Tag: reproduction

A pollen grain is the male gametophyte in seed plants. At the time of release, it is considered an immature male gametophyte.

Nucellus, embryo sac, and micropyle are all parts of the ovule. A pollen grain is a separate structure (the male gametophyte) that is not part of the ovule itself.

Asphodelus is known to have a tritegmic ovule, meaning it has three integuments. Most angiosperms are bitegmic or unitegmic.

The pollen is having two layers. The tough outer layer is referred to as the exine. This sophisticated and complex outer layer is having a compound known as sporopollenin. It is waterproof, resistant to the deterioration and very stiff as well. This shell is actually one of nature's most advanced polymers. It ensures that the tender cells must have a strong chance of survival.

Thus the correct answer is option D.

A crassinucellate ovule is characterized by a well-developed nucellus, where the primary parietal cell divides to form a layer of parietal tissue between the epidermis and the megaspore mother cell.

Each microsporocyte (microspore mother cell) undergoes meiosis to produce 4 microspores (pollen grains). Therefore, 4 microsporocytes produce 4 * 4 = 16 pollen grains.

In an amphitropous ovule, the embryo sac is curved into a horseshoe shape, and the micropyle, chalaza, and funicle are brought close together.

The root of a flowering plant is diploid (2n = 24). Gametes are haploid (n), so they contain half the number of chromosomes, which is 12.

In angiosperms, pollen grains are typically shed at either the 2-celled stage (vegetative and generative cell) or the 3-celled stage (vegetative cell and two male gametes).

Endosperm is triploid (3n). Pisum sativum (2n=14, 3n=21), Oryza sativa (2n=24, 3n=36), Nicotiana tabacum (2n=48, 3n=72), Allium cepa (2n=16, 3n=24). Matching: a-v, b-iv, c-i, d-ii.