Q.Can you think of how tapetal cells could become bi-nucleate?
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.
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
Without the male and female gametophytes, no seed would form, and no fruit would develop. In flowering plants, the male gametophyte is the pollen that bees carry, wind blows, or humans collect for pollination. The female gametophyte is the hidden, protected structure inside the ovary. Their meeting is the moment of fertilisation — the start of a new plant’s life.
For a commerce or humanities student, the key takeaway is this: gametophytes are the tiny, single-generation carriers of genetic material in plants. They are not the visible flower parts — they are the microscopic “packages” that ensure reproduction. In NCERT, this concept is the foundation for understanding pollination, fertilisation, and seed formation. It’s a simple but powerful idea: life passes from one generation to the next through these miniature, specialised cells.
Students revising this topic often search for "Male And Female Gametophyte NEET questions", "Male And Female Gametophyte important questions", or "Male And Female Gametophyte class 12 biology". This concept is directly part of the Sexual Reproduction in Flowering Plants chapter in the NCERT/CBSE Class 12 Biology syllabus, and it is also an important topic for NEET and state medical/CET entrance exams, making it worth mastering for both board and competitive-exam preparation.
Tapetal cells often become bi-nucleate (or multinucleate) through nuclear division without accompanying cytokinesis — the nucleus divides (mitotically, or sometimes via endomitosis, where the chromosomes replicate without any spindle/nuclear division at all) but the cell itself does not split into two daughter cells. The result is a single tapetal cell containing two (or more) nuclei, which increases its metabolic capacity to nourish the developing microspores.
Tapetal cells become bi-nucleate when their nucleus divides but the cell does not undergo cytokinesis — nuclear division outpaces cell division.
Tapetal cells become bi-nucleate because their nucleus can divide without the cell itself dividing — nuclear division runs ahead of cytokinesis.
The tapetum is the innermost, nutritive wall layer of the microsporangium (§1.2.1) — its job is to nourish the developing pollen mother cells and microspores, which demands a high level of metabolic activity. One well-documented way tapetal cells meet this demand is by becoming bi-nucleate or multinucleate:
- The tapetal cell's nucleus undergoes mitotic division in the normal way — the chromosomes replicate and the nucleus splits into two daughter nuclei.
- However, cytokinesis (division of the cytoplasm into two separate cells) does not follow. The cell wall/membrane never divides.
- The result is a single tapetal cell now containing two nuclei side by side in one shared cytoplasm.
- In some cases this can repeat, or the nucleus can undergo endomitosis (chromosome replication with no spindle formation and no nuclear division at all), which increases the cell's ploidy without changing the nucleus count — a related but distinct route to a more metabolically active tapetal cell.
Both routes serve the same purpose: a bi-/multi-nucleate (or higher-ploidy) tapetal cell has more genetic material actively directing protein synthesis, supporting its role in nourishing the pollen grains as they develop.
By nuclear division (mitosis) occurring without a following cytokinesis — the nucleus splits into two but the cell does not, leaving one tapetal cell with two 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)
- d = Mitosis (three mitotic divisions of the functional megaspore)
NoteThe NCERT textbook for Class 12 Biology (Chapter 2, Sexual Reproduction in Flowering Plants) explicitly states: "The megaspore mother cell undergoes meiotic division to produce four haploid megaspores. Usually, only one of them is functional while the other three degenerate." It then adds: "The functional megaspore enlarges and undergoes three mitotic divisions to form an eight-nucleate embryo sac."
ImportantA common mistake is to think that the MMC divides by mitosis first, or that all four megaspores participate in forming the embryo sac. Neither is correct. The MMC always undergoes meiosis, and only one megaspore survives to undergo mitosis.
✓Final answerThe correct option is (B) a – Meiosis-I, b – Meiosis-II, c – No division, d – Mitosis. This sequence exactly follows the NCERT description: the megaspore mother cell undergoes meiosis to produce four megaspores, three degenerate without dividing, and the single functional megaspore then undergoes mitosis to form the embryo sac.
- 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 why pollen grains are so well preserved as fossils. Pectin, cellulose and chitin are far less resistant.
✓Final answer(C) Sporopollenin.
- 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 gametes. Antipodal cells are part of the female embryo sac, not the pollen grain.
✓Final answer(D) Both (A) and (B) — Vegetative cell and Generative cell.
- 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 two male gametes. Antipodals, the central cell and the micropyle (an opening) do not perform this guiding function.
✓Final answer(B) Filiform apparatus.
- 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 apparatus is drawn as hatched lines), label A (the middle pair of nucleated cells) corresponds to the two polar nuclei of the central cell, and label B (the cluster of three cells nearest the filiform apparatus) corresponds to the egg apparatus (egg cell + 2 synergids).
✓Final answerA = polar nuclei (of the central cell); B = egg apparatus (egg cell + 2 synergids).
- 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.
- The generative cell divides mitotically (once, either before shedding in some species, or inside the growing pollen tube in others) to produce the two non-motile male gametes.
The microspore mother cell (PMC) undergoes meiosis to produce the four haploid microspores in the first place, and the megaspore mother cell is on the female side (ovule) — neither directly forms male gametes.
✓Final answer(b) Generative cell.
- 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.
Role: The filiform apparatus plays a crucial role in guiding the growing pollen tube towards the embryo sac. It helps direct the pollen tube precisely into one of the synergids, ensuring the pollen tube enters through the micropyle and releases its two male gametes into the correct synergid (a process aided by chemotropic attraction). This precise guidance is essential for successful double fertilisation, where one male gamete fuses with the egg (forming the zygote) and the other fuses with the two polar nuclei (forming the triploid endosperm nucleus).
✓Final answerThe filiform apparatus is located at the micropylar tip of the synergid cells within the embryo sac; it guides/directs the entry of the pollen tube into the synergid, helping deliver the male gametes for double fertilisation.
- 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 months when stored (this is exploited to build pollen banks, similar to seed banks, for crop breeding).
✓Final answerOption (b): (i) Solanaceae, (ii) Leguminosae, (iv) Rosaceae.
- 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 2 × 2 = 4 microsporangia in the whole anther. These microsporangia later develop into pollen sacs filled with pollen grains at maturity.
✓Final answerOption (d): 2 thecae, 4 sporangia (microsporangia/pollen sacs).
- 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:
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1 egg cell (oosphere) — the female gamete, located in the centre, flanked by the two synergids.
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2 synergid cells — flanking the egg cell on either side. Each synergid has special cellular thickenings at the micropylar tip called the filiform apparatus, which helps guide the entry of the pollen tube into the embryo sac (chemotropism).
✓Final answer(c) 2 synergid cells + 1 egg cell.
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- 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).
- The other male gamete fuses with the two polar nuclei → forms the triploid primary endosperm nucleus (PEN) (triple fusion).
Synergids and antipodal cells play supportive/nutritive roles and do not fuse with the male gamete to form the zygote.
✓Final answer(a) Egg Cell.
- 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 the two synergids together with the one egg cell — the antipodal cells (option a) and the polar nuclei with the egg cell (option d) do not match this specific structure.
✓Final answer(c) Synergids and one egg cell
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