Interaction of CO2 enrichment and drought on growth, water use, and yield of broad bean (Vicia faba)

Broad bean (Vicia faba cv. Lincan II) were grown in pots at two CO2 concentrations (350 and 700 parts per million by volume (ppmv)) and three soil water levels (80, 60 and 40% field water capacity) in field open-top chambers (OTCf). Water deficit reduced plant shoot dry weight, bean yield, and water use efficiency (WUE) by over 40, 30, and 15%, respectively, with higher relative reduction under elevated CO2. High CO2 significantly increased leaf photosynthesis, plant growth, bean yield and WUE. The increase is significant only at sufficient water supply. Both CO2 enrichment and water deficit influenced bean yield mainly through bean number. Harvest index was increased by both high CO2 and drought. There were significant interactions between CO2 enrichment and soil water deficit on plant growth and yield. On the basis of above results, it is concluded that the effects of CO2 enrichment on plants depend on soil water status, and the negative effects induced by drought will be relatively more serious in the future at increased CO2 concentrations. (C) 2000 Elsevier Science B.V. All rights reserved.