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Flowering plants may have seen benefits from gametophytic selection occurring during pollen-tube growth in the style. [7] It has been proposed that gametophytic selection contributed to the radiation of flowering plants with closed carpels and more efficient pollen transfer by insects enhancing selective pressure on microgametophytes. [1]
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.
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 ...
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.
The extranuclear genome is only maternally inherited. Natural selection on cytoplasmic genes could also lead to low pollen production or male sterility. Male sterility is easy to detect because a large number of pollen grains are produced in male fertile plants. Pollen grains can be assayed through staining techniques (carmine, lactophenol or ...
Pollination by water, hydrophily, uses water to transport pollen, sometimes as whole anthers; these can travel across the surface of the water to carry dry pollen from one flower to another. [41] In Vallisneria spiralis , an unopened male flower floats to the surface of the water, and, upon reaching the surface, opens up and the fertile anthers ...
The concept, published by Darwin and Alfred Russel Wallace in a joint presentation of papers in 1858, was elaborated in Darwin's influential 1859 book On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. He described natural selection as analogous to artificial selection, a ...
Hydrophilous species fall into two categories: (i) Those that distribute their pollen to the surface of water. e.g. Vallisneria's male flower or pollen grain are released on the surface of water, which are passively carried away by water currents; some of them eventually reach the female flower (ii) Those that distribute it beneath the surface ...