Environmental Influences on Nitrite Reductase Activity inPisum sativumL. Seedlings

Although the effects of environmental changes on extractable nitrate reductase activity are well documented, little attention has been paid to the response of nitrite reductase to similar treatments. We have followed changes in the level of extractable nitrate and nitrite reductase in the leaves of pea seedlings subjected to different light, shade, drought, and nitrate treatments. In similarity to nitrate reductase, extractable nitrite reductase increases with availability of nitrate. However, it appears that the two enzyme activities show differential responses in plants exposed to drought conditions and in plants transferred to darkness. Nitrate reductase activity declines much more rapidly than nitrite reductase. These observations and the varying influence of the other environmental treatments are discussed in relation to the different cellular locations of nitrate and nitrite reductase.