Effect of Plant Growth Promoting Rhizobacteria on growth and physiology of dill (Anethum graveolens L) under Pb stress condition

Contamination of agricultural land is increasing. Lead is one of the most important heavy metals and one of the environment pollutants. Today the use of biological fertilizers, in agriculture obtaind more considered .biofertilizers has positive effects on soil and environmental as and can be suitable alternative for chemical fertilizers.Silicon has known as an element to reduce the toxicity of heavy metal. For evaluation of effect of plant growth promoting rhizobacteria inoculation and silicon nutrition on growth, physiological and biochemical indicators of dill (Anethum graveolens L) under lead stress condition, two seperated factorial experimens based on completely randomizad design was conducted in three replication in laboratory and research greenhouse of Mohaghegh Ardabili University at 2015-2016. Experimental factors included soil contamination by lead (0, 400, 600, 1000 mg/kg soil) The inoculation with plant growth promoting and silicon nutrition has done, the treatments of first experiment was soil inoculation by (Pseudomonas putida strains 10, strains 150 and 159 of Pseudomonas fluorescence and control). In secound experiment plants with concentration of 1mM silicon and water (as control) were sprayed, then physiological and biochemical growth indexes were measured. The result indicated that concentration of 1000 ppm of lead caused to a significantly reduction in case of all growth criteria, photosynthetic pigments, relation water content, membrane stability. This concentration of lead to increase the carbohydrates, leaf proline, antioxidant enzyme activity. The higher content of this element accumulation resulted in root and air part but the application of plant growth promoting rhizobacteria and silicon nutrition improve the toxcity of nickel in plant and accumulation of this metal decrease especially in air part of palnt. Keywords: Basil, heave metallead, plant growth promoting rhizobacteria, silicon