Sexual Reproduction in Flowering Plants

• Sexual reproduction involves the formation of gametes (sperm, egg) and their fusion (fertilization).

Flowering Plants

• Flowering plants are angiosperms that produce flower, fruit and seed.
• Flowers serve aesthetic, social, cultural, religious purposes and can represent sorrow.

Flower Structure

• The final product of sexual reproduction in flowering plants is the fruit and seed.
• Floriculture is the cultivation of plants for their flowers and ornamentation.
• Common ornamental flowers include rose, chinarose, marigold, lily, jasmine, and sunflower.

Flower Formation

• Meristem is a group of actively dividing cells.
• The location of meristem is the tip/apex of the root or shoot.
• Flower formation starts with a shoot apical meristem transforming into a floral primordium or floral bud.
• Shoot apical meristem undergoes hormonal changes involving florigen and auxin.
• The shoot apical meristem undergoes slow division but the change to floral primordium involves fast division.
• The floral primordium changes into a floral meristem, which then leads to the formation of floral buds and ultimately the flower.
• Flowers are morphological and embryological marvels, characterized by their external appearance and gamete formation.

Flower Anatomy

• The structure of a flower includes several key components: Stigma, Style, Ovary (collectively forming the Pistil), Stamen, Petal, Thalamus (receptacle), Sepal, and Pedicel (stalk).

Essential vs Non-Essential Parts

• Calyx : first whorl group of the flower
• Corolla: second whorl of the flower
• Androecium: third whorl of the flower
• Gynoecium: fourth whorl of the flower
• Calyx, corolla, androecium and gynoecium are modified floral leaves.
• Androecium and gynoecium are essential (reproductive) parts of the flower
• Calyx and corolla are non-essential/accessory parts of the flower

Flower Components

• Node: Stem part of the flower where leaves originate.
• Internode: Stem part of the flower between nodes.
• Leaf of the flower arise at the node
• Internode: distance between nodes on the flower stem
• Calyx: Collection of sepals.
• Corolla: Collection of petals.
• Androecium: Collection of stamens; male reproductive structure producing male gametes.
• Gynoecium: Collection of pistils; female reproductive part.

Pre-Fertilization Events

• Before a flower appears, a plant undergoes a decision-making process to initiate flowering.
• Hormonal and structural changes occur, leading to the formation and differentiation of the floral primordium.
• Inflorescences develop, bearing floral buds that eventually become flowers.
• Androecium & gynoecium represent the male and female reproductive structures.
• The androecium consists of a whorl of stamens, representing the male reproductive organ.
• The gynoecium represents the female reproductive organ.