Pollination is the process by which pollen is transferred to the female reproductive organs of a plant, which allows fertilization to occur. Like all living organisms, seed plants have a single main purpose: to pass on their genetic information to the next generation. The reproductive unit is the seed, and pollination is an essential step in the production of seeds in all spermatophytes (seed plants).
For the pollination process to be successful, a grain of pollen produced by the anther, the masculine part of a flower, must be transferred to a stigma, the feminine part of the flower, of a plant of the same species. The process is quite different in angiosperms (flowering plants) than it is in gymnosperms (other seed plants). In angiosperms, after the pollen grain has landed on the stigma, it creates a pollen tube that grows downward until it reaches the ovary. The spermatic cells of the pollen grain move along the pollen tube, enter the ovule through the micropile and fertilize it, which results in the production of a seed.
A successful angiosperm pollen grain (gametophyte) containing the male gametes is transported to the stigma, where it germinates and its pollen tube grows towards the ovary. Its two gametes travel through the tube to where are the gametophytes that contain the female gametes inside the carpel. One nucleus fuses with the polar bodies to produce the tissues of the endosperm, and the other with the ovum to produce the embryo. Hence the term: "double fertilization".
In gymnosperms, the ovum is not contained in a carpel, but is exposed on the surface of a dedicated support organ, such as the scale of a cone, so penetration of the carpel tissue is unnecessary. The details of the process vary according to the division of gymnosperms in question. Two main modes of fertilization are found in gymnosperms. Cycads and ginkgo have motile sperm that swim directly to the egg within the egg, while conifers and gneophytes have sperm that can not swim, but are transported to the egg along a tube of pollen.
The study of pollination brings together many disciplines, such as botany, horticulture, entomology and ecology. The pollination process as an interaction between the flower vector and pollen was first addressed in the 18th century by Christian Konrad Sprengel. It is important in horticulture and agriculture, because fruiting depends on fertilization: the result of pollination. The study of insect pollination is known as anthecology.
