Biology of Flowers

Structure of a Flower

• A flower is a modified shoot that is the reproductive part of a plant.
• It consists of four whorls: calyx, corolla, androecium, and gynoecium.

Whorls of a Flower

• The calyx is the outermost whorl formed from sepals.
• The corolla is the second whorl formed from petals.
• The androecium is the male reproductive whorl, formed from stamens.
• The gynoecium is the female reproductive whorl, formed from carpels or pistils.

Types of Flowers

• Complete flowers have all four whorls and are bisexual.
• Flowers with only the male reproductive whorl are called male flowers.
• Flowers with only the female reproductive whorl are called female flowers, and are incomplete or unisexual.

Reproduction in Flowers

• Pollen grains are male gametes formed in the stamen.
• Pollination is the transfer of pollen grains from anther to stigma of a flower.
• There are two types of pollination: self-pollination and cross-pollination.
• Pollination can occur through insects, water, wind, or animals.
• Fertilization is the fusion of male and female gametes.

Fruits and Seeds

• The ovary changes into fruit and the ovules change into seeds after fertilization.
• Each seed contains an embryo that develops into a new plant.
• Seeds are dispersed by wind, water, animals, and humans.
• Dicotyledonous seeds have two cotyledons, while monocotyledonous seeds have one cotyledon.

Seed Germination

• Seed germination is the process of activating the inactive embryo and its growth into a seedling.
• The plumule part of the embryo grows to form the shoot, and the radicle grows into the root of the plant.
• In epigeal germination, the cotyledons form the first green leaves of the seedling.
• In hypogeal germination, the cotyledons remain underground and do not form leaves.
• Seed germination requires water, oxygen, and a suitable temperature.

Key Terms

• Pedicel: the stalk of the flower.
• Thalamus: the swollen structure in the flower that bears all the floral whorls.
• Plumule: the part of the embryo that grows into the shoot.
• Radicle: the part of the embryo that grows into the roots.
• Cotyledons: the seed leaves.
• Epigeal: a type of germination when the cotyledons come out of the soil.
• Hypogeal: a type of germination when the cotyledons remain under the soil.

Structure of a Flower

• A flower is a modified shoot that is the reproductive part of a plant.
• It consists of four whorls: calyx, corolla, androecium, and gynoecium.

Whorls of a Flower

• The calyx is the outermost whorl formed from sepals.
• The corolla is the second whorl formed from petals.
• The androecium is the male reproductive whorl, formed from stamens.
• The gynoecium is the female reproductive whorl, formed from carpels or pistils.

Types of Flowers

• Complete flowers have all four whorls and are bisexual.
• Flowers with only the male reproductive whorl are called male flowers.
• Flowers with only the female reproductive whorl are called female flowers, and are incomplete or unisexual.

Reproduction in Flowers

• Pollen grains are male gametes formed in the stamen.
• Pollination is the transfer of pollen grains from anther to stigma of a flower.
• There are two types of pollination: self-pollination and cross-pollination.
• Pollination can occur through insects, water, wind, or animals.
• Fertilization is the fusion of male and female gametes.

Fruits and Seeds

• The ovary changes into fruit and the ovules change into seeds after fertilization.
• Each seed contains an embryo that develops into a new plant.
• Seeds are dispersed by wind, water, animals, and humans.
• Dicotyledonous seeds have two cotyledons, while monocotyledonous seeds have one cotyledon.

Seed Germination

• Seed germination is the process of activating the inactive embryo and its growth into a seedling.
• The plumule part of the embryo grows to form the shoot, and the radicle grows into the root of the plant.
• In epigeal germination, the cotyledons form the first green leaves of the seedling.
• In hypogeal germination, the cotyledons remain underground and do not form leaves.
• Seed germination requires water, oxygen, and a suitable temperature.

Key Terms

• Pedicel: the stalk of the flower.
• Thalamus: the swollen structure in the flower that bears all the floral whorls.
• Plumule: the part of the embryo that grows into the shoot.
• Radicle: the part of the embryo that grows into the roots.
• Cotyledons: the seed leaves.
• Epigeal: a type of germination when the cotyledons come out of the soil.
• Hypogeal: a type of germination when the cotyledons remain under the soil.

Structure of a Flower

• A flower is a modified shoot that is the reproductive part of a plant.
• It consists of four whorls: calyx, corolla, androecium, and gynoecium.

Whorls of a Flower

• The calyx is the outermost whorl formed from sepals.
• The corolla is the second whorl formed from petals.
• The androecium is the male reproductive whorl, formed from stamens.
• The gynoecium is the female reproductive whorl, formed from carpels or pistils.

Types of Flowers

• Complete flowers have all four whorls and are bisexual.
• Flowers with only the male reproductive whorl are called male flowers.
• Flowers with only the female reproductive whorl are called female flowers, and are incomplete or unisexual.

Reproduction in Flowers

• Pollen grains are male gametes formed in the stamen.
• Pollination is the transfer of pollen grains from anther to stigma of a flower.
• There are two types of pollination: self-pollination and cross-pollination.
• Pollination can occur through insects, water, wind, or animals.
• Fertilization is the fusion of male and female gametes.

Fruits and Seeds

• The ovary changes into fruit and the ovules change into seeds after fertilization.
• Each seed contains an embryo that develops into a new plant.
• Seeds are dispersed by wind, water, animals, and humans.
• Dicotyledonous seeds have two cotyledons, while monocotyledonous seeds have one cotyledon.

Seed Germination

• Seed germination is the process of activating the inactive embryo and its growth into a seedling.
• The plumule part of the embryo grows to form the shoot, and the radicle grows into the root of the plant.
• In epigeal germination, the cotyledons form the first green leaves of the seedling.
• In hypogeal germination, the cotyledons remain underground and do not form leaves.
• Seed germination requires water, oxygen, and a suitable temperature.

Key Terms

• Pedicel: the stalk of the flower.
• Thalamus: the swollen structure in the flower that bears all the floral whorls.
• Plumule: the part of the embryo that grows into the shoot.
• Radicle: the part of the embryo that grows into the roots.
• Cotyledons: the seed leaves.
• Epigeal: a type of germination when the cotyledons come out of the soil.
• Hypogeal: a type of germination when the cotyledons remain under the soil.

Learn about the structure and function of flowers, including the different whorls and their reproductive roles. Understand the characteristics of complete, male, and female flowers.