Response of Two Old Field Perennials to Interactions of Co2 Enrichment and Drought Stress

Aster pilosus Willd. (aster, C3) and Andropogon virginicus L. (broomsedge, C4) were grown in growth chambers at 26/20 C day/night temperatures with a PPFD of 1,000 μmol s–1 m–2. Water was withheld for a 2‐wk drought period under three CO2 concentrations (approximately 380, 500, and 650 μl 1–1). There were significant effects of CO2 enrichment on aster so that drought stress did not occur in plants grown with CO2 enrichment. Non‐watered plants with CO2 enrichment had greater leaf water potentials, greater photosynthetic rates, and greater total dry wt than non‐watered plants grown at 380 μl 1–1 CO2. The response of broomsedge to drought was the same in all CO2 treatments and there was no significant interaction of CO2 enrichment and drought. The decreased severity of drought stress and the increased growth of aster with CO2 enrichment may increase its competitive ability during droughts, allowing it to persist for longer periods during succession in abandoned fields.