What was done
The authors grew well watered and fertilized tomato [Solanum lycopersicum (formerly Lycopersicon esculentum) L. cv. Momotarou] seedlings for two weeks at two different levels of irrigation-water salinity (0 or 100 mM NaCl) in 3-L pots inside the greenhouse of Hiroshima University, Japan, at atmospheric CO2 concentrations of either 370 or 1000 ppm, while measuring various plant properties and physiological responses.

What was learned
Takagi et al. report that "salt-stress treatment severely decreased whole-plant biomass," as well as "leaf photosynthesis and transport of carbon assimilates," but that "the impact of stress on these activities was alleviated under elevated CO2 concentration." This alleviation, as they describe it, "was promoted when sink activity relative to source activity was higher," which they say was "probably owing to improvement of oxidative stress," due "at least partially to the higher constitutive antioxidant enzymes' activities," as well as improved water status "through stomatal closure at high CO2 concentration."

What it means
The seven scientists state that their study "corroborates earlier reports that the interaction between salinity stress and CO2 concentration result[s] in the alleviative effect of elevated CO2 on the negative effects of salinity on plant growth," for which conclusion much additional evidence is archived under the heading of Salinity (Effects on Plants) in our Subject Index. Hence, we have yet another indication of the ability of earth's plants to function ever more robustly and to successfully overcome various environmental challenges as the air's CO2 content continues to climb ever higher.