Transport in Plants - Xylem

• Xylem tissue transports water and mineral ions in solution

  These substances move up the plant from the roots to the leaves
• • Phloem tissue transports organic substances like sugars both up and down the plant
• Xylem vessels are the part of the xylem tissue that actually transports the water and ions

  Xylem vessels are very long, tube-like structures formed from dead cells joined end to end

  There are no end walls, interrupted tube that allows water to pass up through the middle easily
• Cohesion and tension

  1. Water evaporates from the leaves at the top of the xylem. This is a process called transpiration
  2. This creates tension which pulls more water into the leaf
  3. Water molecules are cohesive so when some are pulled into the lead others follow. This means the whole column of water in the xylem, from the leaves down to the roots move upwards
  4. Water then enters the stem through the roots
• Transpiration is the evaporation of water from a plants surface, especially the leaves.

  Water evaporates from the moist cell walls and accumulates in the spaces between the cells in the leaf

  When the stomata open it moves out of the leaf down the water potential gradient as there is more water inside the lead than in the air outside