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 ?
Effects of cold pretreatment on the induction of microspore embryogenesis in anther culture of pepper
Each of the four haploid microspores enlarges and develops into a pollen grain, as shown in Figure 12-4.
Then the wall surrounding the each microspore cells dissolve and the microspores in the pollen sac are released.
Using one of the search engines on the Internet, such as Google, Yahoo!, Ask.com, or MSN Live Search, find more information by searching for these words or phrases: after riping, dioecious, generative cell, integument, microsporangia, microspore mother cell, nucellus, ovule, polyembryony, seed coat, self-incompatible, and tube cell.
Key words: Microspore culture, callus, colchicine, Raphanussativus L.
Exuberant metabolism of the tapetum could provide enzymes, hormones, favorable nutrition for developing PMCs and microspores, and regulate the proper release of microspore (Zhao et al., 2002; Jung et al., 2005; Vinod, 2005).
There was a significant correlation between microspore mother cell divisions and anther's tapetum development that is coincides with other reports for dicotyledonous plants [7,10,6].
This resemblance in ornamentation indicates that a similar patterned biosynthesis of sporopollenin is possible on an a-cellular sporophytic structure (pro-orbicule) as on a cellular gametophytic structure (microspore).
One of the most popular methods for production of haploids is through anther and microspore culture on the artificial culture medium.
generative nucleus: Produced by the haploid microspore nucleus of a pollen grain, the generative nucleus divides mitotically to form two sperm nuclei.