High Salinity Stimulates the Adaptive Response to Potassium Deficiency Through the Antioxidant and the NADPH-Generating Systems in the Roots and Leaves of the Halophyte Cakile maritima

Salinity is one of the most constraining environmental factors that limits plant growth and productivity because it disturbs mineral nutrition by triggering interactions at the interface soil roots. It implies a notable competition between sodium (Na+) and potassium (K+), with this last mineral being a key nutrient for plants. Using the halophyte Cakile maritima as a model plant grown in hydroponic conditions, this study was aimed to analyze how the simultaneous stressful conditions of high salinity (400 mM NaCl) and K+ deficiency (0 mM) for 15 days affect plant growth, ion balance, and antioxidant and NADPH-generating systems. Among the parameters analyzed, the most remarkable changes were observed in leaves, with drastic increases in the Na+/K+, Na+/Ca2+ and Na+/Mg2+ ratios, an enhanced accumulation of anthocyanins, and the induction of 3 new copper/zinc superoxide dismutase (CuZnSOD) isozymes in plants simultaneously exposed to both stresses. Taken together, the data revealed that the combination of both, high salinity and K+ deficiency, caused oxidative stress and modulated the whole antioxidative response of C. maritima in leaves and roots. Besides the differential response underwent by both organs, considering the different parameters analyzed under these stressful conditions, the most notable traits were that the effect of both stresses seems to be not additive and that salinity appears to improve C. maritima response to K+, a behavior not manifested in glycophyte species. Taken together our data support that, under extreme conditions that lead to an excess of ROS production, the induction of several CuZn-SODs in C. maritima may be one of the most outstanding strategies for the adaptation of this plant species to survive.

Automated summary

The simultaneous stressful conditions of high salinity and K+ deficiency affect the growth, ion balance, and antioxidative response of Cakile maritima. Leaves showed the most significant changes, including increased Na+/K+ ratio, enhanced anthocyanin accumulation, and induction of CuZnSOD isozymes.