PARTICLE REGULARITY ON THYLAKOID FRACTURE FACES IS INFLUENCED BY STORAGE-CONDITIONS

Specific temperature, storage times, and medium composition enable ini tiation of regular arrays of intramembranous particles on the exoplasm ic fracture face during prolonged storage of isolated chloroplasts at 4 degrees C, producing about 2-10 regular arrays with 2-30 particles i n each array, with a period of about 36 nm, oriented in 1-4 directions . The particle sizes do not change throughout the time of storage (1-4 weeks). The second type of particle regularity arises during prolonge d storage of chloroplasts in greater than 1 M sucrose at -18 degrees C . Rounded areas of small particles tightly packed into paracrystalline arrays are found among less densely packed particles. The density of small particles is 4700 particles/mu m(2), and the mean size is 11 nm, whereas the particle density of the background is 1600 particles/mu m (2) with a mean particle size of 13 nm compared with 1200 particles/mu m(2) and mean size 16 nm in fresh chloroplasts. Based on the reductio n of particle sizes and manner of packing on the fracture face, it is proposed that the small particles are a light-harvesting complex, sepa rate from photosystem II and aggregated into paracrystalline arrays. T he thylakoid lipids may participate in formation of particle regularit y.