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Pollen itself is not the male gamete. [4] It is a gametophyte, something that could be considered an entire organism, which then produces the male gamete.Each pollen grain contains vegetative (non-reproductive) cells (only a single cell in most flowering plants but several in other seed plants) and a generative (reproductive) cell.
Stigmas can vary from long and slender to globe-shaped to feathery. The stigma is the receptive tip of the carpel(s), which receives pollen at pollination and on which the pollen grain germinates. The stigma is adapted to catch and trap pollen, either by combining pollen of visiting insects or by various hairs, flaps, or sculpturings. [27]
The male reproductive organ of the flower, the stamen, produces pollen. The opening of anthers makes pollen available for subsequent pollination (transfer of pollen grains to the pistil, the female reproductive organ). Each pollen grain contains a vegetative cell, and a generative cell that divides to form two sperm cells.
The male gametophyte is produced inside a pollen grain within the anther and is non-motile, but can be distributed by wind, water or animal vectors. When a pollen grain lands on a mature stigma of a flower it germinates to form a pollen tube that grows down the style into the ovary of the flower and then into the ovule. The pollen then produces ...
The anther produces pollen grains that contain male gametophytes. The pollen grains attach to the stigma on top of a carpel, in which the female gametophytes (inside ovules) are located. Plants may either self-pollinate or cross-pollinate. The transfer of pollen (the male gametophytes) to the female stigmas occurs is called pollination.
Pollen of angiosperms must be transported to the stigma, the receptive surface of the carpel, of a compatible flower, for successful pollination to occur. After arriving, the pollen grain (an immature microgametophyte) typically completes its development. It may grow a pollen tube and undergo mitosis to produce two sperm nuclei.
[10] (also called pollen vectors): organisms that carry or move the pollen grains from the anther of one flower to the receptive part of the carpel or pistil (stigma) of another. [11] Between 100,000 and 200,000 species of animal act as pollinators of the world's 250,000 species of flowering plant. [ 12 ]
Each of the microsporocytes in the microsporangia undergoes meiosis, producing four haploid microspores. These develop into pollen grains, each consisting of four cells and, in conifers, a pair of external air sacs. The air sacs give the pollen grains added buoyancy that helps with wind dispersal. [3] Types of Gymnosperms: Conifers. Pines ...