protochlorophylln.

1894 Jrnl. Royal Microsc. Soc. 702 The same author [sc. Monteverde] finds, in etiolated leaves, besides xanthophyll and carotin, a pigment to which he gives the name protochlorophyll. It displays a distinct red fluorescence.

1928 Science 7 Dec. 570/2 Protochlorophyll is not a decomposition product of some other organic substance, as leucophyll, but is a pigment which develops without the influence of light and changes photochemically into chlorophyll upon exposure to light.

1951 Ann. Rev. Plant Physiol. 2 131 Protochlorophyll is a pale greenish pigment containing two hydrogen atoms less than chlorophyll.

1989 B. Alberts et al. Molecular Biol. Cell (ed. 2) xx. 1162 When exposed to light, the etioplasts rapidly develop into chloroplasts by converting protochlorophyll to chlorophyll.