Importance of Transpiration
It provides the water needed for food manufactured by photosynthesis in the leaves.
Transpiration involves the evaporation of water. The cells in the leaves are exposed to direct sunlight. Energy from the sunlight can be transferred from the plant cells to the water causing it to evaporate. This causes the plant cells to cool down and prevents direct sunlight from damaging the delicate cells.
The cells in a plant absorb water via osmosis and swell up. This results in a build-up of pressure called turgor pressure and the cells are said to be turgid. The cell wall surrounding all plant cells is made up of tough inelastic cellulose which stops the cells from swelling up too much. Turgid cells are firm and give the plant support. If the cells lose too much water, they shrink and become flaccid and the plant becomes soft and has less support. The stem no longer remains upright and the leaves wilt.
Movement of Minerals:
The water transported upwards from the roots to the leaves also contains dissolved mineral salts which are used to produce a variety of substances such as proteins in the plant.