Elevated carbon dioxide ameliorates the effects of ozone on photosynthesis and growth: species respond similarly regardless of photosynthetic pathway or plant functional group

Abstract

Due to their different physiological effects, elevated carbon dioxide and elevated ozone might have interactive impacts on plants, and differentially so on plants differing in photosynthetic pathway and growth rate. To test several hypotheses related to these issues, we examined the physiological, morphological and growth responses of six perennial species grown at various atmospheric concentrations of carbon dioxide and ozone. The species involved (two C $ trees : Populus tremuloides Michx., Quercus rubra L. ; two C $ grasses : Agropyron smithii Rybd., Koeleria cristata L. ; two C % grasses : Bouteloua curtipendula Michx., Schizachyrium scoparium Michx.) differed in growth form, stomatal conductance and photosynthetic pathway. In situ photosynthesis, relative growth rate () and its determinants (leaf area ratio, specific leaf area, leaf weight ratio and root weight ratio) were determined via sequential harvests of seedlings that were grown in all combinations of 366 or 672 µmol mol −" CO # and 3 or 95 nmol mol −" O $ over a 101-d period. Elevated CO # had minimal effect on either photosynthesis or . By contrast,  for all six species was lower in high O $ concentrations at ambient CO # , significantly so in A. smithii and P. tremuloides. Five of the six species also exhibited reductions in in situ photosynthesis at ambient CO # in high-O $ -grown compared with low-O $ -grown plants. For all species, these O $ -induced reductions in  and photosynthesis were absent in the elevated CO # environment. Root weight ratio was significantly reduced by elevated O $ in A. smithii and P. tremuloides in ambient but not elevated CO # . Species with high stomatal conductance were the most susceptible to oxidant injury, while those with low stomatal conductance, such as the C % species and Q. rubra, were not as detrimentally affected by O $ . Elevated levels of CO # will reduce stomatal conductance and O $ uptake, and might therefore reduce the potential for oxidant damage. However, there was a stronger relationship of the percent reduction in whole-plant mass due to O $ , related to the ratio of photosynthesis to stomatal conductance. In general, results of this study of six functionally diverse plant species suggest that O $ pollution effects on carbon balance and growth are likely to be ameliorated by elevated concentrations of atmospheric CO # .

Leaf injury characteristics of grassland species exposed to ozone in relation to soil moisture condition and vapour pressure deficit

“…A direct relationship between g s and the reduction in final plant mass due to high O $ has been observed (Volin et al, 1998). In those species in which reduced irrigation caused a reduction in both Ψ and g s , such as T. repens, T. pratense, T. flavescens and B. erectus (Table 5), the extent of injury was reduced in the dry treatment (Fig.…”

Characterization of an urban-rural CO 2 /temperature gradient and associated changes in initial plant productivity during secondary succession

“…"Codered") ozone days (approximately 10 over a 6 month period), argue against it being a significant confounding factor. It is possible that the prevailing ozone concentration increased the responsiveness to elevated [CO 2 ] (Volin et al 1998). However, the ozone levels reported here are representative of large areas of eastern North America (Krupa and Manning 1988;Krupa and Kickert 1997).…”

Elevated concentrations of atmospheric CO2 protect against and compensate for O3 damage to photosynthetic tissues of field‐grown wheat

“…In combination, ozone damage to photosynthetic tissues is ameliorated by elevated [CO # ], and recent studies have examined the mechanisms behind this interaction (Kramer et al, 1991 ;Polle et al, 1993 ;McKee et al, 1995McKee et al, , 1997bRao et al, 1995 ;Booker et al, 1997 ;Volin et al, 1998 ;Wieser et al, 1998). In controlled-environment studies, in which spring wheat was exposed to chronically elevated concentrations of CO # and\or O $ , the effect of elevated [O $ ] on photosynthesis resulted mainly from a loss of Rubisco activity (McKee et al, 1995(McKee et al, , 1997b.…”