Mefluidide对提高玉米幼苗抗寒性的进一步研究

FURTHER STUDY OF THE MEFLUIDIDE-INDUCED CHILLING TOLERANCE IN CORN SEEDLINGS

玉米(Zea mays L.)三叶期用15ppm mefluidide喷洒叶面,24小时后移入5℃低环境中,6天期间,质膜外渗电导率无明显上升趋势。处理植株的叶片线粒体的膜琥珀酸脱酶和ATP酶活性,在25℃下测定,表现为5℃使3天后活性显著升高,而6天后下降,但对照下降幅度明显低。用mefluidide处理玉米于25℃环境中l天,叶片线粒体膜的ATP的温度折点比对照降低5℃左右,并在连续6天低温后,能保持线粒体膜ATP酶活性的温反应及低于对照的低温折点。证明mefluidide能提高作物抗寒性是与其影响生物膜结构功能有密切关系。

Corn seedlings (cv. Dandong 2), at 3 leaf-age, were foliar sprayed with 15ppm mefluidide and held at 25℃ regime for 24h. The seedlings were then chilled at 5℃ for 6 days, after which they were returned to the 25℃ regime for recovery. Leaf conductivity was done on plants at O time, just prior to chilling, 3 and 6 days after chilling, and 3 days after recovery. During the entire period of experiment (from 0-time to recovery), the conductivity of the treated plants was at a more or less constant level of 15%, Whereas the control increased from 15% to about 50% 6 days after chilling as well as well as 3 days after recovery. Our results strongly suggest that the treated plants were not injured during a 6-day chilling exposure, while the control was progressively injured. Mitochondria were isolated from plants at 0-time treatment, after 34 h treatment at 25℃, 3 and 6 days after chilling, and 3 days after recovery. Succinic dehydrogenase and ATPase were extracted from the mitochondria. Activities of both enzymes were measured at 25℃. There was a marked increase in activity of both enzymes in either treated plants or controls 3 days after chilling. However, the increase was significantly higher in the treated plants than those in the control. Activities were decreased at 6 days after chilling. The decrease in the control was significantly greater than those in the treated plants. ATPase activity was measured over a range of temperatures from 5° to 35℃. There were two distinguished break points on the Arrhenius plots for ATPase activation energy in the treated plants. One was at about 20℃ and the other was at about 10℃. However, the control only showed one break point at 15°C. There was a 5℃ difference between the control and treated plants. Albeit the significance of a 5℃ difference in activation of energy in terms of increased chilling tolerance is; debatable, it does suggest that mefluidide treatment may alter the property of corn mitochon-drial membrane.