Characterization of ambient ozone uptake and development of foliar injury models from a plant physiological ecology perspective.

摘要

A biologically-based secondary ambient air quality standard for vegetation in the U.S. is presently lacking. Analyses sensitive to the physiological conductivity of exposed plants as well as atmospheric and soil conditions were used here to predict the signature response of plants to ozone, foliar injury. Bel-W3 tobacco (Nicotiana tabacum L. cv. Bel-W3) was used as an acute-response model while Asclepias syriaca L. was used as a chronic-response model to identify important controlling factors involved in foliar injury response to ambient ozone. Temperature, RH, PAR, wind velocity, soil moisture, soil matric potential, and vapor pressure deficit were investigated relative to their influence on injury development during simultaneous exposure to ozone. Several important factors were found to lead to overestimation of vegetation exposure to ambient ozone. These included use of a standard ozone measurement height, soil moisture deficits, asynchrony between diurnal stomatal conductance and peak ozone concentration, episodic exposures to elevated ozone concentrations during late-day weak sunlight (PAR 500), and seasonal decline of gas exchange and ozone uptake in herbaceous plants. These results indicate the need for refinement of current indices to protect vegetation, which, if based solely on ozone concentration, e.g. AOT40, SUM06, W126, will continue to lead to overestimation of ozone exposure.