Volin John C, Reich Peter B, Givnish Thomas J
Department of Forestry, University of Wisconsin, 1630 Linden Drive, Madison, WI 53706, USA.
To whom correspondence should be addressed.
New Phytol. 1998 Feb;138(2):315-325. doi: 10.1046/j.1469-8137.1998.00100.x.
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 (RGR) 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 RGR. By contrast, RGR 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 RGR 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 .
由于二氧化碳浓度升高和臭氧浓度升高具有不同的生理效应，它们可能会对植物产生交互影响，而且对光合途径和生长速率不同的植物影响也有差异。为了验证与这些问题相关的几个假设，我们研究了六种多年生植物在不同大气二氧化碳和臭氧浓度下生长时的生理、形态和生长反应。所涉及的物种（两种C₃树木：颤杨Populus tremuloides Michx.、红栎Quercus rubra L.；两种C₃草本植物：史密斯冰草Agropyron smithii Rybd.、穗状三毛草Koeleria cristata L.；两种C₄草本植物：短穗布顿草Bouteloua curtipendula Michx.、糙毛裂稃草Schizachyrium scoparium Michx.）在生长形态、气孔导度和光合途径方面存在差异。通过在101天的时间里对在366或672 μmol mol⁻¹ CO₂以及3或95 nmol mol⁻¹ O₃的所有组合条件下生长的幼苗进行连续收获，测定原位光合作用、相对生长速率（RGR）及其决定因素（叶面积比、比叶面积、叶重比和根重比）。二氧化碳浓度升高对光合作用或相对生长速率的影响最小。相比之下，在环境二氧化碳浓度下，所有六个物种在高臭氧浓度下的相对生长速率较低，在史密斯冰草和颤杨中尤为明显。与低臭氧浓度下生长的植物相比，六个物种中有五个在高臭氧浓度下生长的植物在环境二氧化碳浓度下原位光合作用也有所降低。对于所有物种来说，在二氧化碳浓度升高的环境中，这些由臭氧引起的相对生长速率和光合作用的降低并不存在。在环境二氧化碳但不是升高的二氧化碳条件下，史密斯冰草和颤杨中臭氧浓度升高显著降低了根重比。气孔导度高的物种最易受到氧化损伤，而气孔导度低的物种，如C₄物种和红栎，受臭氧的不利影响较小。二氧化碳浓度升高会降低气孔导度和对臭氧的吸收，因此可能会降低氧化损伤的可能性。然而，由于臭氧导致的整株植物质量减少百分比与光合作用与气孔导度的比值之间存在更强的关系。总体而言，对六种功能多样的植物物种的这项研究结果表明，大气二氧化碳浓度升高可能会减轻臭氧污染对碳平衡和生长的影响。
