Ameliorative Effects of CaCl₂on Growth, Ionic Relations, and Proline Content of Senna Under Salinity Stress

Abstract

ABSTRACT The effect of NaCl and CaCl2 on growth parameters, ionic relations, and proline level in senna (Cassia angustifolia) plant was investigated in a pot culture experiment using NaCl (80 mM and 160 mM), CaCl2 (5 mM and 10 mM), and the combined salt of NaCl + CaCl2 (80 mM + 10 mM and 160 mM + 10 mM). These treatments were given to the growing plant separately at pre-flowering (A1), flowering (A2) and post-flowering (A3) stages. Observations were recorded at 15-day intervals from the time of treatments till harvest. Compared to the controls, biomass of the root, shoot, and leaf decreased significantly with each NaCl treatment, whereas the reverse was observed with CaCl2 treatments. Combined treatments of NaCl + CaCl2 applied at different stages reduced the biomass, but this reduction was less than the one observed with NaCl treatments alone. However, proline accumulation in the leaves was 8 times higher than in the controls with treatment of 160 mM NaCl + 10 mM CaCl2, whereas it was 5 times higher with NaCl (160 mM) alone. The concentration of K+ and Ca2+ was inhibited with NaCl treatments, while Na+ and Cl− levels increased in the different plant parts. CaCl2 treatment enhanced the K+ and Ca2+ concentration, while the combined treatments mitigated the adverse effect caused by NaCl. Thus calcium could alleviate the NaCl-induced inhibition of plant growth via the maintenance of net K+ to Na+ selectivity and the enhancement of proline accumulation in the leaves.