Pollen

The pollination, transferred to the stigma on pollen and stigma in the interaction, the long process of pollen tube germination hole.
Pollen

Pollen pollen grain germination

(pollen grain germination)
The mature pollen to the stigma, through mutual recognition, rejection of distant and dissimilar pollen grains of different genus, treated with pollen, or reject their (monoecious or with flowers) pollen grains treated with different genotypes of pollen grains. Is stigma accepting have an affinity for the pollen, water swelling, wall by the aperture on the exterior wall of the protrusion, the formation of pollen tube, to germination. From the pollen to the stigma to germination, required after a certain period of time. The time varied with species. Such as rice, sugarcane, sorghum, germination almost immediately after pollination; corn, rubber grass takes about 5 minutes; cotton needs 1 ~ 4 hours.

Pollen The main factors of germination

The pollen grain storage of enzymes and metabolites, is an important factor in pollen germination. For example, the pollen grains and the Pollen tube In the presence of cutinase, can exist in most plant cuticle degradation stigma surface, the pollen germination can absorb the necessary moisture from the stigma tissue, and open a channel for the growth of pollen tube. Metabolism of pollen grains in storage. Provides the material basis for the initial growth of pollen tube. In addition, the wet stigma surface secretions, provide the necessary substrate for pollen germination, especially the changes of the phenolic compounds, the pollen germination can promote or inhibit. No stigma dry discharge, but the hydrophilic protein film on the surface, auxiliary adhesive or hydrated pollen pollen, pollen germination of the essential role of water. In the stigma and style of organization, widespread boron, increased oxygen absorption and promote the absorption and metabolism of sugar, pectin to synthesis, and the pollen germination and Pollen tube The growth promoting effect.
 Pollen Pollen
Pollen grains in artificial culture medium or germinated on the stigma, in certain area, the number of pollen grains, the germination rate is high, the growth of pollen tube or, for example, apple pollen per milliliter of medium containing 40 x 103 seeds, the germination rate was 13%, with 280 x 103 seeds, germination the rate soared to 74%. This phenomenon is called pollen Collective effect And, a pollen grain itself on the secretion of pollen germination and effective pollen growth factor related substances.

Pollen Form

All kinds of plant pollen is different. According to the shape of pollen size, symmetry and polarity, Germination hole The number, position and structure, wall structure and surface carved, often can be identified to genera and families, and even can be identified to species. Study on the pollen morphology for classification and identification Pollen analysis In the identification of Fossil Provide the basis for the pollen, but also for the plant System development The study provides valuable information.
Most of the mature pollen is dispersed, a single pollen. But there are two more pollen bonded together, called compound pollengrain. Many pollen together in a The chamber At least more than two blocks, called massula. All pollen in one or several chambers grain bonded together, called Pollinium . Pollen and pollen mainly in small pieces Orchid and Asclepiadaceae Botany。
Pollen grains in Four split And in part, called the adaxial. The outward part is called the distal side. Connect the center point and the adaxial pollen center of the distal side of an imaginary line called the polar axis, polar axis and a line perpendicular to the called equatorial axis, along the surface of the line between the poles for the pollen. In polar pollen, can be divided into 3 types such as, subisopolar and hemimorphic. Pollen is usually symmetrical, there are two kinds of symmetry and symmetry about radiation: Symmetric .
Pollen is spherical, Equatorial axis Longer than Polar axis Called super oblate spheroid; especially for flat; on the contrary, the polar axis is longer than the equatorial axis is called prolate, especially long called perprolate. Pollen in polar view see equatorial contour, can be circular, angular shape, with lobelike etc.. In equatorial view, pollen profile can be circular, oval, diamond, square and so on.
Pollen size for different species, great changes. The smallest in pollen Boraginaceae Forget me not, about (4 ~ 8) * (2 ~ 4 micron micron). The large pollen diameter of 100 to 200 microns, ginger is, from 120 to 150 microns, Malvaceae Many species of Petunia and Musa, etc.. The maximum diameter of most pollen was about 20 to 50 microns. Aquatic plant z.marina pollen slender, about (1200 ~ 2900) * (3.5 ~ 9.5 micron micron).
Germination hole The thinning area for the pollen wall, pollen germination when pollen tube germination often by the hole. The aperture according to the length and width ratio is usually divided into two types of ditch, hole. Where the length and width ratio is greater than 2 for the ditch, less than 2 of the hole. Sometimes between the short channel and long hole is not easy to distinguish. With only the groove or hole is a simple germination hole, groove and holes form the composite aperture. The aperture distribution in polar and equatorial or spread on the surface. The single channel distribution in the far side, also known as the trough. There is a lot of variation in germination, no pollen germination hole.
The pollen wall is usually divided into two layers, namely the inner and outer walls. The inner wall is mainly composed of pectin cellulose, poor resistance, easy to rot in the ground, after alkali treatment is decomposed; while the main component is the outer wall Pollen Pigment, anti corrosion and anti acid ability, in the formation of the millions of years is still intact, so the study on the pollen morphology and structure of the outer wall of the main basis. The outer layer is generally composed of 3 layers, the outer covering layer, or with the perforation, incomplete development, with half cover or intectate pollen. Below A layer of columnar layer with columnar structure (or rod). At the next level for the grassroots.
Pollen surface smooth or with a variety of ornamentation (glyph). The type of ornamentation for different species. The main glyph is granular, nodular, clavate, spiny, striped, crisped, mesh cerebelloid, etc..

Pollen type

The mature pollen grain Yes, only Vegetative cells and germ cell So, the pollen grains, called Two nucleus pollen grain . There are about 192 families of angiosperm plants is such, such as cotton, peach, plum, tea, orange Yang, etc.. Some other plant pollen before maturity , A germ cell Mitosis Two, the formation of sperm (no sperm in angiosperms Flagellum ) So, when there is a mature pollen in the vegetative nucleus and two Sperm cells And this kind of pollen grains, called Three nucleus pollen grain , about 115 families, such as rice, barley, wheat, maize, rape pollen. Two nuclear pollen Sperm cells (angiosperm sperm atrichous) was formed in the pollen tube .