Fertilization in Plants

Dr. Pramila Kudva

Structure of a mature pollen grain

Germination of Pollen Grain

Components of a mature pollen

Mature pollen has Outer coveirng – ExineInner covering – IntineAn opening – Germ PoreA Generative and a tube nucleusGenerative Nucleus divides into two Sperm Nuclei

Structure of a

mature Ovule

• 2 protective integuments• Integuments enclose Nucellus • Small opening in the integument – Micropyle• The Embryo Sac encloses

– 3 antipodal cells– Central cell with 2 polar Nuclei– Egg cell and 2 synergids

Components of a mature Ovule

Double Fertilization

• To view video of double fertilization • https://www.youtube.com/watch?v=bUjVHUf

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• Double fertilization includes two fertilizations• Fertilisation 1 – Sperm nucleus [1N] fuses with

the egg cell [1 N] to form the zygote [2N]• Fertilisation 2 – Sperm nucleus [1N] fuses with

the secondary nucleus [2N]. • Triple Fusion - 2 polar nuclei unite to form a

secondary nucleus and this unites with the sperm to form the endosperm cell. This involves the fusion of 3 nuclei and hence called Triple fusion

• After fertilization– The corolla, stamens, style and stigma generally

fall off.– The calyx may remain in some plants – Apple,

Guava– Ovary enlarges to form a fruit – it could be hard or

fleshy– Single ovule produces single seeded fruit – Many ovules produce many seeded fruit– Seeds are attached to the ovary by means of

Placenta

Part of the Flower After fertilisation

1. Ovary Fruit

2. Ovary Wall Pericarp

3. Ovule Seed

4. Placenta Stalk of the seed

5. Integuments Seed coat

6. Secondary nucleus Endosperm [Food storing tissue]

7. Egg Cell Zygote