Name___________________________ AP Biology: Plant Transpiration Lab Purpose: To determine how different environmental conditions can affect the rate of plant transpiration Background: Transpiration is the evaporation of water from plants. It occurs chiefly in the leaves while their stomata (tiny openings in the undersurface of a leaf) are open for the passage of CO2and O2during photosynthesis. Air that is not fully saturated with water vapor (100% relative humidity) will dry the surfaces of cells with which it comes in contact. So the photosynthesizing leaf loses substantial amount of water by evaporation. This transpired water must be replaced by the transport of more water from the soil to the leaves through the xylem of the roots and stem. Transpiration accounts for approximately 10% of all evaporating water on this planet. As leaves transpire, the outward flow of water lowers the pressure in the leaf, creating a vacuum that pulls water upward. This force is responsible for most of the water flow in plants, including lifting water to the tops of trees. Directions:For this lab, you will perform the experiment virtually and then analyze the data. Even though we are not actually performing the lab, you are still required to understand the purpose and procedure of the lab as if you actually performed the lab.