Morphogenesis of the sporoderm of Pollinia of Anoectochilus roxburghii

Abstract The pollen grains of Anoectochilus roxburghii aggregate in pollinia. The aim of this study was to analyse the structural characteristics of pollinium development in A. roxburghii. Features of the pollinia begin to form in the sporogenous cells, in which some cell walls begin to differentiate to form the outline of the pollinia. During development of the microspore mother cells (MMCs), the nucleus and organelles penetrate the cell walls (cytomixis) between MMCs within a pollinium, but not between the MMCs among different pollinia. A thick callose wall forms on the surface of the pollinia, but not between MMCs inside the pollinium. After meiosis, a sporopollenin exine forms on the surface of the pollinia, but not on the surface of pollen grains inside the pollinium. The mature pollen of A. roxburghii is bicellular and consists of a vegetative cell and a generative cell.