Ultrastructural Analysis of Cell Wall Formation and Cell Division of Soybean Protoplasts

Abstract

Protoplasts of soybean (Glycine max (L.) Merr.) were isolated from suspension cultures and morphological changes during culture were observed using transmission electron microscopy. The regeneration of cell walls on the surface of the protoplasts was accompanied by the release of smooth vesicles from cytoplasm to the outside plasma membrane. The vesicles were presumed to carry some wall materials from cytoplasm for cell wall formation. With the elapse of time, the wall materials were gradually deposited and a complex cell wall layer was formed 2-3 d after culture. The fine structure of cellulose microfibrils was clearly observed about 3 d after culture using a polysaccharide staining procedure. During the cell wall formation, numerous smooth vesicles were always found between the plasma membrane and newly synthesized cell wall. Nuclear division and subsequent cytokinesis were observed about 1 d after culture. From the results obtained by the present and previous researches, it may be concluded that cell wall formation usually starts earlier than cell division and then both reactions proceed concurrently and that smooth vesicles play an important role in cell wall formation.