Introduction:

Among the adverse conditions of forest ecosystems, salinity and drought are the abiotic factors that largely modify the genetic and productive expression of species.

Objective:

To evaluate the effect of salinity and drought on the water regime and gas exchange of mesquite (Prosopis laevigata [Humb. & Bonpl. ex Willd.] M. C. Johnst.) in two semi-arid sites, Eco Camping and Bahía de Lobos, in southern Sonora, Mexico.

Materials and methods:

The water and osmotic potentials were determined in the root, stem and leaves of plants taken at random with similar morphological traits (height of 1.5 m and stem diameter of 0.15 m measured at 1.3 m). In addition, photosynthesis, transpiration and water-use efficiency were evaluated.

Results and discussion:

Water and osmotic potentials decreased significantly (P = 0.0043); the osmotic potential was the lowest in the three organs measured, forming a potential gradient, an aspect that explains the maintenance of transpiration in both conditions (salinity and drought). Photosynthesis did not vary significantly, but transpiration did. In both sites, water-use efficiency exceeded 6 μmol CO2/H2O; however, there was greater efficiency in the saline ecosystem due to the transpiration decrease.

Conclusion:

Mesquite has the ability to tolerate the stressful conditions of salinity and drought in southern Sonora, showing less impact in water relations and gas exchange in the salinity condition.