why do plants evaporate 90% of water during stomatal transpiration?

Asked by krittikac02 | 16th Jul, 2009, 07:56: PM

Expert Answer:

Transpiration is an inevitable, but potentially harmful, consequence of having moist mesophyll membranes exposed to the atmosphere. Despite its apparent inevitability, transpiration is of great significance for the plant. Water is conducted in most plants due to transpiration pull. Minerals dissolved in water are distributed throughout plant body by transpiration. Evaporation of water from the exposed surface of cells of leaves has cooling effect on plant. Wet surface of leaf cells allow gaseous exchange.

More than 90% of the water taken in by the plant root is ultimately lost to the atmosphere. Most of the water is lost from the leaves through the stomata, in the form of water vapor. The rate of transpiration is directly related to the degree of stomatal opening, and to the evaporative demand of the atmosphere surrounding the leaf. The amount of water lost by a plant depends on its size, along with the surrounding light intensity, temperature, humidity, and wind speed (all of which influence evaporative demand). Soil water supply and soil temperature can influence stomatal opening, and thus transpiration rate. There are ways to limit transpiration, as can be seen in desert plants.

Answered by  | 18th Jul, 2009, 07:37: AM

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