The final task of a typical flower is the formation of fruits and seeds. Two processes are necessary for this. The first is the pollination of plant flowers . After it, fertilization itself occurs - fruits and seeds appear. Let us further consider what types of pollination of plants exist.
General information
Pollination of plants is the stage at which the transfer of small grains from stamens to stigmas is carried out. It is closely related to another stage of crop development - the formation of the reproductive organ. Scientists have established two types of pollination: allogamy and autogamy. In this case, the first can be implemented in two ways: geytonogamy and xenogamy.
Characteristics
Autogamy is the pollination of plants by transferring grains from stamens to the stigma of one reproductive organ. In other words, one system independently carries out the necessary process. Allogamy is the cross-transfer of grains from the stamens of one organ on the stigma of another. Geitogamy involves 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 in one individual takes place. As a rule, such pollination is characteristic of multi-flowered inflorescences.
The most favorable in its genetic effect is xenogamy. This pollination of flowering plants increases the potential for recombination of genetic data. This, in turn, provides an increase in intraspecific diversity, subsequent adaptive evolution. Meanwhile, autogamy is of no small importance for the stabilization of species characteristics.
Ways
The pollination method depends on the grain transfer agents and flower structure. Allogamy and autogamy can be carried out using the same factors. They, in particular, are the wind, animals, people, water. The greatest variety of different methods for allogamy. The following groups are distinguished:
- Biological - pollination of plants is carried out using living organisms. In this group, several subgroups are distinguished. Classification is carried out depending on the carrier. So, pollination of plants by insects (entomophilia), birds (ornithophilia), and bats (chiropterophilia) is carried out. There are other methods - using shellfish, mammals, etc. However, they are detected in nature quite rarely.
- Abiotic - pollination of plants is associated with the influence of non-biological factors. In this group, the transfer of grains with the help of wind (anemophilia), water (hydrophilia) is distinguished.
The methods by which pollination of plants is carried out are considered adaptations to specific environmental conditions. Genetically, they are less important than types.
Pollination of plants
Consider the first group of methods. Entomophilia is usually found in nature. The evolution of plants and pollen carriers took place in parallel. Entomophilous individuals stand out among others easily. Plants and carriers have mutual adaptations. In some cases, they are so narrow that the culture is not able to exist independently without its agent (or vice versa). Attracts insects:
- Color.
- Food.
- Smell.
In addition, some insects use flowers as a refuge. For example, they hide there at night. The temperature in the flower is several degrees higher than in the environment. There are insects that reproduce themselves in crops. For example, chalcid wasps use flowers for this.
Ornithophilia
Pollination by birds is observed mainly in tropical areas. In rare cases, ornithophilia occurs in the subtropics. The signs of flowers that attract birds include:
- Lack of smell. Birds have a rather weak sense of smell.
- The whisk is mostly orange or red. In rare cases, a blue or purple color is noted. It is worth saying that birds easily distinguish these colors.
- A large amount of weakly concentrated nectar.
Birds often do not sit on a flower, but pollinate, hovering next to it.
Chiropterophilia
Bats pollinate mainly tropical shrubs and trees. In rare cases, they are involved in the transfer of grains to herbs. Bats pollinate flowers at night. The signs of cultures that attract these animals include:
- The presence of fluorescent white or yellow-green color. It can also be brownish, in rare cases purple.
- The presence of a specific smell. It resembles the secrets and secretions of mice.
- Flowers bloom 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 temperate plants is carried out using wind. In open areas (in the steppes, deserts, polar territories), this figure is much higher. Anemophilic cultures have the following characteristics:
- Small nondescript flowers with a yellowish or greenish tint, often without a perianth. If it is present, then it is presented in the form of films and scales.
- The presence of multi-flowered inflorescences. Such a "bouquet" can be represented by a dangling axis - an earring.
- The presence of anthers on stamen thin filaments.
- Large enough and often cirrus stigmas protruding beyond the flower.
- Monoecious or dioecious cultures.
- The formation of large amounts of pollen. It is dry, shallow, smooth. Grains may have additional devices (air bags, for example).
Anemophilic cultures often form large clusters. This greatly increases the chance of pollination. Examples are birch groves, oak forests, bamboo thickets.
Hydrophilia
Such pollination is quite rare in nature. This is due to the fact that water is not the usual habitat for crops. In many plants, flowers are above the surface and are pollinated mainly by insects or with the help of wind. The signs of hydrophilic cultures include:
- The flowers are small and nondescript. They develop singly or gather in small "bouquets".
- As a rule, flowers are same-sex. As examples are Wallisneria, Elodea.
- In anthers, the wall is thin. They lack endothecia. Often anthers are filiform. In some cultures, they braid the stigma. This contributes to the rapid penetration and germination of pollen.
- There are no exins in the grains. This is due to the fact that pollen is in the water and does not require protection from drying out.
Autogamy
In 75% of plants, bisexual flowers are present. This provides an independent transfer of grains without external carriers. Autogamy is often random. This is especially the case under adverse conditions for carriers.
Autogamy is based on the principle "self-pollination is better than none at all." This type of grain transfer is known in many cultures. As a rule, they develop in adverse conditions, in areas where it is very cold (tundra, mountains) or very hot (desert) and there are no carriers.
In nature, meanwhile, there is regular autogamy. It is constant and extremely important for cultures. For example, plants such as peas, peanuts, wheat, flax, cotton, and others self-pollinate.
Subtypes
Autogamy can be:
- Contact. When the stamens move, the anthers directly touch the stigma. Such autogamy is characteristic of the ungulates, the henchmen.
- Gravity. In this case, pollen enters the stigma from anthers located higher. With gravitational autogamy, gravity therefore acts. This is characteristic of heather, pear-tree crops.
- Kleistogamnoy. In this case, pollination is carried out in a bud or a closed flower. Kleistogamy is considered an extreme degree of autogamy. It can be caused by adverse factors (high humidity or drought). Kleistogamy can be regular, genetically fixed. For example, in the amazing violet in spring, first normal flowers appear, but pollination does not occur in them, respectively, fruits and seeds do not appear. Subsequently, cleistogamous reproductive organs appear. They do not open and are 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 box with seeds is formed.
Kleistogamy is found in various systematic groups of cultures (in some cereals, for example).