Interaction of elevated CO2and O3on growth, photosynthesis and respiration of three perennial species grown in low and high nitrogen

Publisher Website
Google Scholar
Abstract
Seedlings of three species native to central North America, a C3tree,Populus tremuloidesMichx., a C3grass,Agropyron smithiiRybd., and a C4grass,Bouteloua curtipendulaMichx., were grown in all eight combinations of two levels each of CO2, O3and nitrogen (N) for 58 days in a controlled environment. Treatment levels consisted of 360 or 674 μmol mol‐1CO2, 3 or 92 nmol mol‐1O3, and 0.5 or 6.0 mMN. In situ photosynthesis and relative growth rate (RGR) and its determinants were obtained at each of three sequential harvests, and leaf dark respiration was measured at the second and third harvests. In all three species, plants grown in high N had significantly greater whole‐plant mass, RGR and photosynthesis than plants grown in low N. Within a N treatment, elevated CO2did not significantly enhance any of these parameters nor did it affect leaf respiration. However, plants of all three species grown in elevated CO2had lower stomatal conductance compared to ambient CO2‐exposed plants. Seedlings ofP. tremuloides(in both N treatments) andB. curtipendula(in high N) had significant ozone‐induced reductions in whole‐plant mass and RGR in ambient but not under elevated CO2.This negative O3impact on RGR in ambient CO2was related to increased leaf dark respiration, decreased photosynthesis and/or decreased leaf area ratio, none of which were noted in high O3treatments in the elevated CO2environment. In contrast,A. smithiiwas marginally negatively affected by high O3.