What was done
Working out-of-doors at 35°59'N, 50°75'E, the authors grew two varieties (Okapi and Talaye) of canola (Brassica napus L.) plants over the 2008 and 2009 growing seasons beneath rigid frames covered with polyethylene plastic film in air maintained at ambient and elevated atmospheric CO2 concentrations of 400 and 900 ppm, at ambient and elevated levels of UV radiation, and under well-watered and deficit-watered conditions, during and after which periods they measured numerous plant properties.

What was learned
Tohidimoghadam et al. report that "water stress significantly decreased yield and yield components, oil yield, protein percentage, height, specific leaf area and the number of branches," but that elevated CO2 "increased the final yield, 1000-seed weight, oil percentage, oil yield, height, specific leaf area and number of branches," while UV radiation "decreased the yield, yield components, oil and protein percentages and growth parameters." They also note that "the highest seed weight was obtained from the 'Talaye' cultivar treated with compete irrigation and elevated CO2 and grown under sunlight radiation," while "the seed weights of both cultivars visibly decreased due to UV-B, UV-C and water stress under an ambient CO2 concentration."

What it means
The three Iranian researchers state that "an increase in UV exposure deceases plant growth and development," but that "elevated CO2 ameliorate(s) the adverse effects of UV radiation in the final yield, seed weight, oil percentage, oil yield, plant height, specific leaf area and number of branches per plant," concluding that an increase in the atmosphere's CO2 concentration "could improve yield, yield components and growth parameters for plants subjected to elevated levels of UV radiation."