Changes in Fine Structure of Prolamellar Body in Relation to the Formation of the Chloroplast

The formation of the prolamellar body was studied using the seedlings of Cucumis sativus in relation to the development of lamellar structure in the plastids. The seedlings were grown in the light for various lengths of time, and then transferred to darkness. The prolamellar bodies were formed in a plastid in the dark, and increased in number as the lamellar structure developed. The formation of prolamellar bodies in the plastid, in which the grana lamellae differentiate, seems to occur only in the region of intergrana lamellae. Besides, the present experiment showed that the prolamellar bodies in continuous dark are devoid of lamellar structure, and that they are also produced when the seedling is transferred to the darkness at its earlier stage of development. Moreover, the prolamellar body and lamellar structure are formed simultaneously under the weak light condition, while the former disappears under stronger light. From these observations, it is suggested that the appearance of prolamellar body may be caused by blocking the conversion of vesicles into lamellae.