Photoreduction of protochlorophyllide a to chlorophyllide a that is catalyzed by NADPH-protochlorophyllide oxidoreductase (NPR) is only a light-dependent step in overall processes of biosynthesis of Chl in angiosperms. Unlike many other plants, in fully green leaves of cucumber the expression of only a single NPR gene of cucumber was positively regulated by light and developmental age of leaf, and also by diurnal and circadian rhythms. The single NPR gene was shown to be involved in Chl synthesis throughout of the vegetative growth of cucumber (in cotyledons and fully green leaves).