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SubjectsBiology
पुष्पीय पौधों में लैंगिक प्रजनन
In this Class 12 Biology topic, students learn how flowering plants reproduce sexually through the formation of male and female gametophytes, pollination, pollen–pistil interactions, fertilisation, and the development of seeds and fruits. It explains double fertilisation, embryo and endosperm formation, and the role of meiosis in generating variation. In connection with the parent context, Molecular Basis of Inheritance, the topic links reproductive events with genetic continuity and inheritance in plants.
TOPIC PRACTICE
Up to 9 questions from this page. Select your focus, then start.
When a pollen grain germinates on the stigma, it produces a pollen tube. The tube grows through the style and enters the ovule, eventually reaching the embryo sac and delivering the two male gametes. The embryo sac, integument, and style are separate structures and do not themselves transport the gametes.
Pollination is the transfer of pollen grains from the anther to the stigma. It may occur within the same flower or between flowers of the same or different plants. Therefore, option A is correct. Option B describes fertilisation, option C describes pollen germination and pollen-tube formation, and option D describes seed development from an ovules after fertilisation.
In flowering plants, the female gametophyte is called the embryo sac. It develops within the ovule and contains the egg cell and other cells involved in reproduction. A pollen grain is the male gametophyte, the pollen tube transports the male gametes, and the ovule is the structure that contains the embryo sac.
A typical mature angiosperm embryo sac is seven-celled and eight-nucleate. It contains three cells forming the egg apparatus, three antipodal cells, and one central cell. The central cell contains two polar nuclei, so there are eight nuclei but only seven cells. This distinction makes seven the unambiguous answer.
The governing concept is the organisation of a typical angiosperm embryo sac. It is seven-celled but eight-nucleate: three antipodal cells contribute three nuclei, two synergids contribute two, and the egg contributes one. The central cell contains two polar nuclei. Thus the total is 3 + 2 + 1 + 2 = 8, making option B correct. Seven refers to cells, not nuclei.
In a typical mature angiosperm embryo sac, three antipodal cells occur at the chalazal end, which is opposite the micropyle. The micropylar end contains the egg apparatus—one egg cell and two synergids. The stigma and pollen tube are not ends or cellular groups of the embryo sac, so they cannot be correct.
Endosperm is a nutritive tissue that generally develops after triple fusion during double fertilisation in angiosperms. Its main function is to nourish the developing embryo by supplying stored materials such as starch, proteins, and oils. The seed coat develops from the integuments, not from the endosperm.
In the traditional school-level classification of angiosperms, embryos with one cotyledon are called monocots, whereas embryos with two cotyledons are called dicots. Roots and stems are plant organs, algae and fungi are different biological groups, and male and female refer to sex rather than cotyledon number.
The single cotyledon of a monocot embryo is called the scutellum, especially in the standard description of a grass embryo. It helps absorb nutrients from the endosperm. The coleoptile protects the plumule, the coleorhiza protects the radicle, and the epiblast is an additional structure rather than the cotyledon.
QUIZ COMPLETE
