Ozone exposure affects leaf wettability and tree water balance

Area of Science:

• Environmental Science
• Plant Physiology
• Atmospheric Chemistry

Background:

• Growing-season background ozone (O3) concentrations are known to affect plant health, but their specific impacts on leaf cuticles and water loss are not fully understood.
• Ozone is a significant air pollutant with potential to influence plant physiological processes and ecosystem dynamics.

Purpose of the Study:

• To investigate the effects of varying ozone (O3) concentrations on leaf wettability and foliar water loss in two poplar species (Populus nigra, P. euramericana) and one conifer (Pseudotsuga menziesii).
• To determine species-specific responses to ozone exposure relevant to urban and montane environments.

Main Methods:

• Controlled fumigation experiments were conducted using three ozone (O3) regimes: control (approx. 1 ppbv), urban (13-41 ppbv), and montane (30-45 ppbv).
• Leaf wettability (droplet contact angles) and foliar water loss rates were measured.
• Photosynthetic biomass, leaf production, leaf abscission, and visible foliar injury were assessed.

Main Results:

• Urban ozone exposure delayed changes in leaf wettability in Populus species and decreased it in P. menziesii.
• Ozone exposure increased foliar water loss and minimal conductance in P. euramericana, but not in P. nigra or P. menziesii.
• Both Populus species exhibited reduced photosynthetic biomass due to fewer new leaves, premature leaf abscission, and, in P. euramericana, decreased leaf size, often preceded by ozone-induced foliar injury.

Conclusions:

• Ozone concentrations typical during the growing season can increase water loss in Populus saplings, though this may be counteracted by reduced foliar biomass.
• Plant responses to ozone exposure are highly species-specific, highlighting the need for differential assessments in environmental impact studies.