Pollination occurs in several different ways, depending on the structure of
Plants that self-pollinate are called selfers. For example, the reproductive
structures of pea flowers are enclosed between two fused petals, called a
keel, which ensures that self-fertilization takes place.
Wind-pollinated plants, such as trees and grasses, generally produce
large amounts of small, light pollen that is not sticky. The flowers are not
usually colorful, do not produce nectar, and have no odor. The flowers form
before the leaves do and the stamens and stigmas are exposed to the wind.
When these flowers are blown about by the wind, the pollen shakes loose
from the anther of one plant and is deposited on the stigma of another
plant. Most pollen can be carried up to 330 feet (100 meters) from the
plant. These types of flowers are usually found in temperate regions and
are rare in the tropics.
|Figure 3.2 A butterfly uses its proboscis
to suck nectar from a thyme flower.
Insect pollinators pick up pollen grains as they feed on nectar from one
plant and deposit it on subsequent plants that they visit. The flowers pollinated
by insects tend to have sticky pollen that adheres to the hairs on
the legs of the insects. There are approximately 20,000 species of bees
attracted to sweet-scented flowers that produce nectar and 16 families of
beetles that are lured to flowers with fruity, spicy, or pungent odors. Flies also pollinate flowers as they feed. Butterflies have a long, thin proboscis to
suck nectar from tubular flowers or flowers with a long style, but the pollen
tends not to stick to their bodies and so they are not efficient pollinators