What is the crossed pollination? Concept and definition
The crossed pollination is, without doubts, the met type of pollination more. External pollenizer is the transference of the pollen of a plant towards another one through an agent (main difference with the direct pollination).
The crossed pollination consists of the transference of the pollen of a plant towards another one through an agent external pollenizer.
Alogamia, Xenogamia and Geitonogamia
Autogamia is a process sexual reproduction - singamia (union of sperm cells) - in which the sperm cells come from the same individual.
When speaking of plants, alogamia is synonymous of crossed pollination, but the pollination crossed in the plants can also be produced between flowers different from a same individual - it also plants, and between flowers of different individuals but that they are genetic clones. This way, two types of alogamia appear: xenogamia and geitonogamia. In xenogamia, flowers of individuals different genetically, whereas in geitonogamia equals take part genetically individual or, which from genetic level take part gives the same result, flowers different from a same individual.
That is to say, since the plants can reproduce asexually and give rise to individuals genetically cloned (stocks), two types are different themselves from alogamia:
Xenogamia: it is the crossed pollination that occurs between individuals - you plant different
Geitonogamia: it is the crossed pollination that occurs between different flowers but of the same individual - it plants or between flowers of different individuals but genetically equals (it enters clones or stocks)
Types of crossed pollination
Pollination entom³fila (insects)
Pollination ornit³fila (birds)
Pollination zo³fila (animal)
Anemophilous pollination (wind)
The anemophilous pollination is a type of abiotic crossed pollination that is carried out by driving of the wind (air in movement).
Pollination hydrophilia (water)
The pollination hydrophilia is a class of abiotic crossed pollination that is carried out by driving of the water.
Importance of the crossed pollination
The crossed pollination becomes necessary when sexes masculine and feminine are not in the same plant, as for example in the case of the melon, although also it can occur when both sexes appear in different periods from the blossoming of a same plant, as it happens in the case of the avocado.
The main advantage of the crossed pollination is in which it makes possible to assure the variability the species and the survival to the changes of environment.
When the crossed pollination is obligatory
In many species, the crossed pollination is obligatory, since they do not have possibility of realising the process of direct form. This is due to the self-incompatibility of certain flowers, that is to say, the existence of certain genetic and physiological barriers that they by themselves do not allow the germination of pollen and the development of the call polnico tube that takes to the masculine sperm cell until the ovum for its fertilization, qualifying the direct pollination.
The self-incompatibility of these species can be of two types. On the one hand, we have the esporoftica incompatibility, that depends exclusively on the wall of the pollen grain. In these cases, the grain cannot germinate due to the lack of compatibility between present proteins of recognition in esporodermis, and the receivers located in the stigma.
On the other side, we have the gametoftica incompatibility, which depends on the genetic constitution of the masculine gametophyte. Here, pollen can obtain the germination, but the growth of its polnico tube pauses after the penetration in the style.
Crossed pollination and agriculture
The species of plants are many whose reproduction depends on the crossed pollination, and agriculture is not an exception. For that reason it is extremely important to protect the biodiversity in the land: so that diverse populations of insects realise the pollen interchange that power the growth of the cultures that they feed the world. In order to know more on pollination and agriculture, we invited to you to know our project Multifunctional Landscapes.