Water and ion uptake in plants

• How can water be absorbed by root hair cells?

  Passively into the cell wall or by osmosis
• What must water cross from the epidermis to reach the xylem?

  The root cortex
• What are the three routes water can take across the cortex?

  Apoplast, symplast, and vacuolar routes
• How does water move through the apoplast route?

  By diffusion through the cell walls
• Why is the apoplast route the fastest for water movement?

  Less resistance due to no membranes
• What prevents water from continuing along the apoplast route at the endodermis?

  The Casparian strip's waterproof layer
• What is the Casparian strip made of?

  A waxy substance called suberin
• How does water move through the symplast route?

  By osmosis into the cytoplasm
• What is the vacuolar route for water movement?

  Movement between cytoplasm and vacuole
• Why is the vacuolar route the slowest for water movement?

  Resistance increases with membrane crossings
• How do water pathways interact as water moves across the root?

  Water can move between apoplast, symplast, and vacuolar routes
• Why is the concentration of ions in soil usually lower than in plant cells?

  Soil particles attract charged ions
• How do ions typically enter plant cells at root hair cells?

  Via the symplast route
• What happens to ion movement at the endodermis due to the Casparian strip?

  All ions must enter the cytoplasm
• What mechanisms are used to move ions into the cytoplasm?

  Active transport and co-transport
• How do ions move into the xylem after entering the cytoplasm?

  Along the symplast route
• What effect does increasing ion concentration in the stele have on water potential?

  It lowers the water potential
• How does lowering water potential in roots affect water absorption?

  It increases the amount of water absorbed