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