Seed Endophyte bacteria enhance drought stress tolerance in by regulating, physiological characteristics, antioxidants and minerals uptake.

Growth stimulating bacteria help remediate dry arid soil and plant stress. Here, sp. and sp. we used to study the stress ecology of and the environmental impact of water deficit on soil characteristics, growth, photosynthesis apparatus, mineral acquisition and antioxidiant defense. Plants inoculated with or had significantly higher (about 2 folds) soil carbon flux (soil respiration), chlorophyll levels (18%), net photosynthetic rate (33% in and 54% in ), (44%) stomatal conductance than uninoculated plants in stressed conditions. Both bacterial strains improved leaf growth (23-29%) and root development under well-watered conditions but reduced around (25%) root biomass under drought. Plants inoculated with or under drought also increased of about 27% leaf respiration and transpiration (48%) but decreased water use efficiency, photoinhibition (91%), and the risk of oxidative stress (ETR/A) (49%). Drought stress increased most of the studied antioxidant enzymatic activities in the plants inoculated with or , which reduce the membrane damage and protect plants form oxidative defenses. Drought stress increased K acquisition around 50% in both shoots inoculated with or relative to non-stressed plants. Plants inoculated with or increased shoot Na while root Na only increased in plants inoculated with in stressed conditions. Drought stress increased shoot Mg in plants inoculated with or but did not affect Ca relative to non-stressed plants. Drought stress increased about 70% K/Na ratio only in plants inoculated with relative to non-stressed plants. Our results indicate that inoculating barley with the studied bacterial strains increases plant biomass and can therefore play a role in the environmental remediation of drylands for food production.