Microspore


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microspore

[′mī·krə‚spȯr]
(botany)
The smaller spore of heterosporous plants; gives rise to the male gametophyte.

Microspore

 

a small spore of heterosporous Pteridophyta (Selaginella, Isoetes, Salvinia, and other water ferns) and seed plants. Microspores are usually formed in large numbers in special organs, the microsporangia, as a result of meiosis of arche-spores. Consequently, microspores are haploid. The microspore is covered with a thin inner membrane (inline) and a thicker outer membrane (exine). When the microspore of a pteridophyte sprouts (usually in the microsporangium), it forms a greatly reduced male prothallium with sex organs, the antheridia. The sprouted microspores (prothallia) are transported by water, wind, or other agents, to the female prothallia, where the spermatozoids, freed from the antheridia, penetrate the archegonia for fertilization.

In seed plants the pollen grain, which is homologous to the male prothallium, arises from the microspore in the microsporangium. In gymnosperms the pollen grain consists of several vegetative cells and one antheridial cell and forms the male gametes (in sago palms and ginkgoes there are flagellate spermatozoids; the rest of the gymnosperms have nonmotile spermatozoids). Angiosperms have the most reduced male prothallia, consisting of one vegetative and one generative cell. After the pollen falls on the stigma of the pistil, the vegetative cell becomes extended into the pollen tube and the generative cell divides, forming two spermatozoids, of which one merges with the egg cell and the other merges with the secondary nucleus of the embryo sac.

WORKS

Komarnitskii, N. A., L. V. Kudriashov, and A. A. Uranov. Sistematika rastenii. Moscow, 1962.

L. V. KUDRIASHOV

References in periodicals archive ?
In species belonging to the Brassicaceae family, the microspore culture, which is one of the haploidy techniques can also be utilized to shorten the duration of plant breeding studies.
Then the wall surrounding the each microspore cells dissolve and the microspores in the pollen sac are released.
The question as to whether the wall around the haploid microspore, and especially its ornamentation or patterning, is controlled by the microspore itself or by the diploid, sporophytic tapetum has long challenged angiosperm palynologists (reviewed by Blackmore et al.
microspore mother cell: Diploid mother cell that will go through meiosis to produce the (4) haploid microspores.
Alternate techniques involve development of haploids using anther culture microspore culture and ovule culture.
This paper offers a partial remedy to this situation by providing an account of anther wall, tapetum, microspore, male gametophyte development and pollen morphology in S.
The meiotic division in the MMC is synchronic with the microspore mother cells.
Fertile indica rice plants regenerated from protoplasts isolated from microspore cell suspensions.