What is fertilization?
- Fusion of male and female gametes to form a zygote

How does fertilization takes place in a flower
• This follows pollination
• Pollen grain is deposited on the stigma
• Pollen grain sticks to the surface of the stigma
• The surface of the stigma produces a chemical substance which stimulates the pollen grain to produce a pollen tube/to germinate
• The pollen tube grows through the style tissues on which it feeds until it enters the ovary
• The generative nucleus divides into two giving two male nuclei
• Embryo sac contains eight nuclei i.e. two synergids, egg cell, two polar nuclei and three antipodal cells
• The pollen tube enters the embryo sac through the micropyle and one of the male nucleus fuses with the egg cell/ovum to form a zygote

• The other male nucleus fuses with the two polar nuclei to form the triploid nuclei/endosperm)food storage used by developing embryo)
• The pollen tube nucleus in the pollen tube disintergrates soon afterwards
• This process is referred to as double fertilization
• Zygote grows into an embryo containing plumule, radicle and cotyledons

What is double fertilization?
• This is where two male nuclei enters the embryo sac.
• One fuses with the ovum to form a zygote, while the other fuses with the polar nuclei to form a triploid primary endosperm nucleus.

• Therefore there are two fusions at fertilization Hence Double Fertilization.


Changes that Occur in a flower after fertilization
• Petals, stamen, calyx and style wither
• Ovary wall changes into pericarp
• Intergument changes into seed coat/testa
• Zygote changes into embryo (by mitosis)
• Primary endosperm nucleus changes into endosperm
• Whole ovule changes into seed
• Ovary develops and grows into fruit(under the influence of gibberrellic hormone)