Sexual Reproduction in Flowering Plants – Quick Revision

Life Cycle of Plants

  • Sequence: seed germination → juvenile/vegetative phase → reproductive phase → senescent phase → death.
  • Juvenile/vegetative: growth of root, stem, leaf; active cell division & elongation; no flowering.
  • Reproductive: flowering, gamete formation, fertilization, seed production.
  • Senescent: metabolic decline, yellowing leaves, organism dies.

Types of Reproduction

  • Asexual (no gamete fusion)
    • Vegetative: runner, offset, stolon, sucker, tuber.
    • Other modes: fission, budding, fragmentation, regeneration, gemmae.
  • Sexual
    • Meiosis → haploid gametes (n)(n).
    • Gamete fusion → zygote (2n)(2n) → embryo → seed (end-product of sexual reproduction).

Sexual Reproduction in Angiosperms

  • Angiosperms = “covered seeds”.
    • Monocots (1 cotyledon): wheat, rice, maize.
    • Dicots (2 cotyledons): pea, bean, urad.
  • Post-fertilisation changes
    • Ovule → seed.
    • Integuments → seed coat.
    • Ovary → fruit.
    • Ovary wall → pericarp (fruit wall).
  • Dominant phase of angiosperm plant body = sporophyte (2n)(2n).

Floral Structure – Quick Facts

  • Four concentric whorls:
    1. Calyx (sepals) – outermost.
    2. Corolla (petals).
    3. Androecium (stamens).
    4. Gynoecium (carpels).
  • Unisexual flower lacks either androecium OR gynoecium (never both).
  • Fruit originates from the ovary after fertilisation.

Plant Categories & Generations

  • Vascular, diploid sporophyte dominant: pteridophytes, gymnosperms, angiosperms.
  • Non-vascular: algae & fungi; bryophytes are non-vascular but have dominant haploid gametophyte.

Life-Span Terminology

  • Annual: completes full life cycle within ≤1\le 1 year; flowers once (e.g., wheat, rice).
  • Biennial: two-year cycle; 1st year vegetative, 2nd year flowering/seed (e.g., carrot, radish).
  • Perennial: lives many years, flowers repeatedly (e.g., mango, coconut).
    • Exceptions: bamboo & Neelakuranji – perennial but flower only once.