Shaked, A., Division of Citriculture, Volcani Center, Bet Dagan, Israel
Bar-akiva, A., Division of Citriculture, Volcani Center, Bet Dagan, Israel
Mendel, K., Division of Citriculture, Volcani Center, Bet Dagan, Israel

Evidence is presented for the presence of nitrite reductase in citrus leaves. The enzyme has a Km for nitrite of 45 mu and is inhibited by cyanide. However, unlike citrus nitrate reductase (l), it is probably not a metalloflavo protein, although it may be related to iron.In addition to the enzymatic nitrite reduction, non-enzymatic nitrite reduction was present in citrus leaf preparations. Under in vivo assay conditions nitrite reduction in one-month-old leaves was not inhibited by cyanide, in contrast with three-month-old leaves in which nitrite reduction was almost completely inhibited. Thus it appears that in very young citrus leaves most of the nitrite reduction is non-enzymatic. © 1973 Oxford University Press.