Leaf–water relations and ion concentrations of the halophyte Atriplex hortensis in response to salinity and water stress

The impact of salinity and water stress was analyzed in the xero-halophyte Atriplex hortensis using two varieties: green orach (A. hortensis var. purpurea) and red orach (A. hortensis var. rubra). A. hortensis L. is a C3 species well adapted to salt and drought conditions. To collect information on the physiological impact of different salt and water deficit levels on their water stress resistance, plants were exposed for 3 months to solution containing four levels of NaCl or to water stress regimes including four levels of field capacity. Osmotic potential at zero turgor Ψs0, osmotic potential at full turgor (Ψs100), relative water content (RWC), ion concentration (Na+, K+, Ca2+, Mg2+, and Cl−), and malondialdehyde (MDA) were determined at the end of the treatment. The salinity and water stress induced a decrease in Ψs100, Ψs0, and RWC in both varieties, recorded changes being higher in plants of red variety than those of green variety. Both varieties specifically accumulated Na+ in response to drought and salt stress, suggesting that this element could play a physiological role in the stress response of this xero-halophyte species. In contrast, the presence of NaCl and water stress induced a decrease in K+, Ca2+, and Mg2+ concentration in both varieties. Salinity clearly induced an increase in Cl– concentration in all tissues, but water stress had no impact on this parameter. MDA concentration increased in response to water stress and exogenous NaCl. Based on these findings the more drought-tolerant red orach may be grown in water-limiting soils.