Seasonal and diurnal gas exchange differences in ozone-sensitive common milkweed ( Asclepias syriaca L.) in relation to ozone uptake

• Published in: Environmental pollution (1987) 2008-03, Vol.152 (2), p.403-415
• Main Authors: Bergweiler, Chris, Manning, William J., Chevone, Boris I.
• Format: Article
• Language: English
• Subjects: air pollution; Animal, plant and microbial ecology; Applied ecology; Asclepias - growth & development; Asclepias - metabolism; Asclepias syriaca; Biological and medical sciences; Carbon Dioxide - metabolism; Circadian Rhythm; Dehydration; diurnal variation; Ecotoxicology, biological effects of pollution; Environmental Monitoring - methods; Exposure indices; Fundamental and applied biological sciences. Psychology; gas exchange; General aspects; General aspects. Techniques; indicator species; Long-range transport; Methods and techniques (sampling, tagging, trapping, modelling...); Models, Biological; New England; Oxidants, Photochemical - toxicity; ozone; Ozone - toxicity; Ozone flux modeling; Ozone uptake; photosynthesis; physiological response; plant damage; Plant Leaves; Plant Transpiration; seasonal variation; Seasons; soil water regimes; Southern New England; Stomatal conductance
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2007.06.019

Stomatal conductance and net photosynthesis of common milkweed ( Asclepias syriaca L.) plants in two different soil moisture regimes were directly quantified and subsequently modeled over an entire growing season. Direct measurements captured the dynamic response of stomatal conductance to changing environmental conditions throughout the day, as well as declining gas exchange and carbon assimilation throughout the growth period beyond an early summer maximum. This phenomenon was observed in plants grown both with and without supplemental soil moisture, the latter of which should theoretically mitigate against harmful physiological effects caused by exposure to ozone. Seasonally declining rates of stomatal conductance were found to be substantial and incorporated into models, making them less susceptible to the overestimations of effective exposure that are an inherent source of error in ozone exposure indices. The species-specific evidence presented here supports the integration of dynamic physiological processes into flux-based modeling approaches for the prediction of ozone injury in vegetation. Temporal variation in physiological processes underlying diurnal and seasonal ozone uptake are described for a key ozone bioindicator species of North America.