decrease in IAA content and increase in GAs contents (P<0.05);Under Cd stress the changes in IAA and GAs levels was not obvious.UV-B radiation enhanced significantly activities of IAA oxidase and peroxidase (POD).Cd could suppress the UV-induced up-regulation of the IAA oxidase activity and keep higher level of IAA in epicotyl under Cd+UV-B,which may be the decisive causes of increase in elongation and decrease in diameter of epicotyl.Although UV-B radiation could lead to marked increase in GAs level,the changes in IAA level may be primary and direct reason of inducing changes in epicotyl growth.It also suggested that Cd+UV-B stress could change the hormones regulation abilities under stress of single factor.