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How imbibition pressure helps in germination of seeds?

GeneralClass 12AllAnswered 27 Mar 2026
Answer

Imbibition plays a crucial role in seed germination through the following mechanism:

Step-by-Step Process:

  1. Dry Seed Characteristics:
    • Extremely negative water potential (Ψ<sub>w</sub> ≈ –100 to –300 MPa)
    • High concentration of hydrophilic colloids (proteins, starch)
    • Strong affinity for water
    • Metabolically dormant
  2. Water Imbibition:
    • When placed in water (Ψ<sub>w</sub> = 0), steep water potential gradient drives rapid water uptake
    • Water molecules form hydrogen bonds with hydrophilic macromolecules
    • Seed volume increases by 200-300%
  3. Imbibition Pressure Development:
    • Tremendous pressure generated (up to 1000 atmospheres)
    • Causes mechanical rupture of seed coat (testa)
    • Creates space for radicle emergence
  4. Metabolic Activation:
    • Water activates enzymes (amylases, proteases)
    • Hydrolysis of stored food (starch → glucose)
    • Respiration resumes
    • Embryo growth initiated

Biological Significance:

  • First critical step in germination
  • Ensures radicle emergence even in hard soil
  • Demonstrates physical force of water

Classical Example: Ancient Egyptian wheat seeds germinated after 3000 years due to intact imbibition capacity.

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General · Class 12