Microspore


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Related to Microspore: microgametophyte, microsporocyte, generative cell, Tube cell, microspore mother cell

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 ?
Although this species presented a larger microspore in comparison to 7.
After the tetrads are formed, the inner most of the middle layers begins to degenerate and all of them become flatted during the free microspore stage and have degenerated completely at the mature pollen grain stage.
Evo-devo studies on model plants reveal an increasing number of genes expressed in the tapetum that when silenced (or in natural mutants) cause male-sterility or an arrest of the wild type microspore development (e.
Microspores and pollen grains are produced from microspore mother cells (Microsporocytes), MMCs within loculus anthers (pollen sacs) of the flower.
engelmannii have a reticulate texture formed of regularly anastomosing, lamellate ridges and the microspores have a smooth to papillose surface (Taylor et ah, 1993).
In addition to the method proposed by Guha and Maheshwari for anther excision and inoculation into solid medium, further research has evidenced that microspore embryogenesis can also be achieved through direct microspore isolation from the anther locule and inoculation into liquid medium.
Microspore morphology of Isoetes species (Lycophyta) from Southern South America.
Microspores of the 24 species of Isoetes that grow in southern
Efficient haploid induction in microspore suspension culture of Aesculus hippocastanum and karyotype analysis.
Pfeiffer (1922) was limited to light microscopy for her work but did include some information on diversity of microspore ornamentation.
Produced haploid lines from microspore and anther culture provide high potential for genetic breeding with development of genetic variation through production of completely homozygous lines in short time [3,4,10,9,14,17].