What was done
The authors studied the long-term effects of atmospheric CO2 enrichment on water relations in three woody shrubs (Erica arborea L., Myrtus communis L., and Juniperus communis L.) growing near CO2-emitting springs in Pisa, Italy.  At different distances from the CO2 springs, physiological measurements were made on shrubs that had been experiencing atmospheric CO2 concentrations of approximately 360 and 700 ppm for their entire lifetimes.

What was learned
The effects of elevated CO2 on plant water relations varied over a 12-month monitoring period based on shrub species and time of measurement (seasonal differences).  However, one common trend was evident; elevated CO2 increased the leaf turgor pressure of all shrubs, particularly during the warmer summer months.

What it means
As the air's CO2 content rises, these Mediterranean shrubs will likely exhibit species-specific and season-specific changes in water relations.  Nonetheless, all three shrubs will likely exhibit increases in turgor pressure, which phenomenon should allow them to better deal with stresses induced by drought.  Thus, such plants will likely exhibit greater tissue water contents and withstand longer periods of reduced soil moisture before succumbing to wilt in a future world characterized by higher atmospheric CO2 concentrations.