Topic 9

• Transpiration is the loss of water vapor from the stems and leaves of plants
• Light energy converts water in the leaves to vapor, which evaporates from the leaf via stomata
• New water is absorbed from the soil by the roots, creating a difference in pressure between the leaves (low) and roots (high)
• Water flows, via the xylem, along the pressure gradient to replace the water lost from leaves (transpiration stream)
• Stomata are pores on the underside of the leaf which facilitate gas exchange needed for photosynthesis
• Transpiration is affected by the level of photosynthesis since photosynthetic gas exchange requires stomata to be open
• Transpiration is the inevitable consequence of gas exchange in the leaf