Botany and Plant Science

The typical mature embryo sac (Polygonum type) consists of an egg apparatus (2 synergids + 1 egg cell), 3 antipodal cells, and 2 polar nuclei in the central cell.

The primary endosperm nucleus is formed by the fusion of two polar nuclei and one male gamete, resulting in a triploid (3n) state, which is unique to angiosperms.

Each meiotic division of a megaspore mother cell produces 4 megaspores. To produce 100 functional megaspores (assuming one per division), you need 100 meiotic divisions.

Spermatophytes (seed plants, including gymnosperms and angiosperms) do not require external water for fertilization because they use pollen tubes to deliver sperm to the egg.

I, III, and IV are correct. II is incorrect because not all angiosperms have monosporic embryo sacs; some are bisporic or tetrasporic.

Megaspores are haploid (n), produced by meiosis from the diploid megaspore mother cell. The option stating they are diploid is false.

Anona squamosa (custard apple) belongs to the Annonaceae family, which features superior ovaries, monocarpellary conditions, and marginal placentation.

During microsporogenesis, the microspore mother cells are surrounded by a callose wall, which is later degraded by the enzyme callase to release the microspores.

In angiosperms, the egg cell within the embryo sac is a distinct cell enclosed by a plasma membrane and a cell wall, unlike some primitive plants where gametes might be naked.

Gnetum is considered to have affinities with angiosperms because it possesses xylem vessels and lacks archegonia, which are absent in angiosperms but present in other gymnosperms.

The process in which both nuclei from the pollen tube fuse is referred to as double fertilization. This is perhaps the most characteristic single feature of angiosperms and is not shared with any other group. Gymnosperms, in sharp contrast, have a multicellular female gametophyte, that consists of many hundreds or even thousands of cells. Double fertilization does not take place in this case, and the female gametophyte develops into the food-storage tissue of the seed.

Angiosperms or flowering plants are those plants in which seeds are formed inside fruits and the sporophylls are organised into flowers. They are the most recently and highly evolved plants appeared on Earth about 130 million years ago. The plant body is differentiated into root, stem and leaves. At maturity the plants bear flowers, which produces fruits and seeds. The vascular tissues are arranged in the form of vascular bundles. Xylem contains vessels and phloem has sieve tubes and companion cells. 

An angiospermic dicot seeds has a protective seed around it. It is made up of 2 cotyledons. The outer seed coat is called testa and inner seed coat is called tegmen. It's embryonic axis has 3 parts, plumule, radicle and hypocotyl.

Drimys is a primitive angiosperm belonging to the Winteraceae family, which is notable for lacking vessels in its xylem, a trait usually associated with gymnosperms.

Dichogamy (maturing at different times) in the prothallus of vascular cryptogams prevents self-fertilization, thereby promoting cross-fertilization and genetic diversity.