CBSE Class 10 Science 2020 · Paper 31/C/3 · Question 19

Transpiration is the loss of water in the form of vapour from the aerial parts of a plant, mainly through the stomata of the leaves. Water brought to the leaf by the xylem evaporates from the leaf cells into the air spaces and diffuses out through the open stomata, whose opening is controlled by the guard cells. The water lost is replaced from the xylem, so a suction, the transpiration pull, draws a continuous column of water up from the roots. How it helps: (1) the transpiration pull keeps water rising from the roots, so the cells stay turgid and the plant remains fresh; (2) minerals dissolved in this water reach the leaves and other parts, and the leaves get water for photosynthesis, keeping the plant healthy; (3) evaporation cools the leaves and helps regulate their temperature.