Protochlorophyllide

Protochlorophyllide, or monovinyl protochlorophyllide, is an immediate precursor of chlorophyll a that lacks the phytol side-chain of chlorophyll. Protochlorophyllide is highly fluorescent; mutants that accumulate it glow red if irradiated with blue light. In Angiosperms, the last step, conversion of protochlorophyllide to chlorophyll, is light-dependent, and such plants are pale (chlorotic) if grown in the darkness. Gymnosperms, algae, and photosynthetic bacteria have another, light-independent enzyme and grow green in the darkness as well.