Role of rhizospheric microorganisms in mitigating the adverse effect of salinity stress in Plantago ovata growth, biochemical and photosynthetic traits

Abstract

ABSTRACT This pot experiment was carried out to investigate the efficiency of plant rhizospheric microorganisms (PRMs) to counteract salinity stress in Plantago ovata. The treatments included soil salinity (2.5 (as control), 5 and 10 dS m−1), arbuscular mycorrhizal fungi (Control, Glomus mosseae, Rhizophagus intraradices and Funneliformis mosseae) and phosphate solubilizing bacteria (Control and Pseudomonas fluorescens). The highest amount of growth and yield parameters, relative water content (RWC), potassium (K+) and phosphorus (P) concentration, photosynthetic traits (chlorophyll a and b, carotenoid, maximal efficiency of PSII (fv/fm), variable fluorescence to initial fluorescence (fv/f0) and stomatal conductance (gs)), antioxidant enzymes and the lowest sodium (Na+) concentration, malondialdehyde (MDA) and electrolyte leakage were observed in the plants treated with mixture of Rhizophagus intraradices and Pseudomonas fluorescens under all salinity levels. Although all previously mentioned traits significantly and severely decreased under salinity stress, mucilage percentage, electrolyte leakage and Na+ concentration were increased under salinity levels. In conclusion, the results suggested that inoculation of AMF (particularly Rhizophagus intraradices) in combination with Pseudomonas fluorescens by the accumulation of proline along with decreased electrolyte leakage, maintenance of relative water content in leaves and selective uptake of K+ ions could overcome detrimental effects of salinity stress in isabgol. Abbreviations AMF: arbuscular mycorrhizal fungi; APX: ascorbate peroxidase; CAT: catalase; Chl: chlorophyll; CAR: carotenoids; ECe: electrical conductivity of soil saturation extract; EL: Electrolyte leakage; Fv/Fm: maximal efficiency of PSII; gs: stomatal conductance; Fv/F0: variable fluorescence to initial fluorescence; K+: potassium; MDA: malondialdehyde; Na+: Sodium; PGPR: plant growth-promoting rhizobacteria; P: phosphorus; PRM: plant rhizospheric microorganisms; PSB: phosphate solubilizing bacteria; RWC: relative water content; SOD: superoxide dismutase