Environmental Influences on Nitrite Reductase Activity in Pisum sativum L. Seedlings

Although the effects of environmental changes on extractablenitrate reductase activity are well documented, little attentionhas been paid to the response of nitrite reductase to similartreatments. We have followed changes in the level of extractable nitrateand nitrite reductase in the leaves of pea seedlings subjectedto different light, shade, drought, and nitrate treatments.In similarity to nitrate reductase, extractable nitrite reductaseincreases with availability of nitrate. However, it appearsthat the two enzyme activities show differential responses inplants exposed to drought conditions and in plants transferredto darkness. Nitrate reductase activity declines much more rapidlythan nitrite reductase. These observations and the varying influence of the other environmentaltreatments are discussed in relation to the different cellularlocations of nitrate and nitrite reductase. Key words: Environmental responses, Nitrate reductase, Nitrite reductase