Abstract: 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 clays after recovery. During the entire period of experiment (from o-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 o-time treatment, after 34 h treatment at 25℃, 3 and 6 days after chilling, and 3 days after recovery. Succinic dehydrogenase anct 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℃. 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 mitochondrial membrane.

Key words: corn, permeability of plasma membrane, leaf mitochondria, membranebound enzymes, mefluidide