Abstract
Growth stimulating bacteria help remediate dry arid soil and plant stress. Here,
Pseudomonas
sp. and
Pantoea
sp. we used to study the stress ecology of
Hordeum vulgare
and the environmental impact of water deficit on soil characteristics, growth, photosynthesis apparatus, mineral acquisition and antioxidiant defense. Plants inoculated with
Pseudomonas
or
Pantoea
had significantly higher (about 2 folds) soil carbon flux (soil respiration), chlorophyll levels (18%), net photosynthetic rate (33% in
Pantoea
and 54% in
Pseudomonas
), (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
Pseudomonas
or
Pantoea
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
Pseudomonas
or
Pantoea
, which reduce the membrane damage and protect plants form oxidative defenses. Drought stress increased K
+
acquisition around 50% in both shoots inoculated with
Pseudomonas
or
Pantoea
relative to non-stressed plants. Plants inoculated with
Pseudomonas
or
Pantoea
increased shoot Na
+
while root Na
+
only increased in plants inoculated with
Pseudomonas
in stressed conditions. Drought stress increased shoot Mg
2+
in plants inoculated with
Pseudomonas
or
Pantoea
but did not affect Ca
2+
relative to non-stressed plants. Drought stress increased about 70% K
+
/Na
+
ratio only in plants inoculated with
Pseudomonas
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.