Development of the Endosperm of Myrsine laetevirens (Myrsinaceae). I. Cellularization and Deposition of Cell‐Wall Storage Carbohydrates

Myrsine laetevirens has a nuclear type of endosperm development. Vacuole formation in peripheral coenocytic cytoplasm precedes cytokinesis and compartmentalizes the cytoplasm. Cellularization starts as a series of anticlinal walls projecting centripetally. Periclinal cell walls are formed from expanding cell plates following nuclear divisions. The developing walls are flanked by endoplasmic reticulum cisternae with dilated and short profiles and few ribosomes. Subsequent anticlinal wall growth and periclinal divisions elongate the endosperm into the central vacuole, resulting, finally, in the convergence of the advancing tissue. After that, the endosperm increases in size by anticlinal, periclinal, and oblique divisions in all cells of the endosperm and involving phragmoplast and cell plate. Carbohydrate deposition in the cell walls begins 40 d after pollination (DAP) with deposition of pectins in the cell layers next to the embryo. At ca. 50 DAP, the cell walls of the bulk endosperm begin to thicken, sho...