Differentiation of Intracapsular Cells in the Sporophyte of Sphaerocarpos Donnellii

Abstract

Ultrastructural and histochemical changes during intracapsular cell differentiation in the premeiotic sporophyte of the liverwort Sphaerocarpos donnellii Austin were studied. From an initially undifferentiated meristematic tissue, spore mother cells and nutritive cells become differentiated. The first indications of ultrastructural differentiation into two cell types are the accumulation of lipid within spherosomes and the occurrence of plastid tubules in the presumptive spore mother cells. Once differentiated the two cell types are clearly distinguishable on the basis of cytoplasmic vacuolation, stored food reserve, and cell and nuclear size. The mature spore mother cell contains many spherosomes, small vacuoles, starch‐containing plastids, and a large central nucleus. The mature nutritive cell, on the other hand, is extremely vacuolate and contains large, starch‐filled plastids, a few spherosomes, and a small nucleus. A previously undescribed type of cell was observed in developing sporophyte capsules. This cell is located peripherally in the capsule and degenerates during differentiation of spore mother cells and nutritive cells.

Tapetum

“…In gymnosperms, the tapetal cells are comparatively long lived and can persist up to 6 months (Cecich 1984). In pteridophytes too, the life span of tapetal cells differs from a few days to few weeks (Kelley and Doyle 1975;Mogensen 1978).…”