Female gametophyte development in Eleocharis sellowiana (CYPERACEAE): a species with atypical nuclear staining and polarity of the megaspore mother cell

摘要

Megasporogenesis begins when one cell arising from the hypodermis of the nucellus differentiates into a megaspore mother cell. This cell undergoes meiosis, giving rise to a tetrad of megaspores, whose functional megaspore originates the megagametophyte. Representatives of the family Cyperaceae draw attention because both micro- and megasporogenesis culminate in the selection of a functional cell and the loss of the other three by programmed cell death after meiosis. We investigated in a more detailed manner the megasporogenesis and megagametogenesis in Eleocharis sellowiana Kunth using structural and ultrastructural tools. Although the megagametophyte of E. sellowiana is of the Polygonum type, we found some new features related to the megaspore mother cell, such as (1) absence of nuclear staining when exposed to toluidine blue and (2) presence of plastids and nucleus located at the micropilar pole, instead of the central region to the chalazal pole, as found in the literature for the Polygonum type. This opposite polarity could indicate that the cytoplasmic orientation in the megasporocyte is not a decisive event in the selection of the functional meiotic product for Polygonum type development.