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Transpiration - Water Movement through Plants: Transpiration - Overview and Objectives Tracy M. Sterling Department of Entomology, Plant Pathology and Weed Science at New Mexico State University, USA Lesson Navigation Tips: - Click on 'Animations' button found to the left in order to view the animation which supplements this lesson. You can also click on the animation icon within the text. - Click once on figures to see enlarged versions. - Click once on words in color to bring up their definitions. Overview Transpiration is the loss of water from a plant in the form of water vapor. Water is absorbed by roots from the soil and transported as a liquid to the leaves via xylem. In the leaves, small pores allow water to escape as a vapor and CO2 to enter the leaf for photosynthesis. Of all the water absorbed by plants, less than 5% remains in the plant for growth and storage following growth. This lesson will explain why plants lose so much water, the path water takes through plants, how plants might control for too much water loss to avoid stress conditions, and how the environment plays a role in water loss from plants. Objectives: At the completion of this lesson, students will be able to: Define transpiration and explain why it occurs in plants. Follow the pathway that water takes through plants from root uptake to evaporation at leaf cell surfaces. Describe how the driving force for water movement and any resistances to its flow through the plant are the two major components controlling rates of transpiration. Describe how environmental conditions alter rates of transpiration. Explain how the plant is able to alter rates of transpiration. Development of this lesson was supported in part by the Cooperative State Research, Education, & Extension Service, U.S. Dept of Agriculture under Agreement Number PX2003-06237 administered by Cornell University, Virginia Tech and the American Distance Education Consortium (ADEC) and in part by the New Mexico and Nebraska Agricultural Experiment Stations. Any opinions,findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.