Ozone exposure causes a decoupling of conductance and photosynthesis: implications for the Ball-Berry stomatal conductance model

Abstract

Industrialization has significantly altered atmospheric chemistry by increasing concentrations of chemicals such as nitrogen oxides (NO( x )) and volatile organic carbon, which react in the presence of sunlight to produce tropospheric ozone (O(3)). Ozone is a powerful oxidant that causes both visual and physiological damage to plants, impairing the ability of the plant to control processes like photosynthesis and transpiration. Damage to photosynthesis and stomatal conductance does not always occur at the same rate, which generates a problem when using the Ball-Berry model to predict stomatal conductance because the calculations directly rely on photosynthesis rates. The goals of this work were to develop a modeling framework to modify Ball-Berry stomatal conductance predictions independently of photosynthesis and to test the framework using experimental data. After exposure to elevated O(3) in open-top chambers, photosynthesis and stomatal conductance in tulip poplar changed at different rates through time. We were able to accurately model observed photosynthetic and stomatal conductance responses to chronic O(3) exposure in a Ball-Berry framework by adjusting stomatal conductance in addition to photosynthesis. This led to a significant improvement in the modeled ability to predict both photosynthesis and stomatal conductance responses to O(3).

Impacts of elevated ozone on growth and photosynthesis of Metasequoia glyptostroboides Hu et Cheng

“…The O 3 exposure induces an uncoupling of photosynthesis and stomatal conductance, as previously observed in three native tree species from China (Ailanthus altissima, Fraxinus chinensis and Platanus orientalis) [35]. Lombardozzi et al [19] reported that the typical coupling of stomatal conductance and photosynthesis does not always hold under high O 3 conditions, because O 3 can directly affect the function of stomatal cells so that g s no longer responds dynamically to changes in C i and the rate of carboxylation due to enzyme and membrane damage. Unchanged g s with increased C i in the second growing season, as observed in this study, indicated that the decrease in photosynthesis was independent of g s [15,36].…”

“…Reductions in A sat have been attributed to decreases in primary carboxylation enzyme Rubisco transcript levels, antioxidant contents and enzyme activity rather than changes in g s [17,18]. A recent study suggests that elevated O 3 induces faster rates of change in photosynthesis rate compared to g s because of the significant decrease in the maximum activity of Rubisco (V c,max ) and maximum electron transport rate (J max ), i.e., O 3 reduces the biochemical capacity to fix CO 2 [19].…”

Particulate matter air pollution may offset ozone damage to global crop production

“…Ozone has a negative impact on crop production by reducing gas exchange and inflicting phytotoxic damage on plant tissues (Lombardozzi et al, 2012;Sitch et al, 2007;Wilkinson et al, 2011). The crop-specific relationships between surface ozone concentration and crop yield loss have been established using several exposure metrics.…”

Pigmentos fotosintéticos y conductancia estomática en ecotipos de copoazú (Theobroma grandi orum Willd. Ex. Spreng K. Schum.).

“…En este sentido se ha sugerido que existe una estrecha correlación entre la conductancia y la fotosíntesis en un amplio rango de condiciones ambientales, ya que los estomas responden a los cambios ambientales como la radiación y el déficit de presión de vapor (Lombardozzi et al, 2012).…”