Document: DAV-3-34-34

Photosynthetic responses of three vine species to elevated CO₂ in a piedmont North Carolina forest understory.

MYERS, D.A.* and R.B.THOMAS

West Virginia University, Morgantown, WV USA 26506-6057 ¹

Abstract:
Photosynthetic capacity of wild grape (Vitis rotundifolia Michaux), Virginia creeper (Parthenocissus quinqefolia (L.) Planchon), and Japanese honeysuckle (Lonicera japonica Thunberg) growing near the forest floor was measured using open flow gas exchange and simultaneous chlorophyll fluorescence analysis at the BNL/Duke FACTS-I Free Air CO₂ Enrichment site. Wild grape and Virginia creeper are native to the piedmont forest while Japanese honeysuckle is an invasive exotic. The relative enhancement of photosynthesis by elevated CO₂ in saturating light was 66 % and 51% for wild grape and Japanese honeysuckle, respectively, while photosynthesis of Virginia creeper was not significantly enhanced by CO₂. Elevated CO₂ had no effect on the maximum rate of carboxylation of Rubisco (V_cmax, from A-Ci data) in any species. The apparent quantum yield of photosynthesis was increased by CO₂ only in Japanese honeysuckle (46%). A flourimetric examination of excess light energy dissipation (NPQ) during sunfleck light levels was performed. Relatively high levels of NPQ were found in Virginia creeper but no effect of elevated CO₂ on NPQ was found. In Japanese honeysuckle, however, NPQ requirements when measured in elevated CO₂ were approximately 50% of that found for the two native species. The rate of electron transport (ETR) estimated from chlorophyll fluorescence was not affected by elevated CO₂ in shade light for any species. ETR was enhanced in high light by 34% for Japanese honeysuckle but high light decreased ETR by 40% for Virginia creeper. These results suggest that the invasive species, Japanese honeysuckle, growing in elevated CO₂ makes more efficient use of both shade light and sunflecks than do the native species, wild grape and Virginia creeper.

Keywords: vines, elevated CO2, gas exchange, flourescence, NPQ, ETR, FACE

This abstract is being presented at: 10:30 AM in session:
Poster Session #1: Light Relations.