Sexual reproduction of angiosperms is associated with the flower. Its most important parts are stamens and pistils. Complex processes of sexual reproduction take place in them – pollination and fertilization.
Pollination is a process during which pollen from the anthers of the plant’s stamens is transferred to the stigma of the pistil.
There are two ways to pollinate:
1. during self-pollination, pollen from the stamens of a flower falls on the stigma of the pistil of the same flower.
This is how oats, wheat, barley, beans, peas, and cotton are pollinated.
Self-pollination most often occurs before the blooming of the flower (in the bud). There are plants that do not bloom at all.
2. With cross-pollination, pollen from the stamens of one flower is transferred to the stigma of the pistil of another flower.
Cross-pollination can occur between different flowers of the same plant or different plants.
Cross-pollination is done with the help of wind, insects, water, birds.
* Pollination by wind. Signs of wind-pollinated plants
Poplar, alder, oak, birch, hazel, rye, corn and other plants are pollinated by the wind.
Wind-pollinated plants often grow in large clusters, for example, hazel thickets, birch groves, oak groves.
Most trees, whose flowers are pollinated by the wind, bloom in the spring, before the leaves open.
In plants, the pollen of which is carried by the wind, flowers are small, mostly without a perianth, often collected in inflorescences. Such flowers usually have anthers on long hanging filaments, very small, light, dry pollen. A lot of pollen is formed, but most of it does not fall on the stigmas of the pistils. The figure shows how male flowers, collected in earring inflorescences, sway in the wind and scatter pollen.
* Pollination with insects. Signs of insect pollinated plants
Insect pollination is the most common method of pollination in nature. Insects, feeding on nectar and pollen secreted by plants, fly around many plants to provide themselves with food, while simultaneously transferring pollen from one flower to another on their body.
To attract insects, plants have developed special adaptations: large single flowers or small flowers collected in inflorescences, bright color of petals or leaves of a simple perianth, the presence of nectar and aroma.
Large, sticky, rough pollen of flowers of such plants adheres well to the shaggy body of the insect.
During flowering, hives with bees are brought to the gardens. Bees pollinate the flowers of fruit trees in search of food, and the fruit yield increases.
Tropical plants can be pollinated by birds.
Pollen from aquatic plants can be carried by water.