CHLOROPLAST STRUCTURE AND PIGMENT COMPOSITION IN THE RED ALGA <i>GRIFFITHSIA PACIFICA</i>: REGULATION BY LIGHT INTENSITY¹

Abstract

SUMMARY The ratio of accessory phycobiliproteins to chlorophyll a is controlled by light intensity in the marine red alga Griffithsia pacifica. The greatest changes in pigment ratios are observed below 300 ft‐c; above 300 ft‐c the response approaches saturation. Ultrastructural examination of chloroplasts of plants grown at different intensities reveals that the number of phycobilisomes per unit of photosynthetic thylakoid changes in direct proportion to the pigment ratios and in inverse proportion to the light intensity.