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.