Pollen cell. In flowering plants the vegetative tube cell produces the pollen tube, and the generative cell divides to form the two sperm cells. Pollen is produced in the microsporangia in the male cone of a conifer or other gymnosperm or in the anthers of an angiosperm flower. Pollen grains come in a wide variety of shapes, sizes, and surface markings characteristic of the species (see electron micrograph, right). Pollen grains of pines, firs, and spruces are winged. The smallest pollen grain, that of the forget-me-not ("Myosotis" spp.), is around 6 µm (0.006 mm) in diameter. Wind-borne pollen grains can be
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