BiologyCBSE Class 12 · Sexual Reproduction in Flowering Plants

Microsporogenesis and the Pollen Grain

Updated 15 October 2026 · Fact-checked

Microsporogenesis is the formation of microspores from a pollen mother cell (PMC) by meiosis inside the microsporangium of an anther. Each diploid PMC gives a tetrad of four haploid microspores, which mature into pollen grains. A pollen grain is the male gametophyte: a vegetative cell and a generative cell inside a sporopollenin exine and cellulose-pectin intine.

Understand Microsporogenesis and the Pollen Grain

Where it happens. A stamen has a long, slender filament and a terminal anther. A typical angiosperm anther is bilobed, and each lobe has two theca (it is *dithecous*); a groove often runs lengthwise between the theca. In transverse section the anther is four-sided (tetragonal) with four microsporangia, two in each lobe, at its corners. The microsporangia grow into pollen sacs packed with pollen grains.

The wall of a microsporangium (nearly circular in section) has four layers, from outside in:
1. Epidermis
2. Endothecium
3. Middle layers
4. Tapetum (innermost)
The outer three protect the sporangium and help the anther split open (dehiscence) to release pollen. The tapetum nourishes the developing pollen grains; its cells have dense cytoplasm and generally more than one nucleus. When the anther is young, the centre is filled with sporogenous tissue: compactly arranged, similar-looking cells.

Microsporogenesis. As the anther develops, each sporogenous cell can act as a pollen mother cell (PMC) or microspore mother cell. A PMC is diploid (2n) and undergoes meiosis to form a cluster of four haploid (n) cells, the microspore tetrad. As the anther matures and dries, the microspores separate from each other and develop into pollen grains. Each microsporangium forms thousands of them.

Flow chart:
sporogenous tissue (2n) → pollen mother cell (2n) → *meiosis* → microspore tetrad (4 × n) → separate microspores (n) → pollen grains (n) → anther dehisces, pollen released.

The pollen grain = male gametophyte. Pollen grains are generally spherical, about 25-50 micrometres across, with a two-layered wall:

Exine: hard outer layer of sporopollenin, one of the most resistant organic materials known. It withstands high temperature and strong acids and alkalis, and no known enzyme breaks it down (which is why pollen survives as fossils). It has gaps called germ pores where sporopollenin is absent; the pollen tube comes out through one of them.
Intine: thin, continuous inner layer of cellulose and pectin.

Inside the plasma membrane, a mature pollen grain has two cells:

Vegetative cell: bigger, with abundant food reserve and a large, irregularly shaped nucleus.
Generative cell: small, spindle-shaped, with dense cytoplasm and a nucleus; it floats in the cytoplasm of the vegetative cell.

In over 60 per cent of angiosperms pollen is shed at this two-celled stage. In the rest, the generative cell divides by mitosis before shedding to give two male gametes (the three-celled stage). In two-celled pollen this division happens later, inside the pollen tube.

Pollen and people. Pollen of many plants (Parthenium or carrot grass, which reached India as a contaminant of imported wheat, is one) causes allergies and bronchial problems such as asthma. Pollen is rich in nutrients and is sold as a food supplement. Viability varies: in rice and wheat pollen loses viability within about 30 minutes of release, while in some members of Rosaceae, Leguminosae and Solanaceae it stays viable for months. Pollen can be stored for years in liquid nitrogen at -196 °C (pollen banks), which helps plant breeders.

Draw and label 1: T.S. of a young anther (or one microsporangium enlarged). Checklist: four-lobed outline with connective in the middle; in one sporangium show the four wall layers in order and a central mass. Labels: epidermis, endothecium, middle layers, tapetum, sporogenous tissue (or microspore mother cells), connective.

Draw and label 2: mature pollen grain. Checklist: circle with a thick, sculptured outer wall broken by a germ pore, a thin inner wall, one large nucleus and a small spindle-shaped cell. Labels: exine, intine, germ pore, vegetative cell (with its nucleus), generative cell. For a three-celled pollen grain, replace the generative cell with two male gametes.

Microsporogenesis and the Pollen Grain: key facts

Pollen grains from PMCs: $pollen grains = 4 \times number of PMCs$; One meiosis per PMC gives a tetrad of 4 microspores, each becoming one pollen grain.
Meiotic divisions for N pollen grains: $meioses = \frac{N}{4}$; Mitosis inside the pollen grain does not add meioses.
Ploidy along the male line: $PMC (2 n) \to microspore (n) \to vegetative, generative cells, male gametes (n)$; Anther wall layers, including the tapetum, are diploid sporophyte tissue.
Wall layers, outside in: $epidermis \to endothecium \to middle layers \to tapetum$; Tapetum nourishes; the outer three protect and help dehiscence.
Two-celled vs three-celled pollen: $generative cell mitosis 2 male gametes$; Before shedding: three-celled pollen; after shedding, in the pollen tube: two-celled pollen (over 60% of angiosperms).

