Effects of water stress and inoculation with plant growth promoting rhizobacteria (PGPR) on antioxidant status and photosynthetic pigments in basil ( Ocimum basilicum L.)

Abstract

Effects of water stress and inoculation with plant growth promoting rhizobacteria (PGPR) on antioxidant activity and photosynthetic pigments were studied in basil plants. A field experiment was conducted at the University of Zabol in Iran during 2010 growing season. The experiment laid out as split plot based on randomized complete block design with three replications. Three levels of water stress W 1 = 80 (control), W 2 = 60 and W 3 = 40% of the field capacity (FC) as main plots and four levels of bacterial species consisting of S 1 = Pseudomonades sp., S 2 = Bacillus lentus, S 3 = Azospirillum brasilens, S 4 = combination of three bacterial species and S 5 = control (without use of bacterial) as sub plots. The results revealed that water stress caused a significant change in the antioxidant activity. The highest concentration CAT and GPX activity were in W 3 treatments. By increasing water stress from control to W 3, chlorophyll content in leaves was increased but Fv/Fm and APX activity decreased. Application of rhizobacteria under water stress improved the antioxidant and photosynthetic pigments in basil plants. S 1 = Pseudomonades sp. under water stress, significantly increased the CAT enzyme activity, but the highest GPX and APX activity and chlorophyll content in leaves under water stress were in S 4 = combination of three bacterial species.