Plants transpire the least when it is dark and there is lots of humidity. Photosynthesis does not occur without light and the humidity prevents water from diffusing out the leaf. RESULTS: [pick] DISCUSSION: Our class data showed that the transpiration pull was the second highest in humidity and in the dark. This data is incorrect, in this given condition because in plants, transpiration is controlled by water potential.
This change in water potential in leaves causes a gradient by which water can be moved upward. When the water potential of the air was increased by the humidifier and plastic covering, less water evaporated from the leaves, decreasing the water potential radiant between the root and stem, in turn decreasing the transpiration pull. These conditions should have shown little or no transpiring.
High humidity and light showed the least transpiration although photosynthesis is taking place and the stomata are open for water to diffuse out from, making it in actuality the second highest transpiration pull. Had the most water loss when my plant was placed under light and low humidity. When the air outside is drier the transpiration pull increases. The light allows for photosynthesis to occur in which the stomata open up to let in carbon dioxide.