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Seed Structure and Germination - International Baccalaureate Biology - Lecture Slides, Slides of Biology

These are the lecture slides of Biology. Key important points are: Seed Structure and Germination, External Structure, Needs for Germination, Seed Structure, Cotelydon, Plumule, Radicle, Germination, Micropyle, Testa

Typology: Slides

2012/2013

Uploaded on 01/24/2013

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Seed Structure and Germination
Internal/External Structure, Metabolic
events and Needs for Germination
Why do we have seeds?
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Seed Structure and Germination

Internal/External Structure, Metabolic events and Needs for Germination – Why do we have seeds?

Seed Development

Conditions for Germination

    1. Water is needed to:
    • Activate hormones and enzymes
    • Swelling of the seeds = bursting of seed coat.
    • Transport of simple materials to the embryo – to be used for respiration and growth.
    • Metabolic and enzyme actions – occur in solution, therefore need water.
    • Conversion of storage compounds into simple components (i.e. starch to glucose)

Conditions for Germination

    1. Suitable temperature
    • All reactions (in germination) are controlled by enzymes.
    • Optimal temperature for enzyme activity leads to faster rate of germination.
    • Freezing = inactivates enzymes
    • Very high temperatures = denatures enzymes

Metabolic Events of Germination

    1. Gibberelline activates amylase which catalyzes the break down of starch to maltose to glucose.
    1. Glucose is mobilized (transported) to the embryo.
    1. Embryo absorbs glucose and uses it for respiration (oxygen needed).
    1. Cell division, growth and elongation occurs in the embryo = radicle to root, plumule to stem.

Metabolic Events in Germination

    1. Nutrients needed for growth all supplied by food stored in cotelydons.
    1. As nutrients are consumed, first leaves start to appear = photosynthesis.
    1. When photosynthesis starts, seedling absorbs water and minerals from the soil, Co from the atmosphere and sunlight.