Q.Explain the 8-nucleate mature embryo sac of a typical angiospermic flower with the help of a labelled diagram only.
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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.
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 …
The mature embryo sac (female gametophyte) is 7-celled but 8-nucleate: three antipodals, one central cell with two polar nuclei, and the egg apparatus (one egg + two synergids). A labelled diagram shows these at the two poles. …
Mature angiosperm embryo sac = 7-celled, 8-nucleate: 3 antipodals + central cell (2 polar nuclei) + egg apparatus (1 egg + 2 synergids).
Concept: The functional megaspore undergoes three successive free-nuclear mitotic divisions producing 8 nuclei (4 at each pole), which are then organised, with cell walls, into a 7-celled female gametophyte.
Structure to label in the diagram:
- Micropylar end — the egg apparatus: one large egg cell (oosphere) flanked by two synergids bearing a filiform apparatus that guides the pollen tube.
- Centre — a large central cell containing two polar nuclei. …
Showing the 12 most recent of 60 on this concept.
- CBSE 2026Set 57/2/11 markMCQQ.Given below are stages of embryo sac formation from megaspore mother cell. Identify the correct option for the cell division marked a, b, c and d. (A) a – Meiosis-I, b – No division, c – Mitosis, d – Meiosis-II (B) a – Meiosis-I, b – Meiosis-II, c – No division, d - Mitosis (C) a – Mitosis, b – Meiosis-I, c – Meiosis-II, d – No division (D) a – No division, b – Mitosis, c – Meiosis-I, d – Meiosis-II
›Reveal solutionSolution
The megaspore mother cell undergoes meiosis (two divisions) to produce four haploid megaspores, of which only one survives; that functional megaspore then undergoes three mitotic divisions to form the eight-nucleate embryo sac — so the correct sequence is Meiosis-I, Meiosis-II, No division, Mitosis.
To understand this question, you need to picture the sequence of events inside the ovule of a flowering plant. The story begins with a single, large cell called the megaspore mother cell (MMC) . This cell is diploid (2n) and is the starting point for forming the female gametophyte — the embryo sac.
The MMC does not simply grow or divide by mitosis. Instead, it enters meiosis, a special type of cell division that reduces the chromosome number by half. Meiosis happens in two consecutive stages: Meiosis-I and Meiosis-II. So the very first division (marked 'a' in your diagram) is Meiosis-I. The second division (marked 'b') is Meiosis-II. After these two divisions, the original single MMC has produced four haploid (n) cells — these are called megaspores.
Now here is a critical twist. In most flowering plants, three of these four megaspores degenerate and die. Only one of them — usually the one farthest from the micropyle (the opening of the ovule) — remains functional. So after the four megaspores are formed, there is a stage where no division occurs (marked 'c' in your diagram). Instead, three cells simply break down, leaving just one functional megaspore.
That single functional megaspore is the starting point for the actual embryo sac. It is haploid and now needs to grow into a structure that contains the egg cell and other supporting cells. How does it do that? It undergoes three rounds of mitotic divisions (marked 'd'). Mitosis ensures that all the resulting nuclei remain haploid and genetically identical. The first mitosis produces two nuclei, the second produces four, and the third produces eight nuclei. These eight nuclei then arrange themselves into the typical seven-celled, eight-nucleate embryo sac (with the egg apparatus, central cell, and antipodal cells).
So, mapping this to the labels in your question:
- a = Meiosis-I (first reduction division)
- b = Meiosis-II (second division, producing four megaspores)
- c = No division (three megaspores degenerate) …
- CBSE 2026Set A1 markMCQQ.Which of the following is one of the most resistant organic materials?(a) Pectin(b) Cellulose(c) Sporopollenin(d) Chitin
›Reveal solutionSolution
Sporopollenin forms the pollen exine and is among the most resistant organic materials known.
The hard outer wall (exine) of a pollen grain is made of sporopollenin. It can withstand high temperatures and strong acids and alkalis, and no enzyme is known that can degrade it. This extreme resistance is wh …
- CBSE 2026Set A1 markMCQQ.Which of the following cells is present in pollen grain of angiospermic plants?(a) Vegetative cell(b) Generative cell(c) Antipodal cell(d) Both (A) and (B)
›Reveal solutionSolution
An angiosperm pollen grain (male gametophyte) contains a vegetative cell and a generative cell.
When a pollen grain is shed, it is usually at the 2-celled stage. It contains a large vegetative (tube) cell with abundant food reserves, and a small generative cell floating within its cytoplasm. The generative cell later divides to form two male ga …
- CBSE 2026Set A1 markMCQQ.Which of the following plays an important role in guiding the pollen tube into the synergids?(a) Antipodals(b) Filiform apparatus(c) Central cell(d) Micropyle
›Reveal solutionSolution
The filiform apparatus of the synergids guides the entering pollen tube into a synergid.
At the micropylar end of the embryo sac, the synergids bear special cellular thickenings called the filiform apparatus. This structure guides the pollen tube by directing its entry into one of the synergids. Once inside, the pollen tube bursts and releases the …
- CBSE 2026Set ANNUAL1 markQ.What does 'A' and 'B' represent in the above mentioned diagram of the mature embryosac? Write name for each.
›Reveal solutionSolution
In the mature 7-celled, 8-nucleate embryo sac, A marks the two polar nuclei of the central cell and B marks the three-celled egg apparatus (2 synergids + 1 egg cell) at the micropylar end.
