Chemical Regulation of Plastid Development. II.* Effect of CPTA on the Ultrastructure and Carotenoid Composition of Chromoplasts of Capsicum annuum Cultivars

Abstract

Electron microscopy of the fruit of three C. annuum cultivars, two with red fruit and one with yellow, showed that the chromoplasts of each cultivar contained fibrils, although carotenoid distribution of the red cultivars differed greatly from that of the yellow cultivar. The fibrils had a microfibrillar ultrastructure.

The chloroplast-chromoplast transformation in C. annuum fruit as well as the carotenoid distribution were affected by 2-(4-chlorophenylthio)ethyldiethylammonium chloride (CPTA). The synthesis of capsanthin and capsorubin, which are responsible for the colour of the red cultivars, was inhibited. The level of β-carotene was reduced in all three cultivars, accompanied by the accumulation of lycopene, γ-carotene and neurosporene. Chromoplasts of CPTA-treated fruit lacked fibrils but contained plastoglobuli. The inhibition of fibril formation at an early stage was interpreted as evidence for the genesis of fibrils from plastoglobuli. It seems likely that fibril formation is under separate genetic control, independent of carotenoid synthesis.

* Part I, Aust. J. Plant Physiol., 1974, 1, 119–33.