How Does a Pollen Grain Get to the Stigma of a Pistil?
Pollination is the process by which pollen is transported from the anthers to the stigma of a flower or plant. Some plants have the ability to self-pollinate as pollen falls off of the anther and lands on the stigma. Most plants benefit from cross-pollination.
In nature cross-pollination generally occurs by wind and animals.
corn image by Cathy Kovarik from Fotolia.com
Some plants produce lightweight pollen which enables the wind to carry pollen grains from one plant to the next. The sticky surface of the stigma traps the pollen. Farmers will generally facilitate wind pollination by planting crops, such as corn, close together.
bee image by Tatjana Gupalo from Fotolia.com
Birds and insects play a vital role in pollination. The deliberate colours and fragrances of some flowers attract pollinators with the promise of food. A familiar example of a pollinator is the bee who travels from flower to flower feeding on nectar and pollen. While the bee is feeding pollen sticks to the bee and gets carried to the next flower. This method of pollination increases the variation within a plant species and improves it chances for survival.
While most flowers rely on petal colour and fragrances to successfully lure birds and insects, other flowers use mimicry to attract animals. An example of this is an Australian orchid, Chiloglottis trapeziformis, which releases the scent of a female wasp. The male wasp unknowingly carries pollen from flower to flower as he searches for a mate.