PLASTID DEVELOPMENT IN PRIMARY LEAVES OF PHASEOLUS VULGARIS

Abstract

SummaryFor 14‐day‐old dark‐grown beans a quantitative study of plastid membrane formation has been made for light‐induced chloroplast development in the primary leaves. During the first 10 h of illumination, thylakoid formation resulted from the rearrangement of the membranes of the prolamellar body. De novo thylakoid formation commenced between 10 and 15 h after the beginning of illumination and resulted, in the course of 160 h of illumination, in a ten‐fold increase in thylakoid membrane. During the course of greening no cell division occurred in the mesophyll cells, plastid expansion took place in all of the mesophyll cells but plastid division only occurred in the spongy mesophyll cells to result in an 11 % increase in the plastid number of the whole leaf during the first 18 h of illumination.When leaves were supplied with d‐threo‐chloramphenicol during greening there was a severe inhibition of thylakoid formation, vesicles were formed in the plastid stroma and rather fewer and larger grana than normal were produced. However, the proportion of thylakoid material in grana was normal. As l‐threo‐chloramphenicol yielded exactly normal chloroplasts it is concluded that thylakoid synthesis was inhibited by d‐threo‐chloramphenicol by the inhibition of the synthesis of one or more thylakoid proteins on the 708 ribosomes of the plastids.