Effects of CO 2 Enrichment and Drought on Photosynthesis, Growth and Yield of an Old and a Modern Barley Cultivar

Susceptibility of crops to drought may change under atmospheric CO 2 enrichment. We tested the effects of CO 2 enrichment and drought on the older malting barley cultivar Golden Promise ( GP ) and the recent variety Bambina ( BA ). Hypothesizing that CO 2 enrichment mitigates the adverse effects of drought and that GP shows a stronger response to CO 2 enrichment than BA , plants of both cultivars were grown in climate chambers. Optimal and reduced watering levels and two CO 2 concentrations (380 and 550 ppm) were used to investigate photosynthetic parameters, growth and yield. In contrast to expectations, CO 2 increased total plant biomass by 34 % in the modern cultivar while the growth stimulation was not significant in GP . As a reaction to drought, BA showed reduced biomass under elevated CO 2 , which was not seen in GP . Grain yield and harvest index ( HI ) were negatively influenced by drought and increased by CO 2 enrichment. BA formed higher grain yield and had higher water‐use efficiency of grain yield and HI compared to GP . CO 2 fertilization compensated for the negative effect of drought on grain yield and HI , especially in GP . Stomatal conductance proved to be the gas exchange parameter most sensitive to drought. Photosynthetic rate of BA showed more pronounced reaction to drought compared to GP . Overall, BA turned out to respond more intense to changes in water supply and CO 2 enrichment than the older GP .