Modifications of water status, growth rate and antioxidant system in two wheat cultivars as affected by salinity stress and salicylic acid

Salicylic acid (SA) has an important role in drought-tolerance in wheat (Triticum aestivum L.) but its relevance to the salinity-tolerance is not well understood. In the present study, possible roles of SA and salinity responses were examined using two wheat cultivars i.e., drought-tolerant Sakha-69 and drought-sensitive Gemaza-1, exposed to 150 mM NaCl. Parameters were determined for growth i.e. fresh or dry mass (FM, DM), osmotic concentration (OC) of organic/inorganic solute, leaf relative water content (LRWC), photosynthesis pigment content (PPC), and selective antioxidant system (AOS) enzyme/molecule that might be involved in the stress remediation. Sakha-69 exhibited salinity tolerance greater than Gemaza-1 and SA ameliorated their salinity stresses like drought stress, suggesting that a common tolerant mechanism might be involved in the stresses. Salinity decreased root growth by 44-52% more strongly than shoot (36-41%) in FM or those in DM (32-35%). SA ameliorated root growth (40-60%) more efficiently than shoot (6-24%) for DM/FM. These results suggested that salinity and SA might target sensitive roots and hence influencing shoot functions. In fact, salinity reduced PPC by 10-18%, LRWC by 16-28%, and more sensitively, OC of inorganic solutes (K⁺, Ca²⁺, Mg²⁺) in shoot (19-36%) and root (25-59%), except a conspicuous increase in Na⁺, and SA recovered all the reductions near to control levels. SA and salinity increased additively most parameters for OC of organic solutes (sugars and organic acids) and AOS (glutathione and related enzyme activities), like drought responses. However, SA decreased the Na⁺ and proline contents and catalase activity in a counteracting manner to salinity. It is concluded from this experiment that SA-mediated tolerance might involve two mechanisms, one specific for minerals in root and the other related to drought/dehydration tolerance governed in the whole module systems.