Growth of grana from “primary” thylakoids in Phaseolus vulgaris

• Published in: Plant and cell physiology 1976-10, Vol.17 (5), p.939-954
• Main Authors: Argyroudi-Akoyunoglou, J. H., Kondylaki, S., Akoyunoglou, G.
• Format: Article
• Language: English
• ISSN: 0032-0781; 1471-9053; 1471-9053
• DOI: 10.1093/oxfordjournals.pcp.a075368

The plastids of young dark-grown bean leaves, exposed to periodic light are agranal, devoid of chlorophyll b and contain primary thylakoids and chlorophyll a. Transfer of these plants to continuous illumination results in synthesis of new chlorophyll a, chlorophyll b and grana. This study was done in order to study whether and how the grana are formed from preexisting primary thylakoids. 14C-δ-aminolevulinic acid was used to label the chlorophyll a of the primary thylakoids, and its fate was studied after transfer of the plants to continuous light. It was found that chlorophyll b and grana become 14C-labelled. The total radioactivity of chlorophyll b per bean increased with the parallel decrease of that of chlorophyll a. All subchloroplast fractions, obtained after digitonin disruption of chloroplasts, contained chlorophyll a of equal specific radioactivity. The specific radioactivity of chlorophyll b was lower than that of chlorophyll a, and, in addition, it was lower in the grana than in the stroma lamellae fraction. The data suggest that chlorophyll b is formed from chlorophyll a; the grana are formed by stacking of preexisting primary thylakoids; chlorophyll b is synthesized faster in the grana than the stroma lamellae; the newly formed chlorophyll a molecules are distributed at random throughout the developing photosynthetic membrane and not on specific growing sites.