Question

Processes occur in leaves, which may lower their temperature is

• A. Respiration
• B. Photosynthesis
• C. Hydrolysis
• D. Transpiration

Answer 1

Answer: (D)

Transpiration

Transpiration is loss of water in vapour form through stomata. Rate of transpiration depends on a number of factors, like carbon dioxide concentration, temperature, light, humidity etc. The most important factor, which governs rate of transpiration is the vapour pressure gradient, which exists between leaf mesophyll and atmosphere. It has been estimated, that almost 99 percent of water absorbed by plants is lost in transpiration. As transpiration generates the tension, which is the most important force responsible for water absorption. It is more correct to say almost 99 percent of water absorbed by plants is due to transpiration. Transpiration sets the streaming of water and minerals in vascular bundles and is responsible for ascent of sap from roots to leaves. Besides this transpiration also cools down the surface of leaves.