EARLY ENDOSPERM DEVELOPMENT IN OVULES OF SOYBEAN, GLYCINE-MAX (L) MERR (FABACEAE)

Endosperm development was studied in normally setting flowers and pods of soybean from anthesis to a pod length of 10-20 mm. The free-nuclear stage following double fertilization is typified by loss of starch and increasing vacuolation. The cytoplasm provides evidence of extensive metabolic activity. Wall ingrowths, already present at the micropylar end of the embryo sac wall prior to fertilization, develop along the lateral wall of the central cell as well as at the chalazal endosperm haustorium. Endosperm cellularization begins when the embryo has developed a distinct globular embryo proper and suspensor. Cellularization starts at the micropylar end of the embryo sac as a series of antidinal walls projecting into the endosperm cytoplasm from the wall of the central cell. The free, growing ends of these walls are associated with vesicles, microtubules, and endoplasrnic reticulum. Pendinal walls that complete the compartmentalizalion of portions of the endosperm cytoplasm are initiated as cell plates formed during continued mitosis of the endosperm nuclei. Endosperm cell walls are traversed by plasmodesmata. This study will provide a basis for comparison with endosperin from soybean flowers programmed to abscise. © 1992 Annals of Botany Company.