Students in the biology class section taught by Brad Taylor, recently conducted a lab experiment in which they tested plants for their rate of transpiration.


Water is transported in plants, from the roots to the leaves, following a decreasing water potential gradient. Transpiration, or loss of water from the leaves, helps to create a lower osmotic potential in the leaf. The resulting transpirational pull is responsible for the movement of water from the xylem to the mesophyll cells into the air spaces in the leaves. The rate of evaporation of water from the air spaces of the leaf to the outside air depends on the water potential gradient between the leaf and the outside air.


Various environmental factors, including those conditions which directly influence the opening and closing of the stomata, will affect a plant’s transpiration rate. This experiment was designed to measure transpiration rates under different conditions of light, humidity, temperature and air movement.


‘The data will be collected by measuring pressure changes as the plant takes up water into the stem,” Taylor said. “This lab will help students to determine the effect of light intensity, humidity, wind and temperature on the rate of transpiration of a plant cutting.”