Non‐Enzymatic Reduction of Nitrite by Means of Ascorbic Acid in Citrus and Other Higher Plant Tissues

Abstract

It has been proved that the nitrite reduction in the leaves and other plant tissues of citrus and other green plants is partly or mainly a non‐enzymatic chemical process, and a heat‐stable factor present in these tissues is responsible for this reduction. It is suggested that ascorbic acid plays a major role in this chemical reaction since the reduction is inhibited by ascorbic acid oxidase. A significant association was also found between the ascorbic acid content and the nitrite reduction capacity of citrus leaves. Evidence has been presented that this non‐enzymatic chemical reduction of nitrite occurs also in vivo as undetached citrus leaves on branches placed in NaNO2 solution have shown diminution of their ascorbic acid content along with the absorption of nitrite. Stronger accumulation of nitrite in these leaf tissues was observed under dark conditions, apparently due to the inhibition of the biosynthesis of the ascorbic acid.