What is pollination? How many types are there?

Pollination is a necessary process for plants to form fruits. Flowers usually have some yellow powder called pollen. This pollen needs to be passed on to some flowers of similar plants. The movement of pollen from anther to stigma is called pollination. ?

1. According to different pollinators, plants can be divided into self-pollination and cross-pollination. ?

1, self-pollination, the process in which mature pollen grains of plants are transferred to the stigma of the same flower and can be fertilized normally is called self-pollination. In production, pollination between different flowers of the same plant and between different plants of the same variety is often considered as self-pollination. Plants that can self-pollinate are called self-pollinating plants, such as rice, wheat, cotton and peaches. Peas and peanuts don't bloom, buds mature, pollen grains germinate directly in pollen sacs to form pollen tubes, and sperm are sent to embryo sacs for fertilization. This pollination method is a typical self-pollination, called closed pollination. ?

2. Cross-pollination: Under normal circumstances, even bisexual flowers, the pistil and pistil of the same flower will not mature together. So the pollen received by the pistil of an ordinary flower is the pollen of another flower, that is, cross pollination. Of course, for dioecious plants, cross-pollination is the only way if monoecious plants have monoecious flowers. Rapeseed, sunflower and apple are cross-pollinated plants. ?

Second, according to the different ways of plant pollination, it can be divided into natural pollination and artificial assisted pollination.

1. Natural pollination can be divided into wind vector, insect vector, water vector and bird vector. ?

2. Artificial pollination is also called human pollination. In agricultural production, artificial pollination is often used to overcome the defect that pollination cannot be guaranteed because of insufficient conditions, so as to achieve the expected yield. In the rejuvenation of varieties, artificial pollination is also needed to achieve the expected goal. Artificial pollination can greatly increase pollen grains on the stigma, increase the relative total amount of hormones contained in pollen grains, correspondingly strengthen enzyme reaction, promote pollen germination and pollen tube growth, and greatly improve fertilization rate. Pollen grains germinate on the stigma after pollination. With the elongation of pollen tube, vegetative nucleus and sperm nucleus enter embryo sac. Then the sperm nucleus is fertilized with the egg cell to form a fertilized egg, which will develop into an embryo (2n). After fertilization, another sperm nucleus will combine with two polar nuclei to form endosperm nucleus (3n), which will develop into endosperm (3n). Therefore, this process is called double fertilization. Through subsequent double fertilization, it finally develops into seeds.