How to answer Microsporogenesis and the Pollen Grain questions

Questions on this topic ask you to describe, draw, give a function or count. Use the pattern that fits.

1Describe microsporogenesis in sequence: sporogenous tissue → PMC (2n) → meiosis → tetrad → microspores → pollen grains. Name meiosis explicitly; it carries the mark.
2For the wall layers, list them outside to inside and pair each with its role: outer three protect and help dehiscence; tapetum nourishes.
3For 'development of the male gametophyte', start from the microspore: it enlarges, forms a vacuole, its nucleus divides by mitosis into a vegetative and a generative cell; the generative cell later divides by mitosis into two male gametes.
4For counting questions, write the rule first (1 PMC → 1 meiosis → 4 pollen), then substitute; for seeds, add meioses on the female side (1 per ovule).
5For ploidy questions, ask whether the cell is sporophyte tissue (2n: wall layers, PMC) or gametophyte (n: microspore, pollen cells, gametes).
6Draw with a sharp pencil, label on one side with straight lines, and give the diagram a title.

Microsporogenesis and the Pollen Grain in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Pollen counting from meiosis

Suppose a plant breeder needs at least 10,000 pollen grains of a mango variety for a hand-pollination programme and estimates that one anther holds about 600 pollen mother cells, of which 10 per cent fail to complete meiosis.

How many pollen grains does one anther give, and how many anthers must she collect to have at least 10,000 grains?

Try it first, then show the solutionSolution

PMCs that complete meiosis = 600 × 0.9 = 540.
Each completed meiosis gives a tetrad: pollen per anther = 540 × 4 = 2160.
Anthers needed = 10,000 ÷ 2160 = 4.63, so round up to 5 anthers (5 × 2160 = 10,800 grains).

Answer: About 2160 pollen grains per anther; she must collect 5 anthers.

Memory hook: One mother cell, one meiosis, four pollen.

Tricks to remember Microsporogenesis and the Pollen Grain

Short memory aids. Say each one aloud once, then use it on a question the same day.

Every Elephant Must Tiptoe
Epidermis, Endothecium, Middle layers, Tapetum: outermost to innermost.
Use it when: Labelling the microsporangium wall in order.
Ex is tough, In is soft
EXine = EXtra tough sporopollenin; INtine = INner cellulose-pectin.
Use it when: Matching the pollen wall layers to their chemistry.
Tapetum = tiffin
The tapetum packs the tiffin for growing pollen.
Use it when: Recalling the nourishing function of the tapetum.

Microsporogenesis and the Pollen Grain: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Sporogenous tissue vs tapetum · 2 marks · Very short answerBoard level

Distinguish between the sporogenous tissue and the tapetum of a young microsporangium on the basis of position, nature of cells and fate.

Try it first, then show the solutionSolution

Sporogenous tissue: occupies the centre of the microsporangium; compactly arranged, similar-looking (homogeneous) cells; each cell can act as a pollen mother cell and undergo meiosis to form a microspore tetrad (1 mark).
Tapetum: innermost wall layer, surrounding the sporogenous tissue; cells with dense cytoplasm and generally more than one nucleus; it nourishes the developing pollen grains (1 mark).

Answer: Sporogenous tissue: central, homogeneous cells that become PMCs and form microspores. Tapetum: innermost wall layer with dense, often multinucleate cells that nourish the pollen.

Example 2: Counting pollen grains · 1 mark · Very short answerBoard level

An anther has 4 microsporangia, and each microsporangium has 80 pollen mother cells. How many pollen grains will the anther produce, and how many meiotic divisions are needed?

Try it first, then show the solutionSolution

PMCs = 4 × 80 = 320; each undergoes one meiosis, so 320 meioses.
Each meiosis gives 4 microspores: 320 × 4 = 1280 pollen grains.

Answer: 1280 pollen grains from 320 meiotic divisions.

Example 3: Development of the male gametophyte · 5 marks · Long answerHarder board level

Describe the development of the male gametophyte from a pollen mother cell in an angiosperm. Draw a labelled diagram of a three-celled mature pollen grain. (A question of this kind was asked in 2024.)

Try it first, then show the solutionSolution

The diploid PMC in the microsporangium undergoes meiosis to form a microspore tetrad of four haploid cells (1 mark).
As the anther matures and dehydrates, the microspores separate; each enlarges and its nucleus divides by mitosis into a large vegetative cell (food reserve, big irregular nucleus) and a small, spindle-shaped generative cell floating in its cytoplasm (1 mark).
The wall develops a sporopollenin exine with germ pores and a cellulose-pectin intine (½ mark). In three-celled pollen, the generative cell divides by mitosis into two male gametes before shedding; in two-celled pollen this happens in the pollen tube (1 mark).
Diagram: exine, intine, germ pore, vegetative cell nucleus, two male gametes, with a title (1½ marks).

