Main Organ for Transpiration

2.3 Main Organ for Transpiration
  1. Transpiration is the loss of water as water vapour from plants especially from leaves to surrounding through evaporation
  2. Leaves serve as the main organ to ensure transpiration takes place in plants
  3. The importance of transpiration:
  • Ensures water and mineral salts can be transported continuosly within vascular tissues
  • Supplies water to spongy mesophyll cells for photosynthesis
  • Supplies water and mineral salts for cell development and growth
  • Gives cooling effect to plants

Environmental factor that affect the rate of transpiration:

Light intensity:
  • In daylight, light intensity is high, this wil stimulate opening of stomata and then increases the rate of transpiration
  • At a light intensity where the rate of transpiration is maximum, the increasing in light intensity does not increase the rate of transpiration because all stomata are opened
  • The opening of stomata due to high light intensity is to uptake more carbon dioxide for photosynthesis
  • Kinetic energy of water molecules increses when the surrounding temperature increases
  • When the surrounding temperature increases,water vapour in air spaces diffuse rapidly into surrounding through osmosis
  • The rate of transpiration increases
  • When the surrounding temperature too high,the rate of transpiration decreases due to closing of stomata to conserve water in plants
Movement of air:
  • A rapid movement of air remove water vapour from leaves rapidly
  • The water vapour in air spaces diffuses out rapidly
  • The rate of transpiration decreases
Relative humidity of air:
  • When the relative humidity of surrounding air is lower than those in air spaces within leaves, the water vapour within air spaces diffuses out rapidly. Thus, the rate of transpiration is high
  • As the relative humidity of surrounding air increases, the water vapour within the air spaces diffuses out is slower. Thus,the rate of transpiration decreases.