Impact of elevated CO2on two contrasting wheat genotypes exposed to intermediate drought stress at anthesis

The objective of this experiment was to investigate the responses of contrasting wheat genotypes to drought stress under ambient and elevated CO(2)environments. At anthesis, the plants from each CO(2)levels were either exposed to progressive drought or well-watered at 95% of pot holding capacity. The results showed that for both genotypes, CO(2)elevation sensitized the plants' response to soil drying in terms of reduction of evapotranspiration. Drought significantly reducedtrans-zeatin (tZ) concentration in leaves, salicylic acid (SA) concentration in spikes, and physiological and yield-related traits. However, the concentration of abscisic acid (ABA) and other phytohormones was increased under drought, which coincided with an increase in the kernel abortion. Elevated CO(2)significantly increased photosynthetic rate, but had no significant effect on yield-related traits. Genotype L(3)possessed higher concentration of leaf tz, osmotic potential, and spike SA/ABA ratio under combined drought and elevated CO(2)as compared to genotype L-2. L(3)also had higher thousand kernel weight (TKW) and grain yield in comparison to L-2. The results indicate that elevated CO(2)is not necessarily increasing yield, and biophysiochemical traits in L(3)could be used as valuable selecting criteria to obtain higher TKW and grain yield in future drier and CO2-enriched environment.