Test: Pre Fertilisation: Structures & Events - NEET MCQ

The assertion correctly states that the stigma serves as a landing platform for pollen grains. The reason also correctly states thatThe stigma is adapted with a sticky or receptive surface that helps capture and hold pollen grains for fertilization., providing a logical explanation for the assertion.

The correct answer is: (A)
In the given enlarged view of the microsporangium, the layers are identified as follows:
- A: Epidermis - the outermost protective layer
- B: Endothecium - the specialized cell layer surrounding the sporogenous tissue
- C: Middle layers - various layers lying between the endothecium and tapetum
- D: Tapetum - the innermost layer responsible for nourishing developing pollen grains

• The exine of the pollen grain is made of sporopollenin. Sporopollenin is one of the most resistant organic compounds.
• It can withstand high temperature, strong acids, and alkalis and cannot be degraded by any of the known enzymes.
• Hence, it acts as a shield and protects the pollen grain from getting damaged.

Structure of pollen grain:

Hence the correct option is 'A' 

Starting from the innermost part, the correct sequence of parts in an ovule is egg, Embryosac,  nucellus, integument. This sequence can be seen in following

  A diagrammatic view of an ovule 

A. Monocarpellary:
- This term refers to the condition where the gynoecium (the female parts of a flower) consists of a single pistil.
- A pistil is a single or fused carpel, and the carpel is the individual unit of the gynoecium.
- Hence, option A (Monocarpellary) matches with 2 (Refers to the condition where gynoecium consists a single pistil).
B. Syncarpous:
- This term is used to describe the condition where multiple pistils are fused together.
- The pistils could be completely fused, or they could maintain separate ovaries but share a common style or stigma.
- Therefore, option B (Syncarpous) matches with 1 (Refers to the condition where pistils are fused together).
C. Micropyle:
- Micropyle is a small opening in the ovule of a seed plant.
- It's through this opening that the pollen tube enters during fertilization.
- The micropyle allows for the sperm cells carried within the pollen tube to reach the ovule and fertilize it, leading to the formation of a seed.
- As a result, option C (Micropyle) matches with 3 (The small opening in the ovule through which pollen tubes enter).

So, the correct matching is: A - 2, B - 1, C - 3. Therefore, the answer is D.

The correct answer is: D: Statement I is incorrect, Statement II is incorrect.

- The spindle formation as seen in Asymmetric during microspore maturation.
- The larger cell (B) is  the vegetative cell, and the smaller cell (C) is  the generative cell. 

Explanation: In monosporic development, only one megaspore out of the four produced from the megaspore mother cell (MMC) develops into the female gametophyte. The other three megaspores typically degenerate. Therefore, the assertion is correct. However, the reason is incorrect as it states that all four megaspores become functional, which is not the case in monosporic development.

Here's a detailed explanation:

- The diagram depicts the different stages of embryo sac development.
- Statement I is correct because it accurately describes the content of the diagram, showing two, four, and eight nucleate stages of the embryo sac.
-  Statement II is correct as the divisions in embryo sac development are typically  free nuclear.

 

A synergid cell wall forms a highly thickened structure called the filiform apparatus at the micropylar end consisting of numerous finger-like projections into synergid cytoplasm. These synergid cells are necessary for pollen tube guidance in the ovule.

The female gametophyte in angiosperms plants is called Embryo sac.

The female gametophyte of flowering plants, which produces the two female gametes – the egg cell and central cell – for double-fertilization by the two sperm cells of the male gametophyte (pollen grain).

Hence the correct option is 'C'