Answer: PMC (2n) → meiosis → tetrad → microspore → mitosis → vegetative + generative cell → mitosis of generative cell → 2 male gametes; diagram labelled as above.

Example 4: Why fossil pollen survives · 2 marks · Very short answerHarder board level

Pollen grains are well preserved as fossils. Give the reason and also explain how the pollen tube can still emerge through such a resistant wall.

Try it first, then show the solutionSolution

The exine is made of sporopollenin, which resists high temperature, strong acids and alkalis, and no enzyme is known to degrade it, so the wall survives for long periods (1 mark).
Sporopollenin is absent at the germ pores, so the pollen tube grows out through a germ pore (1 mark).

Answer: Sporopollenin exine resists decay; the pollen tube emerges through germ pores where sporopollenin is absent.

Example 5: Ploidy across the anther · 3 marks · Short answerHarder board level

The leaf cells of a plant have 24 chromosomes. Give the number of chromosomes in (a) a tapetum cell nucleus, (b) a pollen mother cell, (c) a microspore, (d) a generative cell, (e) a male gamete. Justify (a).

Try it first, then show the solutionSolution

(a) 24: the tapetum is part of the anther wall, which is sporophyte tissue formed by mitosis (2n) (1 mark).
(b) 24: the PMC is diploid before meiosis. (c) 12: meiosis halves the number (1 mark).
(d) 12 and (e) 12: the generative cell and male gametes come from the microspore by mitosis, so they stay haploid (1 mark).

Answer: (a) 24 (b) 24 (c) 12 (d) 12 (e) 12.

Example 6: Meioses behind seeds · 3 marks · Short answerHOTS / competency

Each seed of a plant comes from one ovule, which forms from one megaspore mother cell (one meiosis, one functional megaspore), and one pollen grain. How many meiotic divisions are needed in all to produce 480 seeds?

Try it first, then show the solutionSolution

Female side: one meiosis per ovule, so 480 meioses (1 mark).
Male side: one meiosis gives 4 pollen grains, so 480 ÷ 4 = 120 meioses (1 mark).
Total = 480 + 120 = 600 meiotic divisions (1 mark).

Answer: 600 meiotic divisions (480 female + 120 male).

Where students lose marks in Microsporogenesis and the Pollen Grain

The slips examiners see most often, and what to write instead.

Mistake: Wrong order of wall layers
Students mix up endothecium and tapetum.
Wrong working
Epidermis, tapetum, middle layers, endothecium.
Right working
Epidermis, endothecium, middle layers, tapetum.
Do this: Tapetum is always innermost, next to the sporogenous tissue.
Usually costs: 1 mark on labelling.
Mistake: Saying pollen is diploid or that male gametes form by meiosis
Students think every gamete-forming division is meiosis.
Wrong working
The generative cell undergoes meiosis to form two male gametes.
Right working
The generative cell divides by mitosis; meiosis occurred earlier, in the PMC.
Do this: In plants, meiosis forms spores; gametes form from the gametophyte by mitosis.
Usually costs: 1-2 marks in development questions.
Mistake: Writing that intine is made of sporopollenin
Exine and intine are swapped.
Wrong working
Intine is made of sporopollenin; exine of pectin.
Right working
Exine: sporopollenin. Intine: cellulose and pectin.
Do this: Exine = Extra tough.
Usually costs: 1 mark.
Mistake: Forgetting the female meioses in seed-count questions
Students count only pollen.
Wrong working
Seeds 480 → meioses = 480 ÷ 4 = 120.
Right working
120 (male) + 480 (female) = 600.
Do this: Each seed needs one ovule (one meiosis) and one pollen grain (¼ meiosis).
Usually costs: The 1-mark MCQ.

Exam tips

Use the term 'microspore tetrad' and say 'meiosis' when describing microsporogenesis.
In the pollen diagram, show the germ pore as a gap in the exine only; the intine stays continuous.
When asked for the function of the tapetum, one clear line is enough: it nourishes the developing pollen grains.
Write numerical answers with the rule first: 1 PMC → 1 meiosis → 4 pollen grains.
Mention both two-celled (over 60% of angiosperms) and three-celled stages when describing the mature pollen grain.

