Temperature effect on nitrate reductase activity in vivo

Temperature effect on the in vivo activity of nitrate reductase in barley leaf strips following 2-min treatment was studied. Exposures to temperatures above 20°C brought about an increase in the in vivo activity. The most effective temperature was 45°C, which caused a 3-4 fold increase of activity. The enhancing effect of the treatment at 45°C was largely reversible by an immediate consecutive 2-min treatment at low temperature, and vice versa. The enhancing effect was also found to revert back to normal during 2-h incubation period at room temperature. The significance of these findings with respect to the regulation of nitrate reductase activity is discussed.