A typical angiosperm embryo sac at maturity has 7 cells and 8 nuclei, organised as: 3 antipodal cells at the chalazal end; a large central cell containing 2 polar nuclei (which fuse with a male gamete during triple fusion to form the triploid endosperm); and, at the micropylar end, the egg apparatus consisting of 1 egg cell flanked by 2 synergid cells. The synergids bear a special thickened structure at their micropylar tip called the filiform apparatus, which guides entry of the pollen tube into the embryo sac. In the given figure, going from the chalazal end (top, unlabelled antipodal cells) toward the micropylar end (bottom, where the filiform a …
- CBSE 2026Set ANNUAL1 markMCQQ.Male gametes in angiosperms are formed by the division of(a) Vegetative cell(b) Generative cell(c) Microspore mother cell(d) Megaspore mother cell
›Reveal solutionSolution
The pollen grain's generative cell divides mitotically to form two non-motile male gametes that are delivered through the pollen tube.
A mature pollen grain in angiosperms is typically 2-celled at shedding: a larger vegetative (tube) cell and a smaller generative cell, floating within the vegetative cell's cytoplasm.
- The vegetative cell has abundant food reserves and, upon germination on the stigma, forms the pollen tube that grows down through the style. …
- CBSE 2026Set ANNUAL1 markQ.Where is filiform apparatus located? What is the role of filiform apparatus?
›Reveal solutionSolution
The filiform apparatus is a set of finger-like cell-wall thickenings at the micropylar end of each synergid, and it functions to guide the entry of the pollen tube into the embryo sac.
Location: Within the mature embryo sac of an angiosperm ovule, two synergid cells flank the egg cell at the micropylar end (together forming the egg apparatus). Each synergid has specialised, finger-like thickenings of its cell wall at its micropylar tip called the filiform apparatus.
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- CBSE 2026Set ANNUAL1 markMCQQ.Pollen grains retain viability for months in plant belonging to different families given below :(i) Solanaceae(ii) Leguminosae(iii) Gramineae(iv) Rosaceae(v) Liliaceae Correct option is :(a) (i),(ii) &(v)(b) (i),(ii) &(iv)(c) (ii), (iv),(v)(d) (i), (iii), (v)
›Reveal solutionSolution
Pollen viability varies enormously by species — from 30 minutes in some cereals to months in members of Solanaceae, Leguminosae and Rosaceae.
Pollen grain lifespan depends on temperature and humidity. In many members of the family Poaceae (Gramineae) pollen viability is lost within 30 minutes of release, while in some members of Solanaceae, Leguminosae, and Rosaceae, pollen grains maintain viability for …
- CBSE 2026Set ANNUAL1 markMCQQ.The structure of bilobed anther consist of :(a) 2 thecae, 2 sporangia(b) 4 thecae, 4 sporangia(c) 4 thecae, 2 sporangia(d) 2 thecae, 4 sporangia
›Reveal solutionSolution
A typical anther is bilobed and dithecous: two lobes (thecae), each theca bearing two microsporangia (pollen sacs) — four microsporangia in total.
A mature anther consists of two lobes joined by a sterile connective. Each lobe is called a theca, so a bilobed anther has 2 thecae, making it 'dithecous'. Within each theca lie two elongated sac-like structures called microsporangia (pollen sacs), running almost the full length of the anther. So each theca contributes 2 microsporangia, giving …
- CBSE 2026Set ANNUAL1 markMCQQ.Egg apparatus is made up of :(a) 2 synergid cells + 2 egg cells(b) 1 synergid cell + 2 egg cells(c) 2 synergid cells + 1 egg cell(d) 1 synergid cell + 1 egg cell
›Reveal solutionSolution
The egg apparatus, sitting at the micropylar end of the embryo sac, is made up of 2 synergid cells + 1 egg cell.
The mature female gametophyte (embryo sac) of a flowering plant is typically 7-celled and 8-nucleate. At its micropylar end lies a group of three cells called the egg apparatus, consisting of:
- 1 egg cell (oosphere) — the female gamete, located in the centre, flanked by the two synergids. …
- CBSE 2026Set ANNUAL1 markMCQQ.During fertilization, which cell fuses with male gamete to form zygote?(a) Egg Cell(b) Polar Cell(c) Synergid(d) Antipodal Cell
›Reveal solutionSolution
Syngamy (fusion of the egg cell with one male gamete) forms the diploid zygote; the other male gamete fuses with the polar nuclei (triple fusion) to form the endosperm — together this is double fertilization.
In the mature embryo sac, the egg apparatus consists of one egg cell flanked by two synergids, with three antipodal cells at the chalazal end and two polar nuclei in the central cell. When the pollen tube discharges its two male gametes into a synergid:
- One male gamete fuses with the egg cell → forms the diploid zygote (syngamy). …
- CBSE 2026Set ANNUAL1 markMCQQ.Which of the following cells are present in the egg apparatus?(a) Antipodal cells(b) Synergids(c) Synergids and one egg cell(d) Polar nuclei and one egg cell
›Reveal solutionSolution
The egg apparatus at the micropylar end of the embryo sac is made up of two synergids flanking a single central egg cell.
A mature (7-celled, 8-nucleate) angiosperm embryo sac has three cell groups: the egg apparatus at the micropylar end (consisting of two synergid cells and one egg cell), three antipodal cells at the chalazal end, and a large central cell containing two polar nuclei. Since the question asks specifically about the cells present in the egg apparatus, the answer is t …
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