What was done
The authors grew spring wheat for an entire growing season in pots in open-top chambers at two CO2 concentrations (ambient and ambient plus 320 ppm), two O3 (ozone) concentrations (ambient and 1.5-times ambient), and two levels of watering (well-watered and only half the irrigation volume as that supplied to the well-watered plants), after which they measured a number of parameters related to plant growth.

What was learned
In the words of the authors, "CO2-enrichment resulted in an increase in tillering, tiller dry weight, ear number, ear dry weight, plant height, leaf area, and the number of leaves produced per plant."  Furthermore, they say that "no interactive effects of elevated CO2 with soil water deficit and/or O3 were detectable."

What it means
These findings suggest, again in the words of the authors, that "elevated CO2 reduces the negative effects of environmental constraints on plant growth," and that it does so "in an additive manner."  Just think how great it would be to be able to do that globally: reduce the negative effects of environmental constraints on plant growth.  Perhaps that should be our mantra: Free the Biosphere! Let the air's CO2 content rise.