Premeiotic microsporocyte cell shape influences shape of tetrads during microsporogenesis

Angiosperm microspores are grouped into tetrads before they mature into functional pollen grains. This tetrad stage is an important step in microsporogenesis. Tetrad shapes are diverse across angiosperms, with high levels of variation sometimes occurring within species, reflecting variation in early developmental events of nuclear and cell division (i.e., meiosis and cytokinesis). Among these developmental influences, the shape of the microsporocyte (pollen mother cell; hereafter PMC) is likely to influence tetrad shape. This article presents a test of this hypothesis in 19 species of higher Asparagales with a successive cytokinesis by inferring PMC shape from tetrads observed with epifluorescence microscopy. Sampled species show differences in PMC shape between groups of regular or irregular tetrads at the species level, and there is a strong component of PMC shape variation at the onset of meiosis on resulting tetrad shape, with more elongated PMCs yielding significantly more irregular tetrads