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A plant and its lunch

What Is Inside a Seed?

A seed holds a tiny dormant plant plus enough packed food to get it started.

A tiny dormant plantA packed food storeA tough protective coat
Three parts, and that is all it needs.

  1. Step 1 of 5

    There is a whole plant already in there.

    A bean seed A complete miniatureplant, waiting

    Split a soaked bean and you can see a miniature root and shoot, fully formed. The plant is not built later — it is built already, and paused.

  2. Step 2 of 5

    Most of the seed is food.

    Food storemost of the seedThe embryo plantsurprisinglysmall

    The bulk is packed starch. A seedling cannot make its own food until it has leaves in the light, so it needs a packed lunch.

  3. Step 3 of 5

    The coat keeps it safe and asleep.

    Coat intact Dormant, sometimes fordecadesCoat breached by water Growth begins

    A tough waterproof coat blocks water and damage. It can hold a seed dormant for years — some have sprouted after centuries.

  4. Step 4 of 5

    Water is the wake-up signal.

    1 Water soaks in2 The seed swellsand splits3 Growth restarts

    Soaking swells the seed, splits the coat and restarts its chemistry. Warmth is usually needed too — the seed is checking that conditions are right.

  5. Step 5 of 5

    Root first, always.

    Shoot goes up secondreaches lightfor foodSeed food store —running downthe clock istickingRoot goes down firstsecures water

    The root goes down before the shoot goes up, so the seedling can drink before it has to feed itself. The order is not negotiable.

    Seeds sense gravity, so the root goes down whichever way up you plant them.

The short version

A seed is a dormant plant plus a food store in a tough coat, waiting for water to restart it.

Try it yourself

Soak a broad bean overnight and split it open. The little root and shoot are clearly visible with the naked eye.

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