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Questions and Answers
What is the primary reason why water enters the root hair cells from the surrounding soil?
What is the function of the root cortex cells in the process of water uptake?
What is the primary mechanism by which water moves up the stem in the xylem?
What is the result of a water molecule leaving the xylem and moving into a cell of the leaf?
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What is the term used to describe the movement of water from the root hair cells to the xylem vessels?
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Why is the water potential gradient not sufficient to move water up the stem?
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What is the term used to describe the tendency of water molecules to stick to each other?
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What is the result of the tension created in the xylem when a water molecule leaves the xylem and moves into a cell of the leaf?
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Study Notes
Water Uptake
- Water concentration is higher outside the root in the soil than inside the root hair cells, creating a higher water potential outside.
- Water enters the root hair cells by osmosis, moving down the water potential gradient.
- Root hair cells have a large surface area due to their long, thin shape, increasing the uptake of water and mineral ions.
Water Movement Through the Plant
- Water moves from the root hair cells to the root cortex cells due to a lower water potential in the cortex cells.
- Water moves down the water potential gradient by osmosis through the cortex cells and into the xylem vessels.
- Once in the xylem, water moves up the plant to the leaves in a transpiration stream.
- In the leaves, water moves out of the xylem in the vascular bundle and into the spongy mesophyll cells by osmosis.
Water Potential Gradient Limitations
- A water potential gradient is not enough to move water very far, only working for water moving into roots from the soil and from the xylem through the leaf.
- The root cannot create a pressure to push the water up the stem.
Transpiration Stream
- Water pulls itself up the xylem in the stem due to cohesion and tension.
- Cohesion is the tendency for water molecules to stick to each other, forming a column of water molecules in the xylem (transpiration stream).
- When a water molecule leaves the xylem and moves into a leaf cell, it creates tension, pulling the water molecules up the xylem.
- This tension extends all the way down to the roots, pulling water out of the cortex cells into the xylem, which lowers the water potential of the cortex cells.
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Description
Learn about the process of water uptake in root hair cells, including the role of osmosis and the importance of surface area.
