Seedlings of Plantago insularis were grown in darkness for 5 days and then exposed to white light for 24 h. At the beginning of the light period some plants were treated with thiamine pyrophosphate (TPP). Light exposure caused a marked development of both chlorophyll a and b in the normal (al+/al+) plant, but only a slight formation of chlorophyll in the mutant (al/al) TPP plus light induced the formation of chlorophyll a and b in the mutant to near normal levels. Light alone increased the level of carotenoids in the normal type, but not in the mutant; but TPP plus light increased the carotenoids in the mutant to near normal. Albinism in Plantago is due, in part, to a deficiency in TPP and a consequent deficiency in chlorophyll and carotenoid pigments.
Acid-soluble nitrogen was distinctly lower in the albino mutant than in normal plants, but increased in the mutant after treatment with TPP and exposure to light. Exposure of dark-grown normal seedlings to light alone caused a marked increase in acid-insoluble nitrogen. Recovery in the mutant appeared to be at the expense of the soluble nitrogen fraction, and is attributed to the synthesis of chloroplast proteins. The light-yellow mutant grown in the dark became bleached on exposure to light, yet a moderate increase in nitrogen occurred during exposure, indicating that some protein synthesis is independent of chlorophyll and carotenoid development in the plastids. A pathway initially involving TPP appears to be affected by light in the formation of chloroplast proteins.