1.6
Fertilisation
Seed formation When the male nucleus fuses with the female nucleus inside an ovule, it produces a zygote. embryo plant
The zygote starts to divide. It produces a little group of cells called an embryo. This embryo will eventually grow into a new plant. The ovule also begins to change. It gradually grows into a seed.
seed zygote ovule How a seed is formed.
Activity 1.6 Investigating seed structure Beans are seeds. You are going to look carefully at the structure of a bean seed. It is easier to do this if the bean has been soaked in water for a few hours first, to soften it. 1 Look carefully at the bean seed. Find the structures shown on the diagram. The testa is the tough outer coat of the seed. The micropyle is a tiny hole where the pollen tube grew into the ovule. (Remember – the seed began as an ovule.) 2 Peel the testa away from the seed. Inside, you should find two creamy-coloured structures. These are called cotyledons. They contain food stores for the embryo to use when it starts to grow. 3 Gently pull the cotyledons apart. You will find the embryo plant in between them.
testa micropyle A bean seed.
scar
cotyledons Bean seed with testa removed.
embryo plant One cotyledon removed.
Summary
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1 Plants
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