Pollination

April 15, 2010 by  


ibn tufail 4-12-10

Pollination is the process by which pollen is transferred in plants, thereby enabling fertilization and sexual reproduction. Pollen grains, which contain the male gametes (sperm) to where the female gamete(s) are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself. The receptive part of the carpel is called a stigma in the flowers of angiosperms. The receptive part of the gymnosperm ovule is called themicropyle. Pollination is a necessary step in the reproduction of flowering plants, resulting in the production of offspring that are genetically diverse.

The pollination process as an interaction between flower and vector was first addressed in the 18th century by Christian Konrad Sprengel. It is important in horticulture and agriculture, because fruiting is dependent on fertilisation, which is the end result of pollination

Abiotic pollination refers to situations where pollination is mediated without the involvement of other organisms. Only 10% of flowering plants are pollinated without animal assistance. The most common form, anemophily, is pollination by wind. This form of pollination is predominant ingrasses, most conifers, and many deciduous trees. Hydrophily is pollination by water and occurs in aquatic plants which release their pollen directly into the surrounding water. About 80% of all plant pollination is biotic. Of the 20% of abiotically pollinated species, 98% is by wind and 2% by water.

More commonly, the process of pollination requires pollinators: organisms that carry or move the pollen grains from the anther to the receptive part of the carpel or pistil. This isbiotic pollination. The various flower traits that differentially attract one type of pollinator or another are known as pollination syndromes.

There are 200,000 varieties of animal pollinators in the wild, mostly insects. Pollination by insects often occurs on plants that have developed colored petals and a strong scent to attract insects such as bees, wasps and occasionally ants, beetles, moths and butterflies, and flies. In Zoophily, pollination is done by vertebrates such as birds and bats, particularly, hummingbirds, sunbirds, spiderhunters, honeyeaters, and fruit bats. Plants using bats or moths as pollinators typically have white petals and a strong scent, while plants that use birds as pollinators tend to develop red petals and rarely develop a scent (few birds have a sense of smell).

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