Pollen as large as about 90–100 µm. In angiosperms, during flower development the anther is composed of a mass of cells that appear undifferentiated, except for a partially differentiated dermis. As the flower develops, four groups of sporogenous cells form within the anther. The fertile sporogenous cells are surrounded by layers of sterile cells that grow into the wall of the pollen sac. Some of the cells grow into nutritive cells that supply nutrition for the microspores that form by meiotic division from the sporogenous cells. In a process called microsporogenesis, four haploid microspores are produced from each diploid sporogenous cell
Pollen tube This is a gene level regulation in which gene loci of the gynoecium allow either self pollen to slowly grow, stop growing or burst while faster growth of outcrossed pollen occurs, increasing genetic diversity. The main component is that this step determines which pollen grains are compatible to grow and parts of the style, and female embryo contribute in determining. Using hybrid species and crossing pollen, the interaction with the style and pollen was found to influence growth of the pollen tube based on compatibility. Pollen tube growth begins from when the pollen attaches to the stigma. It is followed