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Sexual Reproduction in Flowering Plants

Biology · Class 12pp. 1–232 sets × 25 questionsFree

Key facts and formulas for Sexual Reproduction in Flowering Plants, three worked sample questions, and two full practice sets. Every question has a hint, a reason for every option and a step-by-step solution, with a calculator or animation where one helps. English and Hinglish.

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Key facts for this chapter

IdeaRule or fact
AntherDithecous, 4 microsporangia. Wall layers outside in: epidermis, endothecium, middle layers, tapetum (nourishes pollen).
Pollen formation1 PMC (2n) → meiosis → 4 microspores (n) → 4 pollen grains. Pollen has exine (sporopollenin, absent at germ pores) and intine (cellulose, pectin).
Ovule and embryo sacHilum joins body and funicle. Monosporic embryo sac: 1 → 2 → 4 → 8 nuclei by 3 mitoses. Egg apparatus = egg + 2 synergids; antipodals at chalazal end.
Kinds of pollinationAutogamy (same flower), geitonogamy (same plant), xenogamy (different plants). Cleistogamy: closed flowers, assured seed set.
Pollinating agentsWind: light dry pollen, feathery stigma. Water: about 30 genera, mostly monocots. Water lily and hyacinth: insect or wind. Insects: sticky pollen.
Barriers to self-pollinationDichogamy (protandry, protogyny), heterostyly, self-incompatibility (pistil stops self-pollen), dioecy.
Double fertilisationSyngamy: male gamete + egg → zygote (2n). Triple fusion: male gamete + 2 polar nuclei → PEN (3n). Pollen tube: stigma → style → ovary → micropyle → synergid.
Endosperm and seedEndosperm 3n. Types: nuclear, cellular, helobial. Perisperm = leftover nucellus (black pepper, beet). Testa outer, tegmen inner coat.
Grass embryoScutellum is the cotyledon. Coleoptile covers the shoot, coleorhiza covers the radicle.
Fruits and apomixisApple is a false fruit. Banana is parthenocarpic. Mango and coconut are drupes. Apomixis: seeds without fertilisation, offspring are clones of the mother.

Three sample questions

Q1. Which of the following gives the correct order of events in the development of a flower?
  1. Inflorescence → floral primordium → flowers → floral buds
  2. Floral primordium → inflorescence → floral buds → flowers
  3. Floral buds → floral primordium → inflorescence → flowers
  4. Flowers → floral buds → inflorescence → floral primordium
Hint and solution

Hint: Think of the first tiny group of cells that becomes a flower, then the axis that carries many buds, then the open flower.

  1. Floral primordium = first stage — After the plant is ready to flower, hormonal and structural changes form the floral primordium.
  2. Primordium → inflorescence — Floral primordia differentiate into an inflorescence, the axis carrying the flower buds.
  3. Inflorescence → floral buds → flowers — The buds on the inflorescence finally open into flowers.
  4. Answer: primordium → inflorescence → buds → flowers — This is the sequence in option B, so the correct option is B. Option B.
Answer: B. After the plant decides to flower, hormonal and structural changes lead to the floral primordium, which gives inflorescences carrying floral buds, and the buds open as flowers.
Q2. Consider these statements about the anther.
I. A typical anther is dithecous.
II. A transverse section shows four microsporangia.
III. Tapetum is the outermost layer of the microsporangium wall.
Which are correct?
  1. I and III only
  2. II and III only
  3. I, II and III
  4. I and II only
Hint and solution

Hint: Remember where the tapetum sits in the wall: does it protect from outside, or nourish the cells inside?

  1. Typical anther = bilobed, dithecous — Each anther has two lobes with two thecae, so statement I is correct.
  2. T.S. shows 4 microsporangia — Two in each lobe, so statement II is correct.
  3. Wall layers: epidermis → endothecium → middle layers → tapetum — The tapetum is the innermost layer and nourishes developing pollen. So III is wrong.
  4. I and II only — Only I and II are correct, which is option D. Option D.
Answer: D. Tapetum is the innermost wall layer, so III is wrong. I and II are correct.
Q3. From the outside inwards, the layers of the wall of a microsporangium are
  1. epidermis, endothecium, middle layers, tapetum
  2. tapetum, middle layers, endothecium, epidermis
  3. epidermis, middle layers, endothecium, tapetum
  4. endothecium, epidermis, tapetum, middle layers
Hint and solution

Hint: The layer touching the outside is the epidermis, and the layer that feeds the pollen sits deepest, next to the sporogenous tissue.

  1. Wall = 4 layers — The microsporangium wall has four layers: epidermis, endothecium, middle layers and tapetum.
  2. Outermost = epidermis — Epidermis protects the anther, so it is first from outside.
  3. Innermost = tapetum — Tapetum lies next to the sporogenous tissue and nourishes the developing pollen, so it is last.
  4. epidermis → endothecium → middle layers → tapetum — This matches option A. Option A.
Answer: A. The order is epidermis, endothecium, middle layers, tapetum. The tapetum is innermost and nourishes the pollen.

How to use this chapter

Read the NCERT pages first, then attempt Set 1 without the hints. Note every wrong answer in a mistake list, read the reason for each option, and retry Set 2 two days later. A topic is solid when you can say why each wrong option is wrong.

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