Pollination is the transfer of pollen from the stamen to the pistil of a flower. Fertilization is the union of the female reproductive cell in the ovary with the male germ cell from the pollen grain. Fecundity is the fruitfullness or productiveness of the flower; in economic biology, it describes the percentage of seed set or fruit development.
Nature has provided several methods to pollinate and fertilize plant flowers (Figure 1). The simplest of these is self-pollination, whereby pollen from a flower pollinates and fertilizes the ovules of the same flower. Sometimes selfpollinated plants do not require any outside assistance from wind or bees for complete pollination. But in other selfpollinated plants, these agents ( bees and wind ) are needed to move the pollen about. In the second example, the pollen is transferred from one flower on a plant to another flower on the same plant. This is necessary in many of the vine crops such as cucumbers where male flowers produce only pollen and female flowers have only the pistil. Bees, particularly honey bees, are essential for cucumber pollination. A third method is transfer of pollen from a flower of one plant to a flower of another. This is important in crops such as apples, where trees of a certain variety cannot be pollinated by flowers of the same variety due to pollen incompatibility. Because vegetatively propagated trees of the same variety are genetically the same, and the flowers self-sterile, different varieties must be interplanted to provide compatible pollen for pollination.
In any pollination work, it is important to know which of these three pollination methods is involved to provide adequate pollination.
There are many agents of pollination other than bees. Pines and some other trees, grasses, and some weeds are pollinated by wind. Such plants produce a very large number of relatively small pollen grains, easily carried by air currents. Insect pollinated plants produce large pollen grains but usually in smaller numbers. Insect pollinated flowers are usually showy - having evolved from the need to attract insect pollinators. However, many wind pollinated flowers such as maple, oak, hickory, corn, and ragweed are visited by bees collecting pollen.
Insects other than bees visit flowers and serve as pollinating agents, too. Flies, wasps, beetles, butterflies moths, and other insects work flowers for pollen and/or nectar and help pollinate those flowers. Usually they are of little or no value to economic crops.
Some animals, including hummingbirds and even bats, pollinate flowers. None of these are important in Ohio's agriculture.
Of all the types of bees, honeybees have several advantages as pollinators. They are relatively abundant and manageable. Bees from a colony will visit a large number of plants over a large area, collecting pollen and nectar, with individual bees visiting one species of flowers in the same location until the supply of nectar or pollen is exhausted. This loyalty or constancy is not found in some other social bees, which visit different plant species during the same trip in the fields. This indescriminate behavior reduces the effectiveness of the bee species as a pollinator because the pollens are mixed.
Honeybees have numerous adaptations helpful to them for effective pollination. Some of the more important ones are:
(1) Social unit: Because the entire colony overwinters, large numbersof bees are ready to forage in early spring, as compared to other bees such as the bumble bee, where only the queen overwinters.
(2) Forked body hairs: These hairs enable the bee to pick up pollen and move it around better than insects with simple, unforked hairs, or insects without any body hairs.
(3) Corbiculae - the pollen basket: Pollen baskets are structures on the hind legs of worker honeybees which allow these bees to carry pollen back to the colony.
(4) Antennae cleaner: This is a structure on the front legs, which enables the bee to clean the antennae.
(5) Communication from bee to bee: By dancing, and other specialized systems of communication, scout bees can transmit information about a crop to other bees, thus greatly improving pollination activity.