Water Transports in Plants

• What is one of the roles of water in plants?

  Provides hydrostatic pressure to support stem
• Why is water needed for photosynthesis?

  It is a reactant in the photosynthesis process
• How does water contribute to the transport of mineral ions in plants?

  It transports mineral ions from roots and the products of photosynthesis
• What effect does evaporating water have on plants?

  It keeps plants cool and aids the movement from root to leaves
• How does water drive cell expansion in plants?

  It allows plants to force their roots into compact soil
• What is the water potential in root hair cells compared to the soil?

  The water potential in the root hair cells is lower (more negative) than in the soil
• How do root hair cells reduce their water potential?

  By actively transporting mineral ions such as nitrates into the cell
• What happens to water after it moves into the root hair cells?

  Water moves through the root cortex and endodermis into the xylem
• What is the symplast pathway in water movement?

  Water moves in the cytoplasm of cells and from cell to cell via plasmodesmata
• How does water move through the apoplast pathway?

  Water moves through the cell walls and spaces between cells
• What happens when water reaches the endodermis layer in the apoplast pathway?

  It is stopped by the Casparian strip, forcing it to enter the cells
• What is the Casparian strip?

  A waxy layer of waterproof suberin in the cell wall
• What is the role of the endodermis in water movement?

  It surrounds the xylem and regulates water entry into it
• How do endodermis cells move ions into the xylem?

  By active transport from the surrounding environment
• What effect does active transport have on water potential in the xylem?

  It lowers the water potential in the xylem
• How does water move from the endodermis to the xylem?

  By osmosis
• What happens to the water potential outside the endodermis cells?

  It reduces, causing water to move in
• What is the pathway of water movement from root hair cells to the xylem?

  Water moves along the symplast pathway from root hair cells, across the cortex into the xylem
• What is the simultaneous movement of water across the cortex?

  Water can move via the apoplast pathway into cells to join the symplast pathway
• What are the three main mechanisms of water movement up the stem?

  Root pressure, transpiration pull, and capillary action
• How does water movement occur in relation to water potential and hydrostatic pressure gradients?

  It occurs down a water potential gradient and down a hydrostatic pressure gradient