text: The four researchers report that their data indicated that for both maize and grain sorghum, there was a "maintenance of relatively high canopy photosynthetic rates in the face of decreased transpiration rates resulted in enhanced water use efficiency when these plants were grown at elevated CO 2 of 720 ppm, but not at 360 ppm." And as a result, they demonstrated that "both plants maintained growth better at double-ambient CO 2 than their counterparts at ambient CO 2 in the presence of drought," such that reductions in total above-ground biomass due to drought were 42% for maize and 36% for sorghum at ambient CO 2 , but only 18% for maize and 14% for sorghum at double-ambient CO 2 .