This review reports research on the control of O3 uptake in field grown trees by the stomata, addressing the following questions: How is O3 uptake influenced by environmental factors? Are there differences in O3 uptake within the canopy? To what extent do altitudinal changes in environmental parameters cause differences in O3 uptake? The review will mainly focus on conifers because only litte information is available on O3 uptake by deciduous trees and hardwoods.
