The Stages of Gametophyte and Sporoderm Development in Pollen Grains

Resumo

Based on several modern plant species (Aristolochia clematitis, A. manshuriensis, Alliaria petiolata, Chloranthus japonicus, Symphytum officinale, Ambrosia trifida, Polemonium caeruleum, Plantago major, Populus tremula and P. × berolinensis), grown in botanical gardens of Moscow and Saint Petersburg, the stages of gametophyte and sporoderm development were compared. The most common regularities in the development of male gametophyte and its sporoderm were revealed. It is shown that the thicker the endexine, the later the intine starts to develop. The formation of tubular intine at the first mitosis of male gametophyte can occur after initiation of the intine, as it is observed in spores with endosporous spore germination in gametophyte. The dehydration of a pollen grain that is expressed in deposition of lipids and starch can start before the maturation of sporoderm that is observed in inaperturate pollen grains. Angiosperms show the broadest possibilities of variability in the sporoderm structure without losing the capacity for reproduction.