Leaf Transpiration Efficiency in Four Corn Cultivars Grown at Elevated Carbon Dioxide

High leaf transpiration efficiency (TE) occurs in some cultivars of corn ( Zea mays L.) and could be a useful trait to improve yield under water deficits. The CO 2 concentration in the atmosphere continues to increase rapidly, and it is not certain that cultivar differences in leaf TE occurring at the current CO 2 concentration would still occur at elevated CO 2 . Two cultivars of sweet corn with high leaf TE and two with low TE were grown for two seasons in plots with free‐air CO 2 enrichment systems to determine whether elevated CO 2 altered the ranking of the cultivars in leaf TE. Measurements were also made at ambient CO 2 2 h and 5 d after termination of the CO 2 application. The results indicated that growth at 1.4 times the current CO 2 concentration resulted in one cultivar having about 25% higher leaf TE than the other three cultivars, which had similar values of TE. The changed ranking of one cultivar was a result of growth at elevated CO 2 and not the elevated measurement concentration. Thus, in one cultivar, the high leaf TE trait was stable across growth CO 2 conditions, but in another cultivar, the high TE trait was no longer evident when the plants were grown at elevated CO 2 . Screening of corn genotypes for high leaf TE at projected future CO 2 concentrations may be more efficiently accomplished at those concentrations.