CHANGES IN THE STRUCTURE, FUNCTIONAL-ACTI VITY, AND LIPID-COMPOSITIONOF CHLOROPLASTS DURING PROLONGED STORAGE AT LOW-TEMPERATURES

The conditions of the initiation of regular arrays of intramembranous particles on the exoplasmic fracture face (EF,) of thylakoid membranes during prolonged storage at 4-7 degrees C have been studied. The regu latory of particles takes place on the 5th-7th days of storage and cor related with the dedradation of membrane lipids and oxygenevolving act ivity of chloroplasts. Using thin-layer chromatography we found, that the intensity of MGDG and phospolipis bands reduced significantly, whe reas the intensity of DGDG band reduced slightly. New lipid bands appe ar, that probably represent the products of the polar membrane lipid h ydrolisis. As can be seen in thin sections of chloroplasts, large lipi d osmiophylic drops, often of irregular shape, are formed on the thyla koid edges under the storage conditions. The fraction of these drops w as isolated that consisted mainly of hydrolisis products. It has been suggested, that the drops are formed by the coalescing lipids from thy lakoid membrane during storage. The drops are composed of the aggregat es of cylindrical inverted micelles, that can be seen at fracture face s. The regularity of the particles disappears under nonstable storage conditions (mixing), and the particles are reduced in sizes, as compar ed to freshly isolated chloroplasts or chloroplasts stored under stabl e conditions. It is supposed, that the regularity of the intramembrano us particles, that are structural manifestation of the chlorophyll-pro tein complexes results from the considerable loss of lipids from thyla koid membranes and, therefore, alterations in the electrostatical surf ace potencial.