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Salinity Stress in Barley
Perez-Lopez, U., Robredo, A., Lacuestra, M., Sgherri, C., Munoz-Rueda, A., Navari-Izzo, F. and Mena-Petite, A. 2009. The oxidative stress caused by salinity in two barley cultivars is mitigated by elevated CO2. Physiologia Plantarum 135: 29-42.

Soil salinity, to quote the authors, "is one of the major environmental constraints limiting plant productivity and distribution [and] affects 19.5% of the world's irrigated area and also occurs on non-irrigated croplands and rangelands."

What was done
Perez-Lopez et al. grew two barley (Hordeum vulgare L.) cultivars, Alpha and Iranis, within controlled-environment growth chambers at either ambient (350 ppm) or elevated (700 ppm) atmospheric CO2 concentrations in a 3:1 perlite:vermiculite mixture that was watered with Hoagland's solution every two days (until the first leaf was completely expanded at 14 days), after which a salinity treatment was administered by adding 0, 80, 160 or 240 mM NaCl to the Hoagland's solution every two days for 14 more days. Then, after a total of 28 days, the primary leaf of each barley plant was harvested and assessed for a number of biochemical properties.

What was learned
The seven scientists report that in the various ambient-air salinity treatments, the deleterious effects of reactive oxygen species (ROS) on barley leaves were made apparent through ion leakage and increases in thiobarbituric acid reactive substances (TBARS), which rose ever higher as salt concentrations rose ever higher. "On the other hand," as they continue, "when [the] salinity treatment was imposed under elevated CO2 conditions, lower solute leakage and TBARS levels were observed, suggesting that the oxidative stress caused by salinity was lower."

What it means
In interpreting their findings, Perez-Lopez et al. say "it is concluded that elevated CO2 protects barley cultivars from oxidative stress," noting that "the relief of oxidative stress damage observed in our barley leaves grown under [a] CO2 enriched atmosphere has also been observed in alfalfa (Sgherri et al., 1998), pine (Vu et al., 1999) and oak (Schwanz and Polle, 2001)." Hence, it would appear that the ongoing rise in the air's CO2 content may help a wide variety of earth's plants to better cope with the many serious problems caused by high soil salinity.

Schwanz, P. and Polle, A. 2001. Differential stress responses of antioxidative systems to drought in pendunculate oak (Quercus robur) and maritime pine (Pinus pinaster) grown under high CO2 concentrations. Journal of Experimental Botany 52: 133-143.

Sgherri, C., Quartacci, M., Menconi, M., Raschi, A. and Navari-Izzo, F. 1998. Interactions between drought and elevated CO2 on alfalfa plants. Journal of Plant Physiology 152: 118-124.

Vu, J.C., Gesch, R., Allen, L.H., Boote, K. and Bowes, G. 1999. CO2 enrichment delays a rapid, drought induced decrease in Rubisco small subunit transcript abundance. Journal of Plant Physiology 155: 139-142.

Reviewed 4 March 2009