Development of Microspores-digieduco

Development of Microspores: Microspores or pollen grains are developed within the microsporangia i.e. anther lobes of the stamen.

A very young anther is made up of homogeneous meristematic cells and more or less oblong in shape. Gradually the anther becomes a four-lobed structure, in each lobe hypodermal cells become differentiated by their shape and dense contents with distinct nucleus, these cells are called archespon'um or archesporial cells.
Next archesporial cells divide to form an outer primary partietal cell layer and an inner primary sporogenous cell layer. Cells of primary parietal layer divide pen'clinally and anticlinally giving rise to several cell-layered anther wall, while cells of the primary sporogenous layer either function directly as spore mother cells or may divide further to form more cells which function as spore mother cells. Innermost layer of wall-cells over the sporogenous tissue functions as nutritive layer, called tapetum. Each spore mother cell by two divisions (of which first one is reduction division i.e. meiosis) gives rise to four haploid (n) nuclei arranged tetrahedrally-these nuclei are then surrounded by cell walls and form microspores i. e. pollen grains