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

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

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