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Grade 6 Beginner About 15 min Version 1 Awaiting review Premium

How do roots grow best?

Roots anchor a plant and take in water and mineral salts from the soil. Root cells also need oxygen from the air spaces in the soil. Loamy soil, a mixture of sand, clay and humus, holds water but still has air spaces, so roots grow well in it. Sandy soil drains quickly and dries out. Clay soil is heavy and packs tightly, so roots push through it slowly, and when it is waterlogged the air spaces fill with water and the roots cannot breathe.

What you will learn

  • Measure and compare root growth.
  • Explain how soil type affects root growth.
  • Explain why both too little and too much water slow root growth.

Before you start

  • Know the parts of a plant and the main types of soil.

Materials

  • Maize or bean seeds
  • Sandy soil, loamy soil and clay soil

Equipment

  • Clear plastic cups or bottles cut as pots, a ruler

Procedure

  1. Water three pots of sandy, loamy and clay soil the right amount. Measure the roots after 14 days.
  2. In loamy soil, give a little water, the right amount and too much. Measure the roots after 14 days.

How this simulation is simplified

  • In the best conditions the main root grows 6 mm a day; poorer conditions slow it by a fixed fraction.