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Part 5: Plant reproduction

5. Imbibition

When a seed comes into contact with water it absorbs it and swells up. The seed imbibes water. Imbibe means ‘to drink’. Do not get this process mixed up with osmosis, it is not the same thing!

This is possible because of the presence of colloidal particles in the testa which attract water and cause the seed to swell.

Watch this video, paying particular attention to the seeds imbibing before they start to germinate.

Factors limiting imbibition

Temperature: The rate of imbibition increases with temperature increase.

Solute concentration: The purer the water is the higher the rate of imbibition, if the water is high in solutes (dissolved compounds) then the rate of imbibition will be low.

Why is imbibition so important?
  • It plays a key role in the initial stage of water absorption by roots when seedlings are young.
  • It initiates seed germination.
  • It plays a role in adhering water to xylem tissues.
  • It helps fruits to retain water.
  • It plays a major role in young and actively growing tissues.