Test: Sexual Reproduction in Flowering Plants - 3 - NEET MCQ

• Apomixis in flowering plants is defined as the asexual formation of a seed from the maternal tissues of the ovule, avoiding the processes of meiosis and fertilization, leading to embryo development. 
• Apomixis relates to mechanisms where an embryo sac is mitotically formed from a diploid cell in the ovule, bypassing meiosis. The genetic nature of plants produced by apomictic embryos is the same as that of parents so they can be called clones.
• Hence, the mother cell is diploid, so diploid embryo forms.

Pollen wall consists of two layers: outer layer exine and inner layer intine.

Exine is made up of sporopollenin which is one of the most resistant known biological materials. Exine is thin in the beginning but it becomes very thick with maturity. However, exine is discontinuous or ruptured at some places. These are the called the germ pores (or germinal furrow) through which pollen tube comes out during germination on the stigma.

• The protoplast of the male gametophyte divides mitotically to produce two unequal cells; a small generative cell and a large vegetative cell.
• The generative cell divides into two non-motile male gametes (or sperms).
• Thus, the male gametophyte in angiosperms produces two sperms and a vegetative cell.
• The vegetative cell, later on grows to produce pollen tube.

Statement 1: Pollination does not guarantee fertilization; it is merely the transfer of pollen to the stigma. Post-pollination events, including pollen-pistil interaction, must occur to ensure fertilization.
Statement 2: The sequence of events from pollen deposition on the stigma until the pollen tubes enter the ovule is correctly referred to as pollen-pistil interaction. This statement is correct.
Statement 3: Pollen-pistil interaction involves both the promotion and rejection of pollen, depending on compatibility. Therefore, the statement that it involves only promotion is incorrect.
Statement 4: Pistils do have the ability to recognize pollen and can discriminate between compatible and incompatible pollen types.
Thus, Statement 2 is the correct option.

Hilum is the junction between the ovule and funicle (2).
Integuments are the protective envelopes encircling the nucellus (3).
Micropyle is the small opening at the tip of the ovule (1).
Chalaza is the basal part of the ovule, opposite the micropyle (4).
Nucellus is the mass of cells inside the ovule with abundant reserve food materials (5).
Therefore, the correct matches are A - 2, B - 3, C - 1, D - 4, and E - 5.

(In artificial hybridization, the correct answer is B: (b), (c), and (d) only. Here's why:

- (b): Emasculation is crucial to prevent self-pollination and ensure only desired pollen reaches the stigma.
- (c): Bagging emasculated flowers post-cross-pollination shields them from unwanted pollen.
- (d): Bagging after anther removal further secures the controlled pollination process by preventing accidental self-pollination.

These steps collectively ensure successful artificial hybridization by controlling pollination and fertilization processes effectively.B)

(C) Pollen tablets are available in the market for supplementing food. Here's why:

- Supplementing Food: Pollen tablets are commonly used as a nutritional supplement due to their rich content of proteins, vitamins, minerals, and antioxidants.

- They can enhance the nutritional value of one's diet, especially for individuals who may have specific dietary deficiencies or require additional nutrients.

- These tablets are not primarily associated with in vitro fertilization, breeding programs, or ex situ conservation, but rather serve as a dietary supplement for human consumption.

In pea, bean and groundnut, endosperm is consumed by developing embryo in the seed. The endosperm is completely absorbed by the growing embryo and the food reserve gets stored in the cotyledons. Such seeds are called non-endospermic or exalbuminous.

Answer: B

The correct answer is: A-Meiosis-I, B-Meiosis-II, C-No division, D-Mitosis.

• A: Meiosis-I reduces the chromosome number by half, creating two haploid cells from a diploid cell.


• B: Meiosis-II separates the sister chromatids, resulting in four haploid cells.


• C: No division indicates no further cell division occurs at this stage.


• D: Mitosis produces two identical daughter cells, maintaining the chromosome number.


 

During microsporogenesis, meiosis occurs in Microspore Mother Cell (MMC) and four haploid microspores (microspore tetrad) are formed.

• The period in which the pollen grains remain viable is highly variable.
• It depends on the temperature and humidity.

Maize which is also known as Corn plant is pollinated by wind. The anthers are born in long tassels that move with the wind and shake off their pollen. The stigma is feathery and hairy so as to catch the wind-borne pollen. Thus, in maize, pollens are transferred from the anthers of one plant to the stigma of another plant by means of wind i.e. cross-pollination occurs by the wind.

• The diagram represents the multicarpellary, syncarpous pistil of Papaver.
• The gynoecium of this plant consists of more than one pistil, showing multicarpellary condition.
• These pistils are fused together and hence are called syncarpous.

Explanation:
- Statement 1: Pollination by water is quite rare in flowering plants.
- This statement is correct because most flowering plants rely on animals like insects, birds, or mammals for pollination rather than water.
- Statement 2: All aquatic plants use water for pollination.
- This statement is incorrect because not all aquatic plants use water for pollination. Many aquatic plants rely on insects or wind for - 

STATEMENT 3 :pollination.In most water-pollinated species, pollen grains are protected from wetting by a mucilaginous covering. This helps in preventing the pollen from getting damaged by water.                                                                                                         

 STATEMENT 4 : Plants like Water Hyacinth and Water Lily are not pollinated by water; they use insects or wind for pollination.

The correct answer is D: 1 AND 3 BOTH

Statement 1: This is correct. Non-albuminous seeds have no residual endosperm, as it is completely consumed during embryo development, while albuminous seeds retain some endosperm.
Statement 2: This is incorrect. The perisperm is a residual, persistent nucellus, not a type of endosperm, and is found in seeds like black pepper and beet, not wheat and maize.
Statement 3: This is incorrect. Cotyledons are generally thick and swollen due to the storage of food reserves.
Statement 4: This is incorrect. The micropyle facilitates the entry of water and oxygen into the seed during germination, not the exit of water.
Therefore, Statement 1 is the correct statement regarding seed characteristics and development.