Embryological studies on Trichloris (Poaceae, Chloridoideae)

Abstract

The present study provides information on the development of the female and male gametophytes and seed ontogenycharacteristics for Trichloris, and it discusses their taxonomic significance to the family Poaceae. Trichloris species are characterizedby having 2–3 stamens per floret, tetrasporangiate anthers, a monocotyledonous development of the anther wall, a single middlelayer of common origin with the tapetum, fibrous thickening in the cell walls of the endothecium, and a secretory tapetum. Thesecharacteristics are constant within Poaceae. The possession of bitegmic and tenuinucellate ovules, laterally positioned antipodals priorto their degeneration, a free exocarp, and an epiblast in the mature embryos gives Trichloris the typical characteristics described forother members of the subfamily Chloridoideae. The degradation of tapetal cells before the maturation of the pollen grain and theabsence of aborted ovules indicate a high fertility rate, which is an important feature for perennial halophytes such Trichloris that do notpossess elaborate seed dormancy systems.