Salicylic acid and chitosan mitigate high temperature stress of rice via growth improvement, physio-biochemical adjustments and enhanced antioxidant activity

Abstract

Sustainably increasing rice (Oryza sativa L.) becomes more challenging due to environmental stresses. High temperature stress resulting from global warming impact of climate change is highly damaging as it can cause growth and yield reduction of rice via cellular and physio-biochemical impairments. Application of either salicylic acid or chitosan can possibly increase plant's tolerance to different abiotic stresses; however, their combined mitigation effects remained inadequately explored. Thus, the objective of the current study was to evaluate the mitigation potential of combined salicylic acid and chitosan against high temperature stress of rice. The experiment was conducted in a factorial combination of two temperature regimes (optimum temperature [control] and high temperature); two salicylic acid levels (−SA: 0 mg L−1 and +SA: 140 mg L−1); and two chitosan levels (−Ch: 0 mg L−1, +Ch: 100 mg L−1) following a completely randomized design. High temperature impaired rice growth and productivity by negatively influencing all tested parameters; however, salicylic acid and chitosan could significantly mitigate those impairments. The mitigation on growth and yield contributing parameters was recorded at best 11 %, 21 %, 12 %, 75 %, 61 %, 46 %, 27 %, and 43 % for plant height, leaf area, shoot dry matter, pollen viability, effective tiller percentage, filled grain percentage, 1000-grain weight, and grain yield respectively. Highest alleviation in physio-biochemical parameters was also found at best 35 %, 68 %, and 67 % for leaf greenness, net photosynthetic rate, and stomatal conductance respectively with 28 % and 60 % respective increase in transpiration rate and proline concentration. Superoxide dismutase, catalase, ascorbate peroxidase and peroxidase activity were also boosted as high as 1.6-folds, 1.4-folds, 1.9-folds, and 2.6-folds respectively with subsequent reduction of 32 % lipid peroxidation and 34 % hydrogen peroxide concentration. For all tested parameters, the best positive effects were observed under combined salicylic acid and chitosan treatment. Individually, salicylic acid was found more effective than chitosan; however, their combined application resulted in significantly better alleviation responses over their individual application for most studied parameters. Our findings would contribute in present understanding of high temperature stress and would also help in strategizing better-suited management practices toward sustainable rice productivity.