This purchase only includes chapter 16 of this title.
Abstract
Megagametophyte maturation in gymnosperms includes nutrient storage and embryo development. In the living Cycadales starch is accumulated before fertilization. Here starch accumulation by the megagametophyte is related to cellularization, archegonia development, fertilization, and embryogeny. Megastrobili, ovules, and seeds were collected from their natural localities and fixed in FAA. Starch was detected using histochemical staining with IKI and PAS. Embryos appeared two years after megastrobilus emergence in Ceratozamia mexicana and one year after this event in Zamia furfuracea. Starch grains in both species were structurally similar, but there were differences in the rate of formation. This accumulation of starch was not related to embryo development. During cellularization and differentiation of archegonia, few starch grains were observed. Later the starch grains were arranged toward the periphery of the cells and increased in size. Before dispersal, but when the archegonia were mature, starch grains were abundant.
