Question

Distinguish between

1 absorption and conduction

2 role of humidity and wind on the rate of transpiration

Answer 1

1 ) Conduction: The transfer of heat in the direction of heat flow from one molecule to another without the actual displacement of molecules from their mean position is called conduction. Remember, molecules may vibrate at their position but never get displaced (unless change of state occurs). For example, when one end of an iron rod is heated, the other end also got heated in a short time, due to the conduction of heat.

Absorption: It is a process in which atoms , molecules or ions enters a bulk phase material. This may be physical or chemical process. e.g. Absorption of water by plant roots.

2 ) Rate of transpiration is affected by changes in humidity, wind speed, temperature and light intensity. Among these relative humidity of atmosphere is the most influential in determining the rate of transpiration. When humidity is less, atmosphere will be less moist and it increases the driving force for transpiration.When humidity is high, the atmosphere contains more moisture and it decreases the driving force for transpiration. As velocity of wind increases the rate of movement of water from the leaf surface increases and so the transpiration also increases. High wind velocity and high light intensity increases the rate of transpiration. Relative humidity can also regulate water and temperature of environment.