Impact of Salinity on Plant Growth, Photosynthesis, Cell Wall Elasticity and Osmotic Adjustment in Damask Rose

Damask rose can survive soil salinity levels up to 150 mM NaCl despite reduced plant growth. However, consistent published data on the mechanisms underlying this salt tolerance is lacking. To address this, we conducted a greenhouse experiment to assess the effects of moderate (75 mM NaCl) and severe (150 mM NaCl) salinity on whole-plant performance, including biomass production, photosynthetic capacity, and water relations. Compared to the control (0 mM NaCl), increasing NaCl concentrations progressively inhibited biomass accumulation in all plant parts, with shoot growth more affected than root growth. This reduction in biomass was associated with declines in all measured photosynthetic parameters, except for leaf temperature, which increased under salinity stress. Salinity did not affect osmotic potential at full turgor (Ψs100). However, severe salinity led to more negative values for water potential (Ψw) and osmotic potential at the turgor loss point (Ψs0) compared to the control. Osmotic adjustment (OA) remained unchanged in both NaCl treatments, suggesting that OA does not contribute to the salt-adaptation mechanism in Damask rose. In contrast, both salinity treatments decreased the apoplastic water content by 50%. Leaf volumetric elastic modulus (ε) increased from 3.1 MPa in the control to 3.8 MPa under severe salt stress, indicating enhanced cell wall rigidity. Overall, the observed physiological responses suggest that Damask rose is highly sensitive to salinity. The improved cell wall rigidity may play a role in its ability to survive under saline conditions.