Interactions between Elevated CO2 and Water Stress in Two Winter Wheat Cultivars Differing in Drought Resistance

Abstract

Two winter wheat varieties (Alba, cultivated in Poland and usually having high biomass production, and the Hungarian variety Martonvasari 15, which has better drought tolerance) were grown in two phytotron chambers at 375and 700 μmol mol - 1 air CO 2 concentration with three different levels of water supply, to evaluate the interactive effects of elevated CO 2 concentration and drought stress on yield components and leaf photosynthetic activity. Elevated CO 2 concentration had positive effects on the development of the plants and decreased the negative effects of drought, while the development of the more drought-tolerant variety Martonvasari 15 was hindered by elevated CO 2 concentration at high water supplies. Grain yield was mainly affected by drought. The negative effects of water stress were partially compensated by elevated CO 2 concentration. Gas exchange changed in different ways, depending of the duration of the treatments: low water supplies decreased the net photosynthesis, transpiration and stomatal conductivity of both varieties, while elevated CO 2 concentration decreased them in the beginning then increased them by the 10th week of treatment.