Photosynthesis in an open field for exotic versus native vines of the southeastern United States

The potential importance of leaf gas exchange to the prolific growth characteristics of the exotic vines Pueraria lobata and Lonicera japonica versus the native vines Rhus radicans, Parthenocissus quinquefolia, Vitis vulpina, and Clematis virginiana was evaluated. Under high irradiance and low leaf-air water vapor pressure difference, photosynthesis was similar (23 – 27 μmol∙m−2∙s−1) among species with the exception of R. radicans (16 μmol∙m−2∙s−1). Conductance and transpiration were greater in Pueraria lobata than in the other species. When the leaf-air vapor pressure difference was high (4.0 kPa) photosynthesis in the exotic vines decreased more than in several of the native species. Photosynthesis in L. japonica and Parthenocissus quinquefolia, and to a lesser extent in Pueraria lobata, was reduced by high vapor pressure differences even though internal CO2 partial pressures remained relatively high, suggesting a nonstomatal reduction of photosynthetic capacity. Thus, the highly prolific growth typical of the exotic vines may not be attributable to greater steady-state photosynthesis.