Impact of Precipitation and Water Availability on Plant Growth and Ecosystems

Plant leaves have small openings called stomata that can be adjusted to regulate the exchange of water vapor and CO₂ with the atmosphere. Plants not under water stress keep their stomata open for optimum CO₂ exchange. Under stress, however, plants close their stomata to restrict water loss. They also may allow their leaves to droop to reduce light absorption or they may shed leaves to reduce water loss. C4 plants have higher WUE than C3 plants. Higher atmospheric CO₂ levels will cause stomata to close slightly, increase WUE, and increase carbon gain for plants with limited water supply. Higher temperatures may lead to higher differences in water-vapor concentration inside and outside the stomata, however, and thereby lead to reduced WUE.

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