Ultrastructure of fusion product between protoplasts from C3 and C4 species of amaranthaceae

This paper describes the ultrastructure of the electric field-induced fusion products of C3 and C4 species of Amaranthaceae at the early developmental stage. Protoplasts of C3 species were isolated from a Celosia cristata L. cell suspension and, those of C4 species were isolated from an Amaranthus tricolor L. cotyledon. Incompatibility occurred in the C3/C4 hybrid. The incompatibility reactions were detected in the newly formed hybrid cells accompanied with significant changes in the nucleolus (segregation of nucleolar components) and plastids (cup-like shape or amoeboid plastid enclosing cytoplasmic materials) of G3 species parent. The structural changes in the organelles of the C4 partner were less marked. After 5 days of culture, most organelles showed high cellular activity, and a normal dedifferentiation process of mesophyll chloroplasts was observed. At this stage nucleolar segregation was not detected and the C3 species plastids were difficult to distinguish from the proplastids formed from mesophyll chloroplasts. In addition, some mitochondria showed bursting-like structure. However, under the culture condition used these somatic incompatibility did not seem to impair further growth of fusion products since they were still proliferating well resulting in callus formation.