ELECTRON-MICROSCOPY OF THE RESERVES MOBILIZATION IN GERMINATING COMMON BEAN (PHASEOLUS-VULGARIS L.) SEEDS

The ultrastructure of the reserves mobilization in common bean cotyled on parenchyma cells during germination was investigated using scanning and transmission electron microscopes. At the first germination stage , the ultrastructural changes in cotyledon parenchyma cells were obser ved with the formation of small vacuoles from the protein bodies (abou t 5 mu m in diameter). These vacuoles developed to large vacuoles by f using with each other. Large vacuoles were surrounded by developed rou gh endoplasmic reticulum (RER) and high electron-dense vesicles. Durin g the middle germination stage, most of the parenchyma cells were fill ed with large vacuoles, and these cells had numerous high electron-den se vesicles and small vesicles. By observation with a transmission ele ctron microscope, starch grain breakdown rapidly proceeded in amylopla sts from the middle germination stage. Additionally, the young plastid s had small starch grains, and few inner membranes were observed durin g the middle germination stage. By the last germination stage, starch grains became smaller and eventually disappeared, and the young plasti ds progressed into mature chloroplasts. From the observations by scann ing and transmission electron microscopes, the developed RER system, d eveloped large vacuoles and numerous small vesicles seem to be closely related to the protein breakdown during the germination of common bea n seed. In addition, starch breakdown proceeded to the last from the m iddle germination stage. The newly formed plastids with developed inne r membranes were observed in the cotyledon with starch breakdown.