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 ?
Moreover, 10 days after flower budding, tetrads began to form microspores, the tapetal cells were ruptured, and their cytoplasm dispersed in the pollen chamber (Fig.
Hence, the aim of this study was to determine the best microspore development stage of the flower buds in KB6 variety of kenaf and cultured on MS medium with different concentrations of hormones for the induction of callus.
Abnormal microspores give rise pollen grains with different sizes and amount of genetic material, pollen grains 2n and unbalanced (Figure 2G).
Cytological analysis of buds of different length revelaed higher percentage greater than 80% of uni-nucleate to early bi-nucleate microspores in medium sized (13-15 mm) buds compared with other categories.
Stage 4: microspores vacuole with a developed exine wall:
Many new developments and data can be expected if functional genetic experiments on model plants, set up to identify the genes and gene products that control sporopollenin polymerisation and patterning, take both microspores and orbicules into account when screening phenotypes.
These irregularities, which also contributed towards the formation of monads, dyads and triads, resulted in normal imbalanced 2n and 4n microspores. According to the observed MI of 71.83% in P.
microspore: Haploid cells produced by meiosis in the anthers of angiosperms; four microspores are produced from a single microsporocyte.
Keywords: Petunia hybrida; Microspores; In vitro culture; Agrobacterium-mediated; Transformation
In spite of great diversity, especially in the complexity of the sporoderm, the fundamental components of sporogenesis are the same in free-sporing plants, where the walled spores serve to disperse new plants, and in seed plants where the walled microspores have evolved into pollen grains for transmission of male gametes.
The growth of this market is driven mainly by factors such as increasing demand for high-end microscopy systems in various applications and technological advancement in microspores. Increasing demand from an emerging market in developing countries is expected to create significant growth opportunities for players in the ion milling system market during the forecast period.
Keratinase of Doratomyces microspores. Appl Microbiol Biotechnol 2000;53:196-200.