Movement of water through xylem

• What can root pressure do in the xylem?

  Push water up against gravity
• What is guttation in plants?

  Water forced out at leaf tips
• What causes root pressure?

  Active transport of ions into the stele
• How does water flow into the roots?

  By passive flow due to water potential
• Why is root pressure limited in tall plants?

  Gravity counteracts the upward pressure
• What is the main theory explaining water movement in the xylem?

  Cohesion-tension theory
• What type of molecules is water?

  Polar molecules
• What forms between negative oxygen and positive hydrogen atoms in water?

  Hydrogen bonds
• What is cohesion in water molecules?

  Water molecules stick together
• What is adhesion in water molecules?

  Water attracted to charged/polar molecules
• What is the transpiration stream?

  A constant stream of water from roots to leaves
• What happens to stomata during the day?

  They open to let CO2 in
• What occurs when water vapor leaves the plant?

  It lowers the water potential in leaves
• What creates a water potential gradient in plants?

  Difference in water potential between soil and air
• How is water lost from leaves replaced?

  By evaporation from mesophyll cells
• What happens as water evaporates from the leaves?

  It is replaced by water from mesophyll cells
• What role do adhesive and cohesive properties of water play?

  They maintain a continuous water column
• What creates tension in the xylem water column?

  Evaporation of water from leaves
• How does cohesion transmit pulling force in water?

  It connects water molecules throughout the xylem
• How does adhesion help in water movement?

  It resists gravity by sticking to xylem walls
• What is the waterproof band in the endodermis called?

  Casparian Strip
• What is the function of the Casparian Strip?

  It blocks water from the apoplast pathway
• What does the Casparian Strip force water to enter?

  The symplast pathway
• How does water move through the symplast pathway?

  Through the cytoplasm and plasmodesmata
• Why is it important for plants to control which substances enter the xylem?

  To absorb essential minerals and prevent harm
• What process creates a lower water potential in endodermal cells?

  Active transport of minerals
• Which minerals are actively transported into the cytoplasm?

  Potassium and nitrate
• How does lower water potential in endodermal cells affect water movement?

  It helps draw in water by osmosis
• What is the overall effect of the regulated movement of water into the xylem?

  It allows absorption of essential minerals
• What does the regulation of water movement prevent?

  Harmful substances from entering the vascular system
• What is suberin?

  A waterproof substance in the endodermis
• What does the apoplast pathway refer to?

  Spaces between cell walls
• What is the role of plasmodesmata?

  They connect the cytoplasm of adjacent cells
• What is the function of the xylem?

  Transporting water and minerals
• What is osmosis?

  Movement of water across a membrane
• How is the movement of water from soil to xylem described?

  It is carefully regulated