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Effects of Elevated CO2 on Salt Tolerance of Barley
Perez-Lopez, U., Robredo, A., Lacuesta, M., Munoz-Rueda, A. and Mena-Petite, A. 2010. Atmospheric CO2 concentration influences the contributions of osmolyte accumulation and cell wall elasticity to salt tolerance in barley cultivars. Journal of Plant Physiology 167: 15-22.

The authors write that the buildup of salt in soils "can inhibit the growth of valuable crops such as barley," due to the fact that the "osmotic stress caused by low water potential in salinized soils reduces the availability of water for uptake by plants." This stress, however, may be mitigated by plants that actively decrease their osmotic potential via a phenomenon known as osmotic adjustment; but the processes involved in this adjustment require extra energy that often leads to a reduction in plant growth, which penalty or tax is sometimes referred to as "the cost of salt tolerance."

What was done
Perez-Lopez et al. grew two different barley (Hordeum vulgare L.) cultivars under well watered and fertilized conditions in pots placed within controlled-environment chambers they maintained at atmospheric CO2 concentrations of either 350 or 700 ppm for a period of 28 days. During this time, midday leaf water potential, osmotic potential, osmotic potential at full turgor, dehydration and osmotic adjustment were routinely measured, after which the primary leaf of each plant was harvested and assessed for concentrations of various minerals and organic compounds.

What was learned
The five researchers report that "elevated CO2 permitted plant metabolism to be maintained at a better status under salt stress than did ambient CO2," noting that "growth was reduced more at ambient than at elevated CO2." They also found that "elevated CO2 widens the range of salt concentrations at which osmotic adjustment continues to be efficient by providing the greater supply of carbon and ATP [Adenosine-5'-triphosphate]," which is a multifunctional nucleotide that transports chemical energy within cells for metabolism and is, in their words, "needed to perform the energetically expensive salt tolerance mechanisms."

What it means
According to the Spanish scientists who conducted the work, their data suggest that "under future environmental conditions, barley species will be able to succeed in salinized areas in which growth is not currently possible." This phenomenon, quite obviously, should prove a great blessing to humanity.

Reviewed 7 April 2010