transpiration and translocation

• transpiration

  loss of water vapour from a plant's surface by evaporation and diffusion
• translocation

  movement of food and other substances through a plant's phloem tissue
• transpiration

  1. water evaporates from spongy mesophyll cells into the air spaces that surround the cells
  2. the water vapour then diffuses through open stomata into the air around the leaf
• transpiration stream

  continuous movement of water into plant through its roots, through its xylem tissue and out of its leaves
• transpiration stream

  1. water is lost at the leaves by transpiration
  2. to replace the lost water, water is drawn out of xylem into the leaves
  3. root hair cells draw in water from the soil by osmosis to replace water in the xylem
• light intensity

  as light intensity increases the rate of transpiration also increases this is because stomata open as light intensity rises which increases the amount of water lost by transpiration
• temperature

  as temperature increases the rate of transpiration also increases this is because water molecules will have more kinetic energy at higher temperatures so more water molecules evaporate and diffuse out of a plant in a given time compared to at lower temperature
• humidity

  as humidity decreases the rate of transpiration increases this is because at low humidity the concentration gradient of water between a plant and the air around is greater than at high humidity so the rate of diffusion is higher
• air flow

  as air flow increases the rate of transpiration also increases this is because when more air flows around a plant more water vapour is carried away from the plant