1. Importance of Flowers

Flowers have been closely associated with human beings since ancient times. They have:

• Aesthetic value – beauty and decoration
• Ornamental value – used in homes and gardens
• Social value – used in ceremonies and celebrations
• Religious value – used in worship
• Cultural value – associated with traditions and festivals
• Used to express love, affection, happiness, grief and mourning

2. Examples of Ornamental Flowers

Commonly cultivated at homes and in gardens:

1. Rose
2. Marigold
3. Jasmine
4. Hibiscus
5. Petunia

3. Floriculture

Floriculture is the branch of horticulture concerned with the cultivation and management of flowering plants and ornamental flowers.

4. Biological Importance of Flowers

To a biologist, flowers are:

• Morphological marvels
• Embryological marvels
• The sites of sexual reproduction in angiosperms.

5. Two Important Reproductive Parts

The two parts of a flower in which the important units of sexual reproduction develop are:

Flower part	Reproductive unit
Androecium	Pollen grains (male gametophytes)
Gynoecium	Embryo sac (female gametophyte)

6. Pre-fertilisation: Structures and Events

Before the flower becomes visible, the plant undergoes hormonal and structural changes that initiate flowering.

Sequence:

Hormonal & structural changes → Floral primordium → Inflorescence → Floral buds → Flowers

In the developing flower:

• Androecium → male reproductive structure
• Gynoecium → female reproductive structure

Both differentiate and develop before fertilisation.

Individual part	Collective term / Whorl
Petal	Corolla
Sepal	Calyx
Carpel	Gynoecium
Stamen	Androecium

Easy way to remember 🌸

Petals → Corolla
Sepals → Calyx
Carpels → Gynoecium
Stamens → Androecium

👉 Calyx + Corolla = Accessory/Non-reproductive whorls
👉 Androecium + Gynoecium = Reproductive whorls

⭐ Key Flow

Flowering decision → Floral primordium → Inflorescence → Floral bud → Flower → Androecium + Gynoecium

Stamen — key points from the diagram

• Stamen = male reproductive organ of a flower.
• It consists of two parts:
  1. Anther
  2. Filament

Anther

• Typically bilobed.
• Each anther has 2 lobes.
• Therefore, one anther generally has 4 microsporangia (pollen sacs).
• Each lobe is dithecous → each lobe contains 2 thecae.
• Theca = a pollen-bearing half/lobe of the anther.

Filament

• A stalk-like structure that supports the anther.
• It connects the anther to the flower.

1. Sporophyte (2n)

• The sporophyte is the diploid (2n) plant body.
• It produces spores.
• Special cells in the sporophyte undergo meiosis.

2. Meiosis → Spores (n)

• Meiosis reduces the chromosome number: 2n → n
• Therefore, the spores are haploid (n).
• These spores are produced in spore-forming structures of the sporophyte.

3. Spore → Gametophyte (n)

• A haploid spore grows and develops into a gametophyte.
• The gametophyte is therefore haploid (n).

4. Gametophyte → Gametes (n)

• The gametophyte produces gametes by mitosis, not meiosis.
• Since the gametophyte is already haploid: n → n

Remember:

Ovary → Fruit
Ovule → Seed
Ovary wall → Pericarp
Integuments of ovule → Seed coat