[Plastoglobuli in different types of plastids from Allium cepa L]

Abstract

The occurence and size of plastoglobuli were studied in the different types of plastids from Allium cepa. The function of plastoglobuli as a reservoir for lipoquinones is discussed. 1. The white turgescent leaves of the onion contain chloroplasts in the cells close to the vascular bundles. These chloroplasts show the usual thylakoid arrangement and possess numerous plastoglobuli (av. diameter 65 nm). There also exist plastid-like components with concentrically arranged membranes and osmiophilic lipid inclusions (av. diameter 200 nm). 2. The chloroplasts in green sprouting leaves contain less and smaller plastoglobuli (diameter ca. 45 nm). 3. The plastoglobuli from leucoplasts possess the same size as plastoglobuli from chloroplasts in the onion leaves. The leucoplasts of the epidermis cells contain, however, less plastoglobuli than leucoplasts of the onion mesophyll. 4. The lipoquinone content in chloroplasts from green parts of the white turgescent onion leaves is much higher than in chloroplasts from green sprouting leaves. The concentrations of plastoquinone 45 are 25 X, of \ga-tocopherol 21 X, of \ga-tocoquinone 3,7 X and of vitamin K1 2,5 X higher with reference to chlorophyll a. 5. There is a direct correlation between lipoquinone and plastoglobuli content of plastids.