Pollination of plants: description, features, stages and types

The ultimate goal of a typical flower is the formation of fruits and seeds. This requires two processes. The first is pollination of plant flowers. After it occurs the actual fertilization - there are fruits and seeds. Let us further consider what are the types of pollination of plants.

General information

Pollination of plants - stage, which carries the transfer of small grainswith stamens on stigma. It is closely connected with another stage of development of cultures - the formation of the organ of reproduction. Scientists have established two types of pollination: allogamy and autogamy. The first can be carried out in two ways: by geytonogamy and xenogamy.

Characteristics

Autogamy - pollination of plants by transferring grains from the stamens to the stigma of oneorgan of reproduction. In other words, one system independently carries out the necessary process. Allogamy is the cross-transfer of grains from the stamens of one organ to the stigma of the other. Geytonogamiya assumes pollination between the flowers of one, and xenogamy - of different individuals. The first is genetically similar to autogamy. In this case, only recombination of gametes occurs in one individual. As a rule, such pollination is typical for multiflorous inflorescences.

The most favorable in its genetic effect is xenogamy. Such pollination of flowering plants enhances opportunitiesrecombination of genetic data. This, in turn, ensures an increase in intraspecies diversity, subsequent adaptive evolution. Meanwhile, autogamy has an important significance for the stabilization of species features.

Ways

The method of pollination depends on the agents of grain transferand the structure of the flower. Allogamy and autogamy can be realized with the help of the same factors. They, in particular, are the wind, animals, man, water. The greatest variety of methods differ in the allology. The following groups are distinguished:

Biological - pollination of plants is carried out with the help of living organisms. In this group, several subgroups are distinguished. Classification is carried out depending on the vector. Thus, the pollination of plants by insects (entomophilia), birds (ornithophilia), bats (chiropterophilia). There are other ways - with the help of mollusks, mammals, etc. However, they are rarely found in nature.
Abiotic - pollination of plants is associated with the influence of non-biological factors. In this group, grain transfer is distinguished by wind (anemophilia), water (hydrophilia).

The methods by which pollination of plants, are considered adaptations to specific environmental conditions. In genetic terms, they are less important than types.

Adaptation of plants to pollination

We consider the first group of methods. In nature, as a rule, entomophilia occurs. Evolution of plants and vectors of pollen passed in parallel. Entomophilous individuals are easily distinguished among others. Plants and vectors have reciprocal adaptations. In some cases, they are so narrow that the culture is not able to exist independently without its agent (or vice versa). Insect attracts:

Colour.
Food.
Smell.

In addition, some insects useflowers as a refuge. For example, they hide there at night. The temperature in the flower is higher than that of the external environment by several degrees. There are insects that reproduce themselves in cultures. For example, wasps-chalcids use flowers for this.

Ornithophilia

Pollination is observed mainly in tropical regions. In rare cases, ornithophilia occurs in the subtropics. The signs of flowers that attract birds include:

No odor. Birds have a weak sense of smell.
The corolla is mostly orange or red. In rare cases, a blue or violet color is noted. It is worth saying that birds easily distinguish these colors.
A large amount of slightly concentrated nectar.

Birds often do not sit on a flower, but pollinate, hanging next to it.

Chiropterophilia

Bats pollinate mainly tropicalshrubs and trees. In rare cases, they participate in the transfer of grains to grasses. Bats pollinate flowers at night. The signs of the cultures that attract these animals include:

Presence of fluorescent white or yellow-green color. It can also be brownish, in rare cases purple.
Presence of a specific smell. It resembles the secrets and secretions of mice.
Flowers blossom at night or in the evening.
Large parts hang from branches on long pedicels (baobab) or develop directly on tree trunks (cocoa).

Anemophilia

Pollination of approximately 20% of plants with a moderatestrip is carried out with the help of wind. In open areas (in the steppes, deserts, polar territories), this indicator is much higher. Anemophilic cultures possess the following features:

Small nondescript flowers, having a yellowish or greenish tinge, often not having a perianth. If it is present, it is presented in the form of films and scales.
Presence of multiflorous inflorescences. Such a "bouquet" can be represented by a pivoted axle - an earring.
Presence of anthers on filaments of thin filaments.
Large enough and often pinnate stigmas protruding beyond the flower.
Cultures are single or dioecious.
Formation of a large amount of pollen. It is dry, shallow, smooth. Grains can have additional devices (air bags, for example).

Anemophilic cultures often form large clusters. This significantly increases the chances of pollination. Examples are birch groves, oak forests, bamboo thickets.

Hydrophilia

Such pollination is quite rare innature. This is due to the fact that water is not an ordinary habitat for crops. Many plants have flowers above the surface and are pollinated mainly by insects or by wind. The signs of hydrophilic crops include:

Flowers are small and unattractive. They develop singly or gather in small "bouquets."
As a rule, flowers are same-sex. Examples are vallisneria, elodea.
In the anthers, the wall is thin. In them there is no endotecia. Often anthers are threadlike. In some cultures, they braid the stigma. This contributes to the rapid penetration and germination of pollen.
In the grains there is no exina. This is due to the fact that the pollen is in the water and does not need protection against drying.

Autogamy

75% of plants have bisexual flowers. This ensures independent transfer of grains without external carriers. Autogamy is often accidental. This occurs especially under adverse conditions for carriers.

Autogamy is based on the principle of "betterindependent pollination than none at all. "Such a type of grain transfer is known in many cultures, as a rule, they develop in unfavorable conditions, in areas where there is very cold (tundra, mountains) or very hot (desert) and there are no vectors.

In nature, meanwhile, there is also regular autogamy. It is constant and extremely important for cultures. For example, plants such as peas, peanuts, wheat, flax, cotton, and others are self-pollinated.

Subtypes

Autogamy can be:

Contact When moving the filaments, the anthers directly touch the stigma. Such autogamy is typical for hoofed animal, sickle.
Gravitational. In this case, the pollen enters the stigma from the anthers, located above. When gravitational autogamy, thus, the force of gravity. This is typical of heather, pear species.
Kleistogamnoy. In this case, pollination is carried out in a bud or a closed flower. Cleistogamy is considered an extreme degree of autogamy. It can be caused by adverse factors (high humidity or drought). Cleistogamy can also be regular, genetically fixed. For example, in violet in springtime, normal flowers appear first, but pollination does not occur in them, respectively, fruits and seeds do not appear. Subsequently, the clestogamous reproductive organs appear. They are not disclosed and presented in the form of buds. Germination of pollen occurs directly in the anthers. The tube passes through the wall and reaches the stigma. As a result, a seed box is formed.