BiologyISC Class 12 · Sexual Reproduction in Flowering Plants

Microsporogenesis and Pollen Grain: ISC Class 12 Biology

Updated 15 October 2026 · Fact-checked

Microsporogenesis is the formation of haploid microspores from a diploid pollen mother cell by meiosis inside the microsporangium of an anther. Each microspore develops into a pollen grain, the male gametophyte, with a sporopollenin exine, a cellulose-pectin intine, and a vegetative cell and generative cell.

Understand Microsporogenesis and Pollen Grain

The anther. A stamen has a slender filament and a terminal anther. A typical angiosperm anther is bilobed and each lobe has two thecae, so it is dithecous. In transverse section it looks four-cornered (tetragonal) with four microsporangia, two per lobe, which later become pollen sacs. The lobes are joined by the connective, which carries a vascular strand.

Development of the microsporangium (ISC adds this). In a young anther a mass of uniform meristematic cells is covered by the epidermis. At each of the four corners a hypodermal archesporial cell (archesporial initial) differentiates and divides periclinally into:

an outer primary parietal layer, which divides further to form the wall layers (endothecium, middle layers, tapetum); and
an inner primary sporogenous cell, which forms the sporogenous tissue in the centre of the microsporangium.

Wall layers of a microsporangium (outside → in):
1. Epidermis: single protective layer.
2. Endothecium: cells with fibrous thickenings; helps the anther to dehisce.
3. Middle layers: 2-3 layers, usually crushed and degenerate at maturity.
4. Tapetum: innermost; cells with dense cytoplasm, often with more than one nucleus; nourishes the developing pollen grains and contributes material for the pollen wall.
The outer three layers protect and help in dehiscence; the tapetum feeds.

Microsporogenesis. Each cell of the sporogenous tissue is a potential pollen mother cell (PMC) or microspore mother cell (2n). Each PMC divides by meiosis into four haploid microspores held together as a microspore tetrad. As the anther matures and dries, the microspores separate. Thousands of pollen grains form in each microsporangium and are released when the anther dehisces along the line of dehiscence (stomium).

Flow chart: archesporial cell → primary sporogenous cell → sporogenous tissue → pollen mother cell (2n) → meiosis → microspore tetrad (n) → microspores → pollen grains.

Pollen grain (male gametophyte).

Usually spherical, about 25-50 µm across.
Exine: hard outer layer of sporopollenin, one of the most resistant organic substances known; it withstands high temperature and strong acids and alkalis, and no enzyme is known that breaks it down. This is why pollen survives as fossils. Exine shows species-specific patterns and has germ pores where sporopollenin is absent; the pollen tube emerges through a germ pore.
Intine: thin, continuous inner layer of cellulose and pectin.
Development: the microspore nucleus divides by mitosis into a large vegetative cell (abundant food reserve, large irregular nucleus) and a small spindle-shaped generative cell floating in its cytoplasm. In over 60% of angiosperms pollen is shed at this two-celled stage; in the rest the generative cell divides by mitosis into two male gametes before shedding (three-celled stage). In two-celled pollen the generative cell divides inside the pollen tube.

Viability. The period during which pollen can germinate after release. It depends on species, temperature and humidity: about 30 minutes in rice and wheat; months in some members of Rosaceae, Leguminosae and Solanaceae. Pollen of many species can be stored for years in liquid nitrogen at −196 °C in pollen banks for crop breeding.

Economic importance. Pollen tablets and syrups are sold as food supplements (claimed to improve the performance of athletes and race horses). Pollen of some plants causes allergies, asthma and bronchitis; Parthenium (carrot grass), which entered India as a contaminant of imported wheat, is a major cause of pollen allergy. Pollen banks support plant breeding; fossil pollen (thanks to sporopollenin) records past vegetation.

Draw and label: T.S. of a mature anther. Checklist: bilobed outline with four rounded pollen sacs; connective with a vascular strand in the middle; label epidermis, endothecium, middle layers, tapetum (around a young sac), pollen grains inside, line of dehiscence between two sacs of a lobe. Draw a T.S., not an L.S., and not a testis.

Draw and label: pollen grain. Checklist: thick outer exine with a gap (germ pore), thin inner intine, plasma membrane, vegetative cell with large irregular nucleus, small spindle-shaped generative cell.

