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Home Questions A5TD98X54X
Target Exam

CUET

Subject

Biology

Chapter

Sexual Reproduction in Flowering Plants

Question:

Read the sentence and answer the questions.

After entering one of the synergids, the pollen tube releases two male gametes into the cytoplasm of the synergid. One of the male gametes moves towards the egg cell and fuses with its nucleus, completing syngamy and forming a diploid zygote. Simultaneously, the other male gamete moves towards the two polar nuclei in the central cell and fuses with them, resulting in the formation of a triploid primary endosperm nucleus (PEN). This fusion involving three haploid nuclei is referred to as triple fusion. Endosperm development occurs before embryo development. This sequence is observed because the primary endosperm cell undergoes repeated divisions, giving rise to a triploid endosperm tissue. The cells of this tissue accumulate reserve food materials. In the most common type of endosperm development, the primary endosperm nucleus undergoes successive nuclear divisions, resulting in the formation of free nuclei. This stage of endosperm development is known as free-nuclear endosperm.

Which among the following is a post -fertilization changes in a typical angiosperm ?

Options:

Development of embryo from zygote .

Development of seed from ovule .

Development of endosperm from triploid nucleus .

All of these .

Correct Answer:

All of these .

Explanation:

Following double fertilization in flowering plants, several post-fertilization events occur, which include endosperm and embryo development, as well as the maturation of the ovule into a seed and the ovary into a fruit. These events are collectively referred to as post-fertilization or post-pollination events.

  1. Endosperm Development: After fertilization, the primary endosperm nucleus (PEN) resulting from the fusion of one male gamete with the two polar nuclei undergoes multiple rounds of division. This process forms a triploid endosperm tissue, which serves as a nutritive tissue for the developing embryo. The endosperm cells accumulate reserve food materials such as starch, proteins, and oils.

  2. Embryo Development: Simultaneously, the zygote resulting from the fusion of the other male gamete with the egg cell undergoes further divisions and differentiation, leading to the development of the embryo. The embryo consists of different structures such as the embryonic axis (which includes the shoot apical meristem, cotyledons, and hypocotyl), root apical meristem, and various embryonic tissues.

  3. Maturation of Ovule into Seed: As the endosperm and embryo develop, the ovule undergoes changes and matures into a seed. The seed coat or testa forms from the integuments of the ovule, providing protection to the developing embryo and endosperm. The endosperm and embryo together make up the mature seed, which contains all the necessary structures and nutrients for the future plant.

  4. Maturation of Ovary into Fruit: In parallel with seed development, the ovary surrounding the ovules also undergoes transformation and develops into a fruit. The fruit serves to protect and aid in the dispersal of the seeds. It can have various forms, such as fleshy fruits (e.g., apples, berries) or dry fruits (e.g., nuts, capsules). The fruit may undergo changes in color, texture, and flavor to attract animals for seed dispersal.

Overall, the post-fertilization events, including endosperm and embryo development, maturation of the ovule into a seed, and ovary into a fruit, are crucial processes that ensure the successful reproduction, dispersal, and survival of flowering plants.

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