Pollination is very important for plants as they help in plant reproduction. Only seed bearing plants produce what is called pollen. Pollen is a fine powdery substance yellow or orange in color. It is discharged from the flowers of male plants. The pollen grains contain male reproductive cells (called gametes) and are capable of fertilizing the female reproductive cells to which it gets transported in multiple ways. The transfer of pollen grains from the male part of the plant called stamen to the female part called pistil is called pollination.
Pollination may be self-pollination or cross-pollination. When the pollen travels to the pistil of the same plant, it is self pollination and when it travels to pistil of another plant, it is cross-pollination. Wind, rain drops, birds, insects and some animals act as pollinators by carrying the pollen to other plants involuntarily. The pollen is light weight and could easily be carried long distances by the wind.
In flowering plants, the ovules are enclosed within the pistil. When a pollen grain lands on a receptive stigma, a pollen tube grows down through the style until it reaches an ovule. There it releases a sperm cell that fertilizes an egg cell and the ovule eventually matures into a seed.
Honey bees, beetles, bumble bees, wasps, flies, butterflies, bats and birds play an important role in pollination by picking up pollen as they probe for nectar. Food is what insects and other creatures receive in exchange for their services as pollinators. While some eat the pollen, others feed on the nectar secreted by special glands that are hidden deep within the blossom. Any visitor to the plant receives some amount of pollen as it looks for food and unknowingly transfers it to other plants while it moving to the next flower it visits. Pollination by wind may or may not be successful. Plants relying on it must produce an enormous amount of pollen for increasing the rate of success.
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