pollination
Plant pollination is the spread of mature pollen grains to the stigma of the pistils of the same flower or other flowers through natural or artificial media, which is only the stage that fertilization must pass through in the process of sexual reproduction of plants.
First, natural pollination
Self-pollination is that pollen falls on the stigma of the same flower, but in practical applications, pollination of different flowers on the same plant, and even pollination between the same crops is called self-pollination. Generally speaking, the conditions for self-pollination are: the position of the stamens and pistils is close, the maturation time is close, and the stigma of the pistils does not inhibit the bearing of pollen particles and the growth of male gametes in the pollen tube.
It is also worth mentioning that similar to peanuts, peas and other plants, they are closed-flower pollination, such plants because the living environment does not allow flowering, resulting in no flowering can complete the pollination function, in fact, it can not be called pollination, that is, the pollen tube directly through the outer wall of the pollen sac, pollen directly falls in the pollen tube. The advantage of closed-flower pollination is that it is safer to complete pollination and is not suitable for the threat of high temperature, high humidity and insects swallowing pollen grains. Closed-flower pollination is similar to auto-pollination, and some people include it in auto-pollination.
Cross-pollination is naturally pollination between different flowers, pollination between different plants in human crop cultivation, pollination between different varieties of fruit trees is also called cross-pollination. The cross-pollination condition is that the position of the stamens pistils is not close; Or the maturity period of stamens pistils is different, such as lettuce and mimosa is the stamens ripening first, plantago and beets are pistils ripening first; Ectopic stamens, well suited to cross-pollination; Pollen cannot fully germinate and develop in the stigma to achieve fertilization, such as buckwheat, grapes, flax, peaches, and pears.
Self-pollination is the result of natural selection in the absence of external pollination methods, and the gamete genes of this pollination are actually similar genes produced in the same environment, which eventually leads to the production of many harmful genes after gene combination, and the survival ability is low, but in the absence of conditions, it is still more valuable than not being refined and the population cannot be sustained; Cross-pollination ensures the effective evolution and optimal combination of genes, so that the population genes are improved in the direction of adapting to the environment, which is more advanced than self-pollination. A typical example is that Prince ginseng has both pollination patterns in both ways, which is a trace of the transition in the process of evolution.
Cross-pollination can only be achieved by relying on external powers, such as wind, water, insects, etc., which can only be achieved under the condition that the structure of the flower uses the corresponding pollination power.
1. Wind-borne flowers About one percent of angiosperms rely on wind pollination, that is, wind-borne flowers, the vast majority of grasses and oaks, framings, poplars, pu trees, birches and other woods belong to this category, and most gymnosperms also belong to this type of pollination method.
Wind-borne flowers are typical hermaphroditic flowers, and their main characteristics are dense pollen, towering stigmas, flowers are discharged, and flowers are limited to long leaves, so that pollen transmission is not blocked.
2. Insect-borne flowers Most angiosperms rely on insects such as bees, butterflies, flies, and moths to spread, which is insect-borne flowers.
Insect flowers are characterized by bright color, can emit a special smell, either fragrant, or smelly, can attract insects to lay eggs, collect honey, convenient to bring pollen out, their pollen itself is more moist and sticky is also a feature, pistils stigma sticky strong, and the flower structure should be consistent with the habits, sizes and other characteristics of the insects that can be attracted.
For example, there are reverse-growing hairs in the aristolochia flower, and the fly enters the flower, is closed in it, struggles to pollinate, the hair falls off, and the fly can escape, and then pollinate other flowers.
3. Waterborne flowers Angiosperms in the water, such as snapdragons, black algae, water turtles, duckweeds, bitter grass, etc., are called waterborne flowers by means of hydraulic pollination. Take typical bitter grass plants as an example, they grow at the bottom of the water, the stamens mature and fall off and float on the surface of the water, the pistils are extended and protrude from the water, the male flowers float towards the female flowers, after fertilization, the female flower stalks curl and shorten to pull the female flowers back to the bottom, and then develop into seeds and fruits.
4. In addition, when hummingbirds and sunbirds ingest nectar, their long beaks can also pollinate, and snails and bats can actually pollinate.
Second, artificial pollination
If natural conditions do not allow, such as unsuitable temperature and humidity, insufficient wind, and few insects, resulting in difficulties in natural pollination, artificial intervention is required, generally it is artificial pollen obtained from stamens to spread to the stigma of the pistil; In addition, when people implement hybrid breeding, often because of the hybridization that needs to be achieved between different plants, either the ripening time is different, or the distance is long, which requires the preservation of pollen, mainly to preserve the conditions of low temperature and low humidity.
#Pollination##Windborne Flower##Insect-borne Flower##Waterborne Flower##Hummingbird Pollination##人工传粉 #
