Test: Post-Fertilization (Structures & Events) - NEET MCQ

In coconut (Cocos nucifera), the surrounding white kernel called coconut meal is cellular endosperm and the coconut water (also called coconut milk) in the centre is free nuclear endosperm made up of thousands of nuclei.

After fertilisation, the integuments of the ovule form the protective coats (seed coats). Outer integument develops into testa and the inner one develops into tegmen.

• The epicotyl bearing shoot apex and leaf primordia are enclosed in a foliar structure called coleoptile. It protects the plumule during emergence from the soil.
• The radicle is protected in a sheath called coleorhiza. It protects the radicle during its passage into the soil.
• So, the correct answer is " radicle, plumule ".

Given figure represents the monocotyledonous embryo of a grass.

(D) only 1 

Occasionally, in some seeds such as black pepper and beet, remnants of nucellus are also persistent. This residual, persistent nucellus is the perisperm.

As ovules mature into seeds, the ovary develops into a fruit, i.e., the transformation of ovules into seeds and ovary into fruit proceeds simultaneously. The wall of the ovary develops into the wall of fruit called pericarp.

Although in most of the species, fruits are the results of fertilisation, there are a few species in which fruits develop without fertilisation. Such fruits are called parthenocarpic fruits. Banana is one such example. Parthenocarpy can be induced through the application of growth hormones and such fruits are seedless.

The micropyle is a small pore in the seed coat that facilitates the entry of water and air into the seed during germination. It does not have a role in the entry of pollen or fertilization tubes, which are related to the fertilization process prior to seed formation.

In the most common type of endosperm development:

- The PEN undergoes successive nuclear divisions to give rise to free nuclei.
- Subsequently, cell wall formation occurs.

This process implies that the initial divisions of the PEN do not involve cell wall formation; instead, the formation of free nuclei precedes cell wall development. This sequence is a fundamental aspect of endosperm development, ensuring the creation of a structured cellular framework during this critical stage of plant growth.

(B) The correct answer is B: Globular embryo, Heart-shaped embryo, Mature Embryo.

- Globular embryo: At this stage, the embryo is spherical in shape.
- Heart-shaped embryo: The embryo develops into a heart shape as it matures.
- Mature Embryo: This is the final stage where the embryo is fully developed and ready for seed formation.

Understanding these stages helps track the growth of a dicot embryo from its early spherical form to its mature, seed-forming stage.Globular embryo, Heart shaped embryo, Mature Embryo

In angiosperms, endosperm is a triploid structure.
∴ 3n = 24 (given), then n = 8
As gametes are haploid structures, therefore number of chromosomes in gametes is 8

After entering one of the synergids, the pollen tube releases the two male gametes into the cytoplasm of the synergid. One of the male gametes moves towards the egg cell and fuses with its nucleus thus completing the syngamy. This results in the formation of a diploid cell, the zygote. The other male gamete moves towards the two polar nuclei located in the central cell and fuses with them to produce a triploid primary endosperm nucleus (PEN).

Correct option is D. A-Seed coat, B-Endosperm, C-Cotyledon, D-Hypocotyl

In some seeds, remains of nucellus persist. This residual nucellus which persists in the seed is called perisperm, e.g., black pepper, coffee, castor, cardamum, Nymphaea.

Endosperm development precedes embryo development because the endosperm provides nutrients to the developing embryo: 

• Endosperm formation

  During double fertilization, one sperm nucleus enters the embryo sac and fuses with two polar nuclei to create the endosperm. 

• Endosperm function

  The endosperm provides nutrients to the embryo, protects it, and controls its growth. In mature albuminous seeds, the endosperm stores starch and fat.

Nuclear endosperm (X) is the most common type of endosperm. It is named so because it contains free nuclei in the beginning. The primary endosperm nucleus divides of free nuclei. Meanwhile central vacuole appears in the central cell and pushes the cytoplasm containing the nuclei to the periphery. The cytoplasm thickens so that the vacuole decreases in size. It ultimately disappears with the exception of a few cases. The multinucleate cytoplasm undergoes cleavage and gives rise to a multicellular tissue, e.g., maize, wheat, rice, sunflower, Capsella bursa-pastoris.