Test: Sexual Reproduction in Flowering Plants - 1 - NEET MCQ

Assertion (A) is true because apomixis is an asexual process that results in seed formation without fertilization.

Reason (R) is false because apomictic plants do produce seeds despite the lack of fertilization.                                                                                      So option (A) is True but (R) is False is correct .

(A) To determine the correctness of the statements regarding the given diagram:

- Statement I: The pollen tube enters a synergid under guidance from A, which is correct.
- Statement II: Male gametes are discharged into a synergid, which is correct

Statement I is correct, Statement II is correct SO OPTION (A)
 

PEN (primary endosperm nucleus) divides into two nuclei and subsequent division of nucleus produce large number of nucleus without cell wall formation. These types of endosperm are called free nuclear type of endosperm.

Double fertilisation involves fusion of one male gamete with egg during Syngamy and fusion of two polar nuclei with other male gametes. So, total 5 nuclei are involved in double fertilisation.

The flower in which pollen grain is transferred from anther to stigma of anther flower by insects are colorful to attract insects and contain nectar.

The correct option is A Epicotyl
Plumule- Shoot tip.

Radicle - Embryonic root.

A. Epicotyl- The portion of axis between the plumule and the cotyledonary node.

B. Hypocotyl- The portion of axis between the radicle and the cotyledonary node.

D. Coleoptile- Protective sheath of plumule.

So, the correct answer is 'Epicotyl'

Anther is bilobed structure at the tips of stamen. Each lobe consists of two theca. Each theca change into microsporangium. Anther forms four sided structure having four microsporangia in which pollen grains are formed.

Ovule/s are located inside the ovary. The point of attachment of the ovule to the ovary is called the funicle. Funicle extends to hilum as stalk.

In an artificial hybridization program with dioecious plants:

- Bagging of the female flower: Relevant to prevent unwanted pollen contamination.
- Dusting of pollen on the stigma: Essential for pollination to occur.
- Emasculation: Not relevant because dioecious plants have separate sexes; emasculation is for monoecious plants.
- Collection of pollen: Necessary for controlled pollination process.

Therefore, in this context, the step that would not be relevant is C: Emasculation.

(C)

Pollen grains lose viability within 30 minutes of their release in some members of:

• In some cereals such as rice and wheat, pollen grains lose viability within 30 minutes of their release, and in some members of Rosaceae, Leguminoseae and Solanaceae, they maintain viability for months.

About 60% of angiosperms, pollen grains are shed at two celled stage. The larger cell is called vegetative cell and the smaller one is called generative cell. Each generative cell produces two male gametes.

The seedless fruit develops without fertilisation by using some plant hormones. The fruit so formed are called parthenocarpic.

The innermost wall layer is the tapetum. It nourishes the developing pollen grains. Cells of the tapetum possess dense cytoplasm and generally have more than one nucleus.

• True Fruit: A true fruit is one that develops only from the ovary. 
  Example: Mango, Coconut, Zizyphus etc.
• False Fruit or Pseudocarp: In some fruits, it is not the ovary that forms the fruit. In fact, some other parts of the flower, like the thalamus, inflorescence, calyx are modified to become a part of the fruit. These types of fruit are called false fruits. 
  Example: Apple, Strawberry etc.

Placenta is located inside the ovarian cavity. It help in transport of nutrient to megasporangium or ovule. Ovule is attached to placenta by means of stalk called funicle.

Bisexual flower have four main parts. Pistil or carpel is located at center followed by stamen, carpel and sepals. Pistil contains stigma, style and ovary.

Maize grain is monocotyledonous, having a single cotyledon. This cotyledon is also called scutellum.

Angiospermic embryo sac is 8-nucleate but 7-celled at maturity. This includes 3- celled egg Synergids, 3 antipodal cells and 2 polar nuclei.

The synergids have special cellular thickenings at the micropylar tip called filiform apparatus, which play an important role in guiding the pollen tubes into the synergid.

• Fertilization is the most important event in sexual reproduction.
• It is the process of fusion of 2 haploid gametes of different sex, forming one single diploid zygote.
• Also known as syngamy.

• Nucellus: The tissue within the ovule where megagametogenesis occurs.

• Megaspore mother cell (Megaspore mother cell): The diploid cell in the nucellus that undergoes meiosis to form a megaspore tetrad.

• Megaspore tetrad: The four haploid megaspores resulting from meiosis of the megaspore mother cell.

• Megaspore: Typically, three of the four megaspores degenerate, leaving one functional megaspore.

• Female gametophyte: The functional megaspore undergoes mitotic divisions to form the female gametophyte (embryo sac).

Thus, the correct sequence is: Nucellus → Megaspore mother cell → Megaspore tetrad → Megaspore → Female gametophyte.

Lotus is an aquatic plant but the flower of lotus is outside and above the water surface. So, it cannot be pollinated by water. It is generally pollinated by insects.

• Endospermic: Castor seeds contain endosperm, which is the tissue that provides nourishment to the developing embryo.

• Albuminous: The endosperm in castor seeds remains in the mature seed and is not consumed during seed development, so it is termed albuminous.

(a) Tetrasporangiate: Correct. A typical anther has four pollen sacs or microsporangia.

(b) Tetragonal: Correct - The anther is a four-sided (tetragonal) structure consisting of four microsporangia located at the corners, two in each lobe.

(c) Trilobed: No, anthers are typically bilobed, not trilobed

(d) Surrounded by four wall layers: Correct. The anther is surrounded by four distinct wall layers: the epidermis, endothecium, middle layer, and tapetum.