Abstract: Electron microscope observation revealed that mitochondria in plumular root cells of soy bean seed were invisible at the beginning of seed germination. They were sequentially formed re-differentiated and developed from proplastids during the process of germination. The proplastids in the control plumular root markedly expanded at low temperature imbibition process and did not develop into mitochondria when normal temperature was restored. Even the structure of reticulata membrane was further destroyed and vacuolized. In contrast, mitochondria of soybean seed pretreated with polyvinyl alcohol (PVA) and polythylene glycol-6000 (PEG) continused to develop well under the same conditions, as characterized by a clear structure of bilayered membrane and tube cristae. The results suggest that continuous re-differentiation and development of proplastids into mitochondria at low temperature imbibition process play an important role in the increase of soybean seed vigour and its resistance to chilling injury.

Key words: Polythylene glycol, Polyvinyl alcohnl, Development of mitochondria, Low temperature imbibition, Soybean seed