CBSE · Class 10 · Science · How do Organisms Reproduce?Explain the process of sexual reproduction in flowering plants with the help of a neat and well-labeled diagram description. Describe the role of different parts of a flower in this process.

Introduction to Sexual Reproduction in Flowering Plants\nSexual reproduction in flowering plants involves the fusion of male and female gametes to form a zygote, which eventually develops into a seed. Flowers are the reproductive organs of angiosperms. A typical flower consists of four main whorls: sepals, petals, stamens, and carpels.

Role of Different Parts of a Flower

• Sepals (Calyx): These are the outermost green, leaf-like structures that protect the flower in the bud stage.
• Petals (Corolla): Usually brightly colored and scented to attract insects and birds for pollination.
• Stamen (Androecium): The male reproductive organ. It consists of two parts:
  • Anther: Produces yellowish pollen grains containing the male gametes.
  • Filament: A stalk that supports the anther.
• Carpel or Pistil (Gynoecium): The female reproductive organ located in the center of the flower. It consists of three parts:
  • Stigma: The sticky surface at the top that receives pollen grains.
  • Style: The tube-like structure connecting the stigma to the ovary.
  • Ovary: The swollen basal part containing ovules, which develop into seeds after fertilization.

Process of Sexual Reproduction

1. Pollination: The transfer of pollen grains from the anther to the stigma of the same flower (self-pollination) or another flower (cross-pollination) by agents like wind, water, or insects.
2. Pollen Germination: Once a pollen grain lands on a compatible stigma, it germinates to form a pollen tube that grows down through the style into the ovary.
3. Fertilization: The pollen tube enters the ovule and releases male gametes. One male gamete fuses with the female gamete (egg cell) inside the ovule. This process is called fertilization and results in the formation of a zygote.
4. Post-Fertilization Changes: The zygote divides multiple times to form an embryo. The ovule develops a tough coat and transforms into a seed. The ovary ripens and develops into a fruit, while other floral parts like petals, sepals, and stamens usually dry up and fall off.