Transpiration and Leaf Resistance

Transpiration and Leaf Resistance
By: Bernina Berber

Introduction Transpiration is a part of the water cycle process, and it is the loss of water vapor from parts of the plants. It is a process similar to evaporation. Evaporation and diffusion cause the plant tissue to have negative water potential. If you were to compare transpiration it would be like saying it is close to sweating (but in plants), especially in leaves but also in stems, flowers and roots. Stomata are dots with openings on top of the leaves surfaces, which in many plants have numerous on the undersides of the foliage. The stomas are boarded by guard cells that open and close the pore. Leaf transpiration happens through stomata, it is considered as a necessary need associated with the opening of the stomata to allow the diffusion of carbon dioxide gas from the air for photosynthesis. Transpiration is very important for plants because it cools them and enables the mass flow of mineral nutrients and water from roots and shoots. The amount of water vapor within the plant tissue, air humidity, and air temperature all play a roll in the rate of transpiration. The rate of transpiration can be measured using the mass of water lost per unit area of leaf tissue relative to time. When you take a leaf from a plant it is obvious that water is lost from the tissue, however it has no source of water to compensate for its negative water potential, which keeps increasing. When cuticles are waxy that helps the leaf to slow the loss of water vapor. High cuticular pathway resistance is indicated when there is a low rate of water; on the other hand this means that the leaf has a high resistance to water loss. In this lab we were suppose to determine the rate of transpiration from a cut segment of citrus leaves. We are to test their resistance to the loss of water vapor (affected by the thickness of varying cuticles depending on the species of plant used). We determined the rate of transpiration by finding the