Sexual Reproduction IN Flowering Plant flash cards

1. 1.What is the reproductive unit in flowering plants (angiosperms)?

   The flower.

   Hint: Sexual reproduction structure

2. 2.Name the four whorls of a typical flower.

   Calyx (sepals), Corolla (petals), Androecium (stamens), Gynoecium (carpels/pistils).

   Hint: Outer to inner

3. 3.Which whorls are the essential (reproductive) whorls of a flower?

   Androecium (male) and Gynoecium (female).

   Hint: The other two are accessory

4. 4.What are the parts of a typical stamen?

   A long, slender filament and a terminal, usually bilobed anther.

   Hint: Male reproductive unit

5. 5.How many pollen sacs (microsporangia) does a typical dithecous anther have?

   Four microsporangia — two in each of the two lobes (bilobed, dithecous).

   Hint: Tetrasporangiate

6. 6.Name the four wall layers of a microsporangium from outside to inside.

   Epidermis, Endothecium, Middle layers, and Tapetum.

   Hint: Three protective + one nourishing

7. 7.Which anther wall layer nourishes the developing pollen grains?

   The tapetum (innermost layer); its cells are dense with cytoplasm and often multinucleate.

   Hint: Innermost, nutritive

8. 8.What tissue occupies the centre of a young anther and gives rise to microspores?

   The sporogenous tissue (compactly arranged homogeneous cells).

   Hint: Becomes microspore mother cells

9. 9.What is microsporogenesis?

   The process of formation of microspores from a pollen mother cell (microspore mother cell) through meiosis.

   Hint: Meiosis → microspore tetrads

10. 10.By what type of division do microspore mother cells form microspores?

    Meiosis (reductional division).

    Hint: Diploid → haploid

11. 11.What is a microspore tetrad?

    A cluster of four haploid microspores produced from one microspore mother cell after meiosis.

    Hint: Usually arranged in a group of four

12. 12.What does each microspore develop into?

    A pollen grain.

    Hint: Male gametophyte

13. 13.The pollen grain represents which generation/gametophyte?

    The male gametophyte.

    Hint: Haploid, from microspore

14. 14.Name the two layers of the pollen grain wall.

    Outer exine (hard, made of sporopollenin) and inner intine (thin, of cellulose and pectin).

    Hint: Exine tough, intine soft

15. 15.What is exine of the pollen wall made of, and why is it significant?

    Made of sporopollenin — one of the most resistant organic materials; it resists high temperature, strong acids and alkali, so pollen is well preserved as fossils.

    Hint: No enzyme can degrade it

16. 16.What are germ pores?

    Regions of the pollen wall where the exine is absent; the pollen tube emerges through them.

    Hint: Gaps in sporopollenin

17. 17.Describe the cells present in a mature pollen grain in about 60% of angiosperms (at shedding, 2-celled stage).

    A large vegetative cell (with abundant food reserve and irregular nucleus) and a small generative cell (spindle-shaped, floating in vegetative cell cytoplasm).

    Hint: Vegetative + generative

18. 18.At what cell stage are pollen grains shed in about 60% of angiosperms?

    At the 2-celled stage (vegetative cell + generative cell).

    Hint: Others shed at 3-celled

19. 19.In the remaining ~40% of species, the generative cell divides to form what before pollen is shed?

    Two male gametes — so pollen is shed at the 3-celled stage.

    Hint: Generative cell → 2 sperms

20. 20.Pollen grains of some species cause what human health problem?

    Allergies and respiratory disorders (e.g., pollen allergy, asthma, bronchitis); e.g., Parthenium/carrot grass.

    Hint: Allergen

21. 21.For how long do pollen grains remain viable in cereals like rice and wheat?

    About 30 minutes only (short viability).

    Hint: Very short-lived

22. 22.In which families can pollen remain viable for months?

    Rosaceae, Leguminosae and Solanaceae — viable for months.

    Hint: Long viability

23. 23.How are pollen grains stored for years for crop breeding, and by what method?

    By cryopreservation — stored in liquid nitrogen at $-196^{\circ}C$, forming pollen banks.

    Hint: Liquid nitrogen

24. 24.What are the three parts of a pistil (carpel)?

    Stigma, style and ovary.

    Hint: Top to bottom

25. 25.What is the function of the stigma?

    It is the receptive surface (landing platform) for pollen grains.

    Hint: Where pollen lands

26. 26.Where are the ovules (megasporangia) located in the pistil?

    Inside the ovary, attached to the placenta.

    Hint: Enlarged basal part

27. 27.What is the placenta in the ovary?

    The cushion-like tissue to which ovules are attached inside the ovary.

    Hint: Ovule attachment site

28. 28.What is the funicle?

    The stalk by which the ovule is attached to the placenta.

    Hint: Ovule stalk

29. 29.What is the hilum?

    The junction/point where the body of the ovule fuses with the funicle.

    Hint: Funicle-ovule junction

30. 30.What are integuments of the ovule?

    Protective envelopes (one or two layers) that surround the nucellus, leaving a small opening.

    Hint: Protective coats

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