Reza Khodadadi; REZA GHORBANINASRABADI
Abstract
Introduction Streptomyces is the most important and dominant genus of actinomycetales with more than 664 species which some of its species may stimulate plant growth through nutritional and physiological mechanisms that include: dissolution of phosphates, production of siderophores and phytohormones, ...
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Introduction Streptomyces is the most important and dominant genus of actinomycetales with more than 664 species which some of its species may stimulate plant growth through nutritional and physiological mechanisms that include: dissolution of phosphates, production of siderophores and phytohormones, biological Nitrogen fixation and production of antifungal metabolites. Silicon has significant positive effects on improving the growth and physiological characteristics of the plant by improving the root system, biosynthesis of phytohormones, resistance to biological and non-biological stresses and nutrient uptake. Improvement of the silicon concentration in the plant depends on its availability in soil. Soil application of resources with appropriate amount of silicon is of great importance in increasing the availability and uptake of silicon. It is also documented that the co-application of plant growth promoting bacteria and silicon is a useful and efficient method to increase plant growth and yield under normal and stress conditions. Due to beneficial effects of plant growth promoting bacteria and silicon in improving crop growth and also the importance of soil application of different silicon sources, the aim of this study was to Investigate the effect of Streptomyces isolate, silicon application using calcium-magnesium silicate source and the combined application of Streptomyces + silicon on growth parameters, chlorophyll content and accumulation of some nutrients in soybean (Glycine max L.)Materials and Methods A pot experiment was designed as factorial in a complete randomized design with 3 replications under natural light and temperature conditions. Experimental treatments included soil application of calcium-magnesium silicate source (37.9% silicon dioxide) at four levels 0 (M1), 200 (M2), 400 (M3) and 600 (M4) kg Si ha-1 and two levels of inoculation with Streptomyces isolates (no inoculation (B0) and inoculation with Streptomyces (B1). Surface-sterilized seeds were inoculated with a suspension of (107 CFU mL-1) Streptomyces isolate. The effect of experimental treatments on plant development stage (late vegetative growth period) was investigated. The soybean plants were harvested after 10 weeks of growth period from soil surface. Plant growth parameters including shoot and root biomass, root volume and plant height were determined. Also, chlorophyll content (a, b, Total) and concentration of nitrogen, silicon, phosphorus and potassium in the shoot were measured.Results and Discussion The results of the present study showed a positive and significant effect of the co- application of silicon and Streptomyces inoculation on improvement of the growth characteristics and chlorophyll content compared to their separate application. The highest amounts of shoot biomass (19.3 g per pot), root biomass (7.6 g per pot), root volume (38.07 cm3), plant height (98 cm) and chlorophyll a (18.07 mg / g), chlorophyll b (14.4 mg / g) and total chlorophyll (32.4 mg / g) were measured in the co-application of 600 kgha-1 Si (M4) and Streptomyces inoculation (M4B). .Our results showed the improvement of soybean growth parameters could be due to the positive effect of Streptomyces isolate on plant growth promotion and utilization of calcium-magnesium silicate in soil. Combined application of silicon and Streptomyces inoculation increased the concentration of silicon, nitrogen, phosphorus and potassium in the M4B treatment compared with the lonely application of highest level of silicon source (M4) by 16.25, 7.45, 45.6, 51.7%, respectively.Conclusion Based on the results of the present study soil application of calcium-magnesium silicate increased plant growth and physiological factors. Streptomyces inoculation improved the effects of calcium-magnesium silicate levels to enhance growth parameters, chlorophyll content and nutrient concentration (silicon, nitrogen, phosphorus and potassium) in soybeans. This study was carried out in pot experiment at the vegetative growth stage of soybean. Therefore, supplementary studies are necessary in field and harvest stage.Keywords: Streptomyces, inoculation, silicon, soybean, plant growth
