Uptake of Water by Root Hair Cells (WJEC GCSE Biology)

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Naomi H

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Naomi H

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Importance of Water to Plants

  • Water is essential to plant survival for several reasons:
    • Photosynthesis
      • Water is a reactant in photosynthesis
    • Mineral transport
      • Minerals dissolve in water, allowing them to be easily transported when water moves from the roots to the leaves
    • Support
      • Plants that have a high water content will have turgid cells; this causes the cell vacuoles to exert outward pressure on the plant cell walls and provides essential structural support for non-woody parts of plants
      • When water availability is low plant cells can become flaccid, causing plants to wilt

Root Hair Cells & Absorption

  • Root hairs are extensions of the cells that form the outer layer of plant roots
    • These cells are known as root hair cells
  • Every root will have many root hairs, greatly increasing the root surface area available for absorption of water from the soil
  • Water enters the root hair cells by osmosis
    • Water moves into root hair cells down a water concentration gradient because there is a higher concentration of water in the soil than there is inside the root hair cells

Root hair cell diagram

root hair cell structure

Root hair cells have a large surface area, increasing the absorption of water by osmosis

Active Transport by Root Hair Cells

Higher Tier Only

  • Mineral salts, e.g. nitrates, are usually taken up by root hair cells by the process of active transport
    • This is because mineral salts are usually present at lower concentrations in the soil than inside root hair cells, so they need to be transported against their concentration gradient
  • Active transport requires energy, meaning that root hair cells must be actively respiring to release the energy needed
    • Root hair cells contain many mitochondria; the site of aerobic respiration

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Naomi H

Author: Naomi H

Expertise: Biology

Naomi graduated from the University of Oxford with a degree in Biological Sciences. She has 8 years of classroom experience teaching Key Stage 3 up to A-Level biology, and is currently a tutor and A-Level examiner. Naomi especially enjoys creating resources that enable students to build a solid understanding of subject content, while also connecting their knowledge with biology’s exciting, real-world applications.