The process of transpiration is when water moves through plants from the roots to the leaves, then changes to vapor as it leaves the plant. Transpiration cools the plant and also provides it with nutrients, carbon dioxide and water. Water is necessary for plants but only a small amount of water taken up by the roots is used for growth and metabolism.

The rate of transpiration is dependent on a few different factors:

Temperature

As the temperature increases, the transpiration rate goes up. The openings in the plant that release the vapor are called stoma, and when the temperature is warm, the stoma are open. Colder temperatures cause the stoma to close.

Relative humidity

Because it is difficult for vapor to be released into damp air, the less humid it is, the higher the rate of transpiration.

Wind and air movement

The transpiration rate increases with increased air movement. One reason is because air movement is constantly bringing drier air close to the plant, which relates to relative humidity.

Soil and moisture availability

If the soil does not have enough water, the transpiration rate decreases.

 

Type of plant

The transpiration rate differs depending on the type of plant. Cacti, for example, conserve water and have low transpiration rates.

The process of transpiration is a very important procedure for plants. It creates a negative pressure gradient that helps draw water and minerals up through the plant from its roots. It also helps to keep the plants cool during hot weathers – a method of evaporation cooling.

Xylem – The vascular tissue in plants which conducts water and dissolved nutrients upwards from the root and also helps to form the woody element in the stem.

Stomata – Any of the minute pores in the epidermis (the outer layer of a tissue in a plant) of the leaf or stem of a plant, forming a slit of variable width which allows movement of gases in and out of the intercellular (located or occurring between cells) spaces.

Transpiration and water loss from leaves happen because of the way that leaves are adapted for efficient photosynthesis. The flat, thin shape of a leaf, its spongy mesophyll (the inner tissue of a leaf, containing many chloroplast) layer and stomata are adaptations that also allow water loss from the leaf.