Practice questions on Microsporogenesis and the Pollen Grain

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
The innermost wall layer of a microsporangium, whose cells have dense cytoplasm and often more than one nucleus, is the:
(a) endothecium (b) middle layer (c) tapetum (d) epidermis
Hint
Think of the layer that feeds the pollen.
Answer
(c) tapetum.
Q2 · 1 mark · Assertion-reasonBoard level
Assertion (A): The exine of a pollen grain has germ pores.
Reason (R): Sporopollenin is absent at the germ pores.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Hint
What is a germ pore made of, or not made of?
Answer
(a). Germ pores are exactly the places where the exine lacks sporopollenin.
Q3 · 1 mark · Very short answerBoard level
How many pollen grains and how many microspore tetrads are formed from 125 pollen mother cells?
Hint
One PMC gives one tetrad.
Answer
125 tetrads and 500 pollen grains.
Q4 · 3 marks · Short answerHarder board level
Differentiate between the vegetative cell and the generative cell of a pollen grain on three points.
Hint
Size, shape of nucleus, food reserve, fate.
Answer
Vegetative cell: bigger; abundant food reserve; large irregularly shaped nucleus; forms the pollen tube. Generative cell: small, spindle-shaped; dense cytoplasm; floats in the vegetative cell's cytoplasm; divides by mitosis into two male gametes.
Q5 · 1 mark · Assertion-reasonHarder board level
Assertion (A): Tapetal cells are often multinucleate.
Reason (R): Tapetal cells undergo meiosis without cytokinesis.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Hint
Tapetum is wall tissue, not a spore-forming cell.
Answer
(c). Tapetal cells are often multinucleate, but because nuclei divide without the cell dividing (not by meiosis); meiosis happens in the PMCs, not the tapetum.
Q6 · 3 marks · Short answerHOTS / competency
Suppose a seed company wants to cross a wheat variety that flowers in Punjab with a wild relative that flowers six weeks later in another state. (a) Why can it not simply carry fresh pollen across in a box? (b) What should it do instead, and why does this work?
Hint
Viability of wheat pollen; storage temperature.
Answer
(a) Wheat pollen loses viability within about 30 minutes of release, so fresh pollen will be dead long before use (1 mark). (b) Collect pollen and store it in liquid nitrogen at -196 °C (a pollen bank), then thaw and use it when the wild relative flowers (1 mark); at this temperature metabolism practically stops, so viability is kept for years (1 mark).
Q7 · 4 marks · Case-basedHarder board level
Read and answer.
Suppose a student examines a transverse section of a young anther and a few days later a section of a mature anther of the same flower. In the young anther, the centre of each sporangium has a mass of compact cells and the innermost wall layer is thick with dense cytoplasm. In the mature anther, the sporangium is full of loose, separate grains and the innermost wall layer has almost disappeared.
(a) Name the central compact tissue of the young anther. (1)
(b) Which process converted it into loose grains, and what kind of cell division does it involve? (1)
(c) Why does the innermost layer shrink as the anther matures? Explain. (2)
Hint
The innermost layer is the tapetum; what was it doing?
Answer
(a) Sporogenous tissue (pollen mother cells). (b) Microsporogenesis, involving meiosis of each PMC to form tetrads that then separate. (c) The tapetum nourishes the developing pollen grains; its contents are used up as the pollen matures, so it degenerates by the time the pollen is ready.
Q8 · 2 marks · Very short answerHarder board level
Explain why the pollen grain is called the male gametophyte, and name the cells that make it gametophytic rather than sporophytic.
Hint
A gametophyte is haploid and forms gametes.
Answer
The pollen grain develops from a haploid microspore and itself produces the male gametes (from the generative cell by mitosis), so it is the haploid gamete-forming generation. Its vegetative and generative cells are haploid.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.How many microsporangia does a typical anther have?Show answer
Four, two in each lobe.
2.Which wall layer nourishes pollen?Show answer
Tapetum.
3.What is the exine made of?Show answer
Sporopollenin.
4.What is the intine made of?Show answer
Cellulose and pectin.
5.How many pollen grains do 50 PMCs give?Show answer
200.
6.At what temperature are pollen grains stored in pollen banks?Show answer
-196 °C, in liquid nitrogen.

Microsporogenesis and the Pollen Grain: frequently asked questions

What is microsporogenesis?

The formation of haploid microspores from a diploid pollen mother cell by meiosis inside the microsporangium of an anther. Each PMC gives a tetrad of four microspores.

What is the function of the tapetum?

The tapetum, the innermost wall layer of the microsporangium, nourishes the developing pollen grains.

Why is sporopollenin important?

It makes the exine resistant to high temperature, strong acids, alkalis and enzymes, so pollen survives harsh conditions and is preserved as fossils.

What is the difference between two-celled and three-celled pollen?

Two-celled pollen is shed with a vegetative and a generative cell; the generative cell divides in the pollen tube. Three-celled pollen is shed after the generative cell has already divided into two male gametes.

Is microsporogenesis the same as the formation of the male gametophyte?

No. Microsporogenesis ends with microspores. Development of the male gametophyte starts from the microspore and includes the mitoses that form the vegetative cell, generative cell and male gametes.