During the process of transpiration, plants absorb water through their roots, and then distribute that water to their leaves by moving the water up through the stem, and then the leaves release that moisture by evaporation.

Ten per cent of all atmospheric moisture comes from plant transpiration with the remaining 90 per cent a result of evaporation of bodies of water such as oceans and lakes.

Plants utilize water at different rates so the process of transpiration is relative to the amount of water a specific plant uses. A water plant, for example, uses water at a much higher rate than a plant that grows in a more arid climate.

Atmospheric conditions (temperature, wind, and relative humidity) play a large part in determining the transpiration rate.

Higher temperatures stimulate the plant’s pores to open, which triggers a higher rate of transpiration and water usage, whereas cooler temperatures cause the pores to close, which conserves moisture.

Almost all transpiration occurs during sunny, warm afternoons and very little occurs during the cooler evenings. In arid climates plants use this break in heat and transpiration to regain moisture from the atmosphere, as well as through their root system.

Since most roots are above the geographical water table, almost all moisture for most plants is provided by rainfall.