Starting from the innermost part, the correct sequence of parts in an ovule are: (a) egg, nucellus, embryo sac

NCERT Exemplar · Q8

Q. Starting from the innermost part, the correct sequence of parts in an ovule are:

(a) egg, nucellus, embryo sac, integument

(b) egg, embryo sac, nucellus, integument

(d) egg, integument, embryo sac, nucellus

Kerala DhseMCQ· 1mImportance★★★★★

49% · 44/90 Questions

🔒 Locked · start free trial →

You're viewing a preview — the full solution, concept, methods & PYQ mapping are locked.

Start your 14-day free trial to unlock the full solution →

Concept understanding — Male And Female Gametophyte

Let’s start with something you already know. Think of a plant like a mango tree. It produces flowers, and those flowers eventually turn into mangoes. How does that happen? The flower is the plant’s reproductive organ, and inside it, two tiny but crucial structures are made: the male gametophyte and the female gametophyte. These are not the “male” and “female” parts of the flower themselves (like the stamen and pistil) — they are the microscopic, single-generation cells that actually carry the genetic material to form the next plant.

The everyday intuition

Imagine you are baking a cake. The male gametophyte is like the packet of dry yeast — it’s small, mobile, and needs to be added to the mixture. The female gametophyte is like the bowl of flour, eggs, and sugar — it’s larger, stationary, and provides the environment where the yeast works. Without the yeast reaching the bowl, no cake rises. Without the bowl, the yeast has nothing to act on. In a flower, the male gametophyte (pollen grain) must travel to the female gametophyte (embryo sac) for fertilisation to happen.

The precise meaning

In NCERT biology, the male gametophyte is the pollen grain. It develops inside the anther (the top part of the stamen). A mature pollen grain contains two cells: a tube cell and a generative cell. The tube cell will grow a long tube down the style of the pistil, and the generative cell will divide to form two sperm cells. So the male gametophyte is not the whole stamen — it’s the tiny, single-celled (or two-celled) structure that carries the male genetic material.

The female gametophyte is the embryo sac. It develops inside the ovule, which is located in the ovary of the pistil. The embryo sac is a seven-celled, eight-nucleate structure (though you don’t need to memorise numbers for a prose subject — just know it’s a small, organised sac). It contains the egg cell (the female gamete) and other cells that help in fertilisation and nourishment. The female gametophyte is not the whole pistil — it’s the microscopic sac inside the ovule.

Important

The male gametophyte (pollen grain) is haploid — it has only one set of chromosomes. The female gametophyte (embryo sac) is also haploid. When they fuse during fertilisation, they form a diploid zygote, which grows into the seed. This is why both are called “gametophytes” — they produce gametes (sperm and egg).

Why it matters …

Start your 14-day free trial to unlock the full solution →

Starting from the innermost part, the correct sequence of parts in an ovule is the egg cell, followed by the embryo sac, then the nucellus, and finally the integuments.

Flowering plants, or angiosperms, exhibit a fascinating and intricate process of sexual reproduction. Central to this process is the formation of gametes, which occurs within specialized structures known as gametophytes. These gametophytes represent the haploid generation in the plant's life cycle, responsible for producing the actual reproductive cells.

In angiosperms, the gametophytes are highly reduced and dependent on the sporophyte (the main plant body). The male gametophyte is the pollen grain, which develops within the anther of a stamen. It carries the male gametes. The female gametophyte, on the other hand, is known as the embryo sac, and its development and protection occur within a specialized structure called the ovule, located inside the ovary. Understanding the structure of the ovule is crucial to comprehending female gamete formation and subsequent fertilization.

An ovule is a small, oval structure typically attached to the placenta inside the ovary. It is the site where the female gametophyte, or embryo sac, develops. Let us examine its key components, moving from the outermost protective layers to the innermost reproductive cell.

Integuments: These are one or two protective envelopes that surround the main body of the ovule. They provide protection to the developing embryo sac and later mature into the seed coat after fertilization. At one end, the integuments leave a small opening called the micropyle, which facilitates the entry of the pollen tube during fertilization.
Nucellus: Enclosed within the integuments is a mass of parenchymatous cells called the nucellus. This tissue is rich in reserve food material and provides nourishment to the developing embryo sac. The nucellus is the primary tissue from which the megaspore mother cell differentiates.
Embryo Sac (Female Gametophyte): Deep within the nucellus, typically embedded in its central part, lies the embryo sac. This is the actual female gametophyte. In most flowering plants, the embryo sac is formed from a single functional megaspore and is typically seven-celled and eight-nucleate at maturity. It contains all the structures necessary for fertilization.
Egg Cell: Within the embryo sac, at the micropylar end, is a group of three cells known as the egg apparatus. This apparatus consists of two synergids and one egg cell. The egg cell is the actual female gamete, ready to fuse with a male gamete from the pollen tube to form the zygote. The synergids play a role in guiding the pollen tube towards the egg cell. …

Start your 14-day free trial to unlock the full solution →

←Previous questionQ7 — From among the sets of terms given below, identify those that are asso…→Next questionQ9 — From the statements given below choose the option that are true for a …

Q.Starting from the innermost part, the correct sequence of parts in an ovule are:

🎓Unlock everything free for 14 days

Unlock everything free for 14 days