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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.
The cells of the primary parietal layer divide by successive periclinal and anticlinal divisions to form concentric layers of pollen sac wall. [citation needed] The wall layers from periphery to center consist of: [clarification needed] A single layer of epidermis, which becomes stretched and shrivels off at maturity; A single layer of ...
In the anther, after a microspore undergoes microsporogenesis, it can deviate towards embryogenesis and become star-like microspores. The microspore can then go one of four ways: Become an embryogenic microspore, undergo callogenesis to organogenesis (haploid/double haploid plant), become a pollen-like structure or die. [6]
Microgametogenesis is the process in plant reproduction where a microgametophyte develops in a pollen grain to the three-celled stage of its development. In flowering plants it occurs with a microspore mother cell inside the anther of the plant.
In megasporogenesis, often three of the four spores degenerate after meiosis, whereas in microsporogenesis all four microspores survive. In gymnosperms, such as conifers, microspores are produced through meiosis from microsporocytes in microstrobili or male cones. In flowering plants, microspores are produced in the anthers of flowers.
Microsporogenesis (part of pollen formation) distinguishes some members of Asparagales from Liliales. Microsporogenesis involves a cell dividing twice (meiotically) to form four daughter cells. There are two kinds of microsporogenesis: successive and simultaneous (although intermediates exist).
Earlier pollen researchers include Früh (1885), [16] who enumerated many common tree pollen types, and a considerable number of spores and herb pollen grains. There is a study of pollen samples taken from sediments of Swedish lakes by Trybom (1888); [ 17 ] pine and spruce pollen was found in such profusion that he considered them to be ...
Microsporogenesis of H. punctatum is abnormal in many ways. Rather than pair at diakinesis the chromosomes link together in a chain and during the first metaphase the chromosomes tend to separate and alternate members move to opposite poles. Irregularities often occur such that at second metaphase the haploid number is seven or nine rather than ...