Microsporogenesis and Pollen Grain: key facts

Pollen grains from mother cells: $pollen grains = 4 \times pollen mother cells = 4 \times meiotic divisions$; Every microspore of a tetrad becomes a pollen grain.
Anther arithmetic: $pollen per anther = 4 microsporangia \times PMCs per microsporangium \times 4$; Tetrasporangiate anther.
Ploidy: $PMC (2 n) meiosis 4 microspores (n) mitosis vegetative + generative (n)$; Generative cell → 2 male gametes (n) by one more mitosis.
Wall layers: $epidermis \to endothecium \to middle layers \to tapetum$; Outside to inside; tapetum nourishes.

How to answer Microsporogenesis and Pollen Grain questions

Expect a labelled T.S. of anther, identification of a cell in a developmental diagram, short answers on exine and tapetum, and simple counting of pollen grains or meioses.

1For a developmental diagram, place the cell: hypodermal cell at a corner of a young anther = archesporial cell; its outer derivative = primary parietal layer; inner = primary sporogenous cell.
2For wall-layer questions, give the order outside to inside and the function of each: protection, dehiscence, nourishment.
3For counting, remember one meiosis gives four pollen grains, but one megaspore mother cell gives only one functional megaspore.
4For ploidy, everything after meiosis (microspore, vegetative cell, generative cell, male gametes) is haploid; anther wall cells are diploid.
5For 'why' questions on pollen, link exine to sporopollenin (resistance, fossils) and germ pores to pollen tube emergence.
6For viability, quote the contrast: 30 minutes (rice, wheat) versus months (Rosaceae, Leguminosae, Solanaceae), and storage at −196 °C.

Microsporogenesis and 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 viability and pollen banks

Suppose a rice breeder wants to cross a variety grown in Odisha, which flowers about two weeks earlier, with a variety grown in Punjab. She plans to collect pollen from the Odisha plants and carry it by train for a day and a half to the Punjab field.

Will the plan work? Suggest how the breeder could make the cross possible.

Try it first, then show the solutionSolution

Rice pollen loses viability within about 30 minutes of release, so pollen carried for a day and a half at room temperature would be dead.
Viability depends on temperature and humidity; very low temperature stops metabolism.
Pollen can be collected and stored in liquid nitrogen at −196 °C, where it stays viable for long periods.
Stored pollen (a pollen bank) can be thawed and dusted on the emasculated, bagged flowers of the Punjab variety when they bloom two weeks later.

Answer: No: rice pollen survives only about 30 minutes. Cryopreserve the pollen in liquid nitrogen (−196 °C) and use it when the female parent flowers.

Memory hook: Rice pollen is a half-hour visitor; liquid nitrogen makes it a long-term guest.

Tricks to remember Microsporogenesis and Pollen Grain

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

E-E-M-T: outside in
Every Elephant Must Tiptoe: Epidermis, Endothecium, Middle layers, Tapetum.
Use it when: Writing or labelling the wall layers in order.
Tapetum = tiffin
The tapetum packs the tiffin (food) for the young pollen.
Use it when: Function of the tapetum.
Sporopollenin is pollen's armour
Heat, acid, alkali and enzyme cannot break the armour, so pollen fossils survive.
Use it when: Why exine is hard and why pollen fossilises.

Microsporogenesis and Pollen Grain: solved examples

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

Example 1: Archesporial cell · 2 marks · Short answerBoard level

In a young anther, a hypodermal cell at each corner divides periclinally. Name this cell and the two cells it forms, and state what each forms.

Try it first, then show the solutionSolution

The cell is the archesporial cell (archesporial initial) (½ mark).
Outer primary parietal layer → wall layers (endothecium, middle layers, tapetum) (¾ mark).
Inner primary sporogenous cell → sporogenous tissue → pollen mother cells (¾ mark).

Answer: Archesporial cell → primary parietal layer (wall layers) + primary sporogenous cell (sporogenous tissue, PMCs).

Example 2: Wall layers and their jobs · 2 marks · Short answerBoard level

Name the wall layers of a microsporangium from outside inwards and give the function of the outer three together and of the innermost.

Try it first, then show the solutionSolution

Epidermis, endothecium, middle layers, tapetum (1 mark).
Outer three: protection and help in dehiscence to release pollen; tapetum: nourishes the developing pollen grains (1 mark).

Answer: Epidermis, endothecium, middle layers (protection, dehiscence); tapetum (nourishment).

Example 3: Counting pollen · 2 marks · Short answerHarder board level

A flower has 6 stamens. Each anther is tetrasporangiate and releases 2400 pollen grains. (a) How many pollen mother cells were present in each microsporangium? (b) How many meiotic divisions produced all the pollen of the flower?

Try it first, then show the solutionSolution

Each anther: 2400 ÷ 4 = 600 PMCs (one meiosis gives four pollen grains); per microsporangium 600 ÷ 4 = 150 (1 mark).
Flower: 6 × 600 = 3600 meiotic divisions (14 400 pollen grains) (1 mark).

