Factors affecting transpiration

• The stem, root and leaves form an organ system that transports substances into, around and out of a plant.
• The rate of transpiration is affected by several factors including temperature, humidity, air movement, and light intensity.
• Increasing temperature increases molecular movement so that more water molecules evaporate from cell surfaces and the rate of diffusion of water molecules from the leaf is increased.
• Decreasing humidity reduces the concentration of water molecules outside the leaf, causing more water to diffuse from the leaf.
• Increasing air movement removes water vapour from leaf surfaces, causing more water to diffuse from the leaf.
• Increasing light intensity increases the rate of photosynthesis, causing stomata to open and water to diffuse out of the leaf.
• Plants living in different habitats have adaptations to resist extremes of these factors.
• Conditions that decrease the rate of transpiration include a decrease in temperature, an increase in humidity, no or reduced air movement, and low light intensities.