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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 competitive ability of pollen grains (microgapmetophytes) is rooted in the expression of their haploid genomes. The haploid genes are expressed immediately after pollen development and during pollen germination and pollen-tube growth. [2] About 60% of genes expressed in the sporophyte are also expressed in the microgametophyte. [3]
The pollen grains were small, between 25 and 30 μm in diameter. The size of the pollen grains supports the idea that they were wind-pollinated, and their bisaccate wings may have enabled entry into the seed by a pollination drop mechanism. [1] In both respects they were like pollen of pine trees. [4]
[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]
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 ...
SEM image of pollen grains. Sporopollenin is a biological polymer found as a major component of the tough outer (exine) walls of plant spores and pollen grains. It is chemically very stable (one of the most inert among biopolymers) [1] and is usually well preserved in soils and sediments.
They freely expel a myriad of these pollen grains, and only a small percentage of them ends up captured by the female floral structures on wind-pollinated plants. [3] They are typically 20–60 micrometres (0.0008–0.0024 in) in diameter, although the pollen grains of Pinus species can be much larger and much less dense. [ 1 ]
Bioaerosols can range in size from 10 nanometer virus particles to 100 micrometers pollen grains. [6] Pollen grains are the largest bioaerosols and are less likely to remain suspended in the air over a long period of time due to their weight. [1] Consequently, pollen particle concentration decreases more rapidly with height than smaller ...