Transpiration

Everyday, a large tree loses about 1,000 litres of water form its body by way of evaporation. This loss of excess water is essential for the survival of tree. If the water were to accumulate in the plant tissues, hydrostatic pressure would build up in the cells and eventually cause it to rupture. The metabolic activity of the plant would be affected and the plant would soon perish.

Also, when water is lost by evaporation, heat energy is taken up from the plant body to vaporise the water, thereby cooling the plant. The addition of moisture in the atmosphere cools the environment and influences climate. The water that falls to the ground as rain and is absorbed by the roots is returned to the atmosphere and the water cycle is completed.

The method by which plants lose water in the form of water vapour from their aerial surfaces is known as transpiration.

It is a vital process, both, to plants and to the environment, and consequently to humans.

A rainforest generates its own water cycle. Rain that falls on the canopy drips through the undergrowth and into the soil. There the water is rapidly taken up by the roots and again released through the leaves by transpiration. In the air above, the moisture forms clouds and soon falls as rain again, thus completing the water cycle.

Without the forest, the rain will cease to fall in these areas, and this will probably result in changes to the climate of other regions.

The removal of rainforests will also contribute greatly to the greenhouse effect andglobal warming, and the destruction of thousands of species that live in this habitat.

However, there are certain plants that grow in arid regions and need to conserve the water. Such plants, known as xerophytes, develop mechanisms that enable them to survive under such conditions.

Their leaves (main part concerned with transpiration) are completely shed or reduced in surface area by undergoing modifications (spines, needles, etc.).