Factors affecting auxin biosynthesis by wheat and rice rhizobacteria
2001
Khalid, A. | Arshad, M. | Zahir, Z.A. (University of Agriculture, Faisalabad (Pakistan). Dept. of Soil Science)
Microbially released auxins have great influence on plant growth and development. Thirty-one cultures of bacteria were isolated from the rhizosphere of different varieties of wheat grown at different sites and twenty-eight from the rhizosphere of rice. Relative efficacy of these isolates was determined for in-vitro auxins production. Among different rhizobacterial isolates, W9 showed significantly higher auxins production compared with all other tested isolates both in the presence and absence of its precursor, L- tryptophan. Various environmental factors such as substrate concentrations (L-TRP at a rate of 0 to 6 g L-1 growth medium), glucose concentrations (0 to 8 g L-1 growth medium), pH (6.5 to 8.5), temperature (25 to 45 degree centigrade), incubation period (24 to 96 hrs.) aeration (shaking vs. static) and antibiotics (erythromycin and streptomycin from 0 to 0.733 g L-1 growth medium) were tested for optimal auxins production in the liquid medium inoculated with the culture W9 isolated from wheat using colorimetry assay. The auxins biosynthesis was significantly influenced by the environmental factors and maximum productions were found to be at 5 g of L-TRP, 3 g of glucose, 7 pH, 30 degree centigrade temperature, 48 hours incubation and shaking at 100 rpm. Application of antