CBSE · Class 10 · Science · How do Organisms Reproduce?Explain the process of sexual reproduction in flowering plants with the help of a well-labeled diagram concept. Describe the various parts of a flower and the post-fertilization changes that take place in the flower.

Introduction to Sexual Reproduction in Flowering Plants\nSexual reproduction in flowering plants involves the production of male and female gametes, the transfer of male gametes to the female ovule, fertilization, and the development of seeds and fruits. Flowers are the reproductive organs of angiosperms.

Parts of a Flower\nA typical flower consists of four main whorls attached to a swollen stalk called the thalamus:

• Sepals (Calyx): The outermost green, leaf-like whorl that protects the flower in the bud stage.
• Petals (Corolla): Usually brightly colored and scented to attract insects and birds for pollination.
• Stamens (Androecium): The male reproductive organ consisting of a slender filament and a pollen-bearing anther. Pollen grains contain the male gametes.
• Carpels or Pistil (Gynoecium): The female reproductive organ consisting of three parts: stigma (sticky surface to receive pollen), style (tube connecting stigma to ovary), and ovary (contains ovules with female gametes/egg cells).

Process of Fertilization

1. Pollination: The transfer of pollen grains from the anther to the stigma of the same flower (self-pollination) or a different flower of the same species (cross-pollination) by agents like wind, water, or insects.
2. Germination of Pollen: 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. Syngamy: The male gamete travels down the pollen tube and fuses with the female egg cell inside the ovule to form a zygote.

Post-Fertilization Changes\nFollowing fertilization, several structural changes occur in the flower:

• The zygote divides multiple times to form an embryo inside the ovule.
• The ovule develops a tough coat and transforms into a seed.
• The ovary enlarges, ripens, and develops into a fruit.
• Other parts such as sepals, petals, stamens, style, and stigma typically dry up and fall off.