Synergistic effect of phytoharmones and gypsum on alleviation of salt stress in rice plants

In many geographical areas, salinity is an environmental factor accounting for reduced crop productivity and deteriorates the soil quality. To minimize the injurious effect of salinity present study was conducted to evaluate the response of rice to foliar application of phytohormones salicylic acid (SA @ 10-5 M) and L-tryptophan (L-TRP @10-5 M) singly or in combination and soil-applied gypsum (with and without gypsum) under saline-sodic soil for the consecutive two years (2014-2015). Results showed that combined treatment of phytohormones (salicylic acid + L-tryptophan @ 10-5 M in 1:1 ratio) with 50% gypsum requirement of soil significantly (P ≤ 0.05) influenced growth and yield attributes of rice plants and increased the grain yield by up to 26% and 32.80% during 2014 and 2015 respectively compared with control. Results also demonstrated that individual application of salicylic acid or L-tryptophan improved the behavior of rice plants under salinity stress in comparison to control, however, best results in terms of yield and growth attributes were achieved in response to combined treatment of SA+L-TRP. Higher ameliorative efficiency in the terms of improved ECe, SAR, pHs, BD and HC were obtained with gypsum @ 50% GR in comparison to without gypsum application. Results highlighted that salinity tolerance of rice plants was enhanced under the cumulative effect of phytohormones suggesting that salicylic acid and L-tryptophan interact synergistically and proved a good strategy to alleviate salt stress. Keywords: gypsum; hormones; salicylic acid; L-tryptophan; rice; salinity. Abbreviations used: L-TRP (L-tryptophan); SA (salicylic acid); pHs (pH of soil saturated past); SAR (sodium absorption ratio); ECe (electrical conductivity of soil extract); HC (hydraulic conductivity); BD (bulk density); GR (gypsum requirement)