Growth and physiological effects of single and combined Cu, NaCl, and water stresses on Atriplex atacamensis and A. halimus

Halophyte species have been proposed as suitable candidates for the phytostabilization of metal enriched sites in arid and semiarid ecosystems, but co-occurring conditions, such as salinity and water stress, can affect plant growth and colonization. In this work, we determined the effect of single and combined copper (Cu), salt (NaCl), and water stress on growth and tolerance strategies used by two xerohalophyte species of the genus Atriplex: Chilean A. atacamensis and European A. halimus. Seedlings of both species were subjected to 5 and 10 u M Cu, 0.5% NaCl, and 7.85 mM polyethylene glycol 6000 (PEG) in hydroponic cultures to create single and combined stress treatments. A single Cu stressor decreased growth parameters of both species, with a higher effect on A. atacamensis. Copper accumulation was higher in roots, which can be related to an increase of root non-protein thiols (NPT). Single NaCl had no negative effects on growth but increased leaf sodium (Na). Single PEG decreased shoot growth, especially in A. halimus, but had no effect on GSH expression. A combination of Cu, NaCl, and PEG further decreased growth parameters, but did not decrease glutathione, proline, or non-protein thiol expression. Atriplex atacamensis and A. halimus are affected differently by combined stresses, but both species show an active tolerance response to the presented conditions.