Answer: (a) 150 PMCs per microsporangium. (b) 3600 meiotic divisions.

Example 4: Two-celled and three-celled pollen · 3 marks · Short answerHarder board level

Describe the development of a microspore into a mature pollen grain. What is the difference between pollen shed at the two-celled and three-celled stages, and when does the generative cell divide in each?

Try it first, then show the solutionSolution

The microspore nucleus divides by mitosis (unequal) into a large vegetative cell with food reserves and a large irregular nucleus, and a small spindle-shaped generative cell floating in the vegetative cytoplasm (1 mark).
Two-celled (over 60% of angiosperms): shed as vegetative + generative cell; the generative cell divides into two male gametes inside the pollen tube (1 mark).
Three-celled: the generative cell divides before shedding, so the grain is released with a vegetative cell and two male gametes (1 mark).

Answer: Microspore → vegetative + generative cell; generative cell divides in the tube (two-celled) or before shedding (three-celled).

Example 5: Why fossil pollen tells history · 3 marks · Short answerHarder board level

Pollen grains in a 5000-year-old lake sediment can still be identified to the plant family. Explain which feature of the pollen wall makes this possible, and why the germ pores look different from the rest of the wall.

Try it first, then show the solutionSolution

The exine is made of sporopollenin, which resists high temperature, strong acids and alkalis, and no known enzyme degrades it, so the wall survives decay (1 mark).
The exine carries species-specific patterns, so the family can be identified (1 mark).
Germ pores are apertures where sporopollenin is absent; they are thin so that the pollen tube can emerge there (1 mark).

Answer: Sporopollenin in the exine resists decay and carries identifying patterns; germ pores lack sporopollenin to let the tube out.

Example 6: Tracking the ploidy · 4 marks · Short answerHOTS / competency

Suppose a plant has 2n = 24. Give the chromosome number in (a) a pollen mother cell, (b) a microspore, (c) the generative cell, (d) an endothecium cell. If meiosis failed in a pollen mother cell and its products still developed, what would be the chromosome number of the resulting male gametes, and what would happen to the endosperm ploidy after normal pollination of a diploid flower by them?

Try it first, then show the solutionSolution

(a) 24 (diploid sporogenous derivative) (½ mark). (b) 12 (½ mark). (c) 12 (½ mark). (d) 24 (anther wall is somatic) (½ mark).
If meiosis fails, the products stay diploid, so the male gametes carry 24 chromosomes (1 mark).
Endosperm = two polar nuclei (12 + 12) + male gamete (24) = 48, i.e. tetraploid instead of triploid (1 mark).

Answer: (a) 24 (b) 12 (c) 12 (d) 24; unreduced gametes have 24, giving a 48-chromosome (4n) endosperm.

Where students lose marks in Microsporogenesis and Pollen Grain

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

Mistake: Drawing L.S. of anther or a testis
In 2024 examiners reported that many candidates drew an L.S. of the anther, or even a testis with seminiferous tubules and Leydig cells, when a T.S. of anther was asked.
Do this: T.S. of anther: bilobed, four sacs, connective in the middle; label at least five parts with arrows that do not cross.
Usually costs: Up to 3 marks.
Mistake: Writing 'archegonial' for archesporial
Examiners (2024) noted 'archegonial initial' and names such as tapetum, endothecium or Leydig cells for the hypodermal cell that divides periclinally.
Wrong working
Archegonial initial.
Right working
Archesporial initial (archesporial cell).
Do this: Archegonium belongs to bryophytes and pteridophytes; the anther has an archesporium.
Usually costs: 1 mark.
Mistake: Saying the tapetum protects
Students lump all four wall layers together.
Do this: Outer three layers protect and help dehiscence; the tapetum nourishes.
Usually costs: ½ to 1 mark.
Mistake: Calling pollen the male gamete
Pollen grain and male gamete are used loosely.
Wrong working
Pollen grains are the male gametes of plants.
Right working
The pollen grain is the male gametophyte; it produces two male gametes.
Do this: Gametophyte (pollen) makes gametes (sperm cells).
Usually costs: 1 mark in MCQs and definitions.

Exam tips

Learn the T.S. of anther as a labelled diagram; ISC asks it as a 3-mark drawing.
Use the exact terms: archesporial cell, primary parietal layer, primary sporogenous cell, pollen mother cell.
Give the numbers: 25-50 µm pollen, over 60% shed two-celled, 30 minutes rice and wheat, −196 °C.
Mention sporopollenin whenever you explain fossil pollen or the hardness of the exine.
In counting problems, show the factor of four for each meiosis.

