Wednesday, January 7, 2009

Ways of Reproduction in Plants

rIn higher plants there are mainly two methods of reproduction-sexual reproduction that involves the formation of gametes and asexual or vegetative reproduction, in which there the vegetative parts are used for propagation.

Sexual Reproduction
Typically, plant life history involves alternation of generations, during which a diploid sporophyte gives rise to a haploid gametophyte. The gametophyte generation produces gametes that, through syngamy (fusion of gametes during fertilization), provide for another generation of diploid sporophytes, to continue the cycle. The sporophyte does not produce gametes but rather, meiosis occurs in spore mother cells and produces haploid spores. These spores divide mitotically to form gametophytes, which subsequently produce gametes via mitosis. Within the plant kingdom the dominance of phases varies. In nonvascular plants such as mosses and liverworts, the gametophyte phase is dominant. Vascular plants show a progression of increasing sporophyte dominance from the ferns and "fern allies" to angiosperms.

In angiosperms, flowers are the organs of reproduction. A typical flower has four parts arranged in circles: sepals, petals, androecium, and gynoecium from periphery to center. Androecium and gynoecium are the male and female reproductive organs.

The male reproductive organ of the flower is composed of units called stamens. Each stamen consists of a filament and an anther. The anther produces the male spores called pollen grains.

The female reproductive organ consists of units called pistils. Each pistil consists of terminal filament called style with stigma at its terminal part and an ovary, from which the style starts. The ovary contains ovules. The flowers may be bisexual with both male and female organs in the same flower, or it may be unisexual with anyone type of sex organs. The male flowers are the staminate flowers and the female flowers are the pistillate flowers.

Tags: Bio Genetics, Bio Technology, Reproduction

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