Transpiration Rate

• Transpiration rate is affected by three main things:


  1. An increase in light intensity
  2. An increase in temperature
  3. An increase in air movement
• Increase in light intensity


  The brighter the light, the greater the transpiration rate.

  Bright light increases the rate of photosynthesis, causing the stomata to open to let CO2 in.

  Stomata begin to close as it gets darker because photosynthesis can't happen in the dark.

  When the stomata are closed, water can't escape
• Increase in temperature


  The warmer it is, the faster transpiration occurs.

  When it's warm, the water particles have more energy to evaporate and diffuse out of the stomata.
• Increase in air movement


  If there's a lot of air movement ( wind ) around a leaf, transpiration happens faster.

  If the air around a leaf is still, the water vapour just surrounds the leaf and doesn't move away; there's a high concentration of water particles outside the leaf as well as inside it, so diffusion doesn't occur as quickly.
• Increase in air movement


  If it's windy, the water vapour is swept away, maintaining a low concentration of water in the air outside the leaf.

  Diffusion then happens quickly, from an area of higher concentration to an area of lower concentration