Plants have many important functions, like making leaves, making flowers and seeds, growing, storing starches in the roots etc, but we humans are usually unaware of the vital function of transpiration.It is estimated that 98% of a plants energy is used in the work of transpiration. How does this process work? and why is it so essential to a plant?Water moves from the soil into plant roots, up through the sapwood into the leaves. The water, warmed by the sun, turns into vapor (evaporates), and passes out through thousands of tiny pores (stomata) mostly on the underside of the leaf surface. This is transpiration. It has two main functions: cooling the plant and pumping water and minerals to the leaves for photosynthesis.
A leaf transpires about 90% of the water evaporated from a water surface of the same area—even though the combined area of stomatal pores is only 1-2% of the total leaf area.Transpiration rates are highest in leaves that are stiff with turgor (water pressure). When leaves wilt, they offer less surface area to sun exposure, and thus will transpire less, saving water. Watch a tough, drought-tolerant plant like lilac when temperatures are high for a demonstration of this water-saving strategy.Succulents save water by opening the stomata pores at night to reduce transpiration and to take in carbon dioxide which is stored in their leaves until the next day when they can photosynthesize.