Practice questions on Microsporogenesis and 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 that nourishes the developing pollen is the:
(a) endothecium (b) tapetum (c) middle layer (d) epidermis
Hint
Dense cytoplasm, often more than one nucleus.
Answer
(b) Tapetum.
Q2 · 1 mark · Very short answerBoard level
Name the substance of the exine and of the intine of a pollen grain.
Hint
One is extremely resistant.
Answer
Exine: sporopollenin. Intine: cellulose and pectin.
Q3 · 2 marks · Short answerHarder board level
Arrange in developmental order: microspore tetrad, archesporial cell, pollen grain, primary sporogenous cell, pollen mother cell, male gametes.
Hint
Start below the epidermis of a young anther.
Answer
Archesporial cell → primary sporogenous cell → pollen mother cell → microspore tetrad → pollen grain → male gametes.
Q4 · 1 mark · Assertion-reasonHarder board level
Assertion (A): Pollen grains of rice cannot be used for crossing a day after they are shed unless stored specially.
Reason (R): Pollen of rice loses viability within about 30 minutes of release.
(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
Cereal pollen is short-lived.
Answer
(a).
Q5 · 3 marks · Short answerHarder board level
Give three differences between microsporogenesis and megasporogenesis.
Hint
Where, from which mother cell, and how many products survive?
Answer
Site: microsporangium of the anther versus nucellus of the ovule. Mother cell: many pollen mother cells from the sporogenous tissue versus usually a single megaspore mother cell near the micropylar end. Products: all four microspores of a tetrad become pollen grains, whereas of the four megaspores usually only one is functional and three degenerate.
Q6 · 3 marks · Short answerHarder board level
Why is the anther called dithecous and tetrasporangiate? Draw a labelled T.S. of a mature anther showing at least five parts.
Hint
Lobes, thecae, sacs; T.S. not L.S.
Answer
Each of the two lobes has two thecae (dithecous), giving four microsporangia in all (tetrasporangiate). Diagram: bilobed outline, four pollen sacs with pollen grains, connective with vascular strand, epidermis, endothecium, middle layers (remnants), tapetum, line of dehiscence.
Q7 · 3 marks · Short answerHOTS / competency
Suppose a gene mutation makes the tapetum of a plant degenerate very early, before the microspores separate from their tetrads. Predict two effects on the pollen and on seed set, giving reasons.
Hint
What does the tapetum supply?
Answer
The tapetum nourishes developing pollen and supplies material for the pollen wall. Without it the microspores would be starved and their walls poorly formed, so the pollen would be shrivelled or non-viable (male sterility). Few or no viable pollen grains would reach stigmas, so seed set after self-pollination would fail; the plant could still set seed if pollen from normal plants reached it (useful to breeders as a male-sterile line).
Q8 · 3 marks · Case-basedHOTS / competency
Read and answer.
Suppose a city hospital records a rise in asthma cases every year when a weed with small white flowers spreads along roadsides. A botanist identifies it as a plant that came into India as a contaminant of imported wheat.
(a) Name the weed. (1)
(b) Which part of the plant triggers the attacks, and through which organs does it enter the body? (1)
(c) Give one beneficial use of pollen to humans. (1)
Hint
Carrot grass.
Answer
(a) Parthenium (carrot grass). (b) Its pollen grains, inhaled through the nose and airways, cause allergy, asthma and bronchitis. (c) Pollen tablets or syrups as food supplements; pollen banks for crop breeding (either).

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.What type of division forms microspores?Show answer
Meiosis of the pollen mother cell.
2.Where is sporopollenin absent in the exine?Show answer
At the germ pores.
3.Which cell of the pollen grain forms the male gametes?Show answer
The generative cell.
4.Which layer helps dehiscence through fibrous thickenings?Show answer
Endothecium.
5.At what temperature is pollen stored in pollen banks?Show answer
−196 °C, in liquid nitrogen.
6.Name a weed whose pollen causes allergy in India.Show answer
Parthenium (carrot grass).

Microsporogenesis and 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.

What is the function of the tapetum?

It nourishes the developing pollen grains and supplies material for the pollen wall.

Why is the exine so resistant?

It is made of sporopollenin, which withstands high temperature, strong acids and alkalis; no enzyme is known to degrade it.

What is pollen viability?

The period for which pollen can germinate after release; it ranges from about 30 minutes in rice and wheat to months in some Rosaceae, Leguminosae and Solanaceae.

Is the pollen grain the male gamete?

No. It is the male gametophyte; its generative cell divides to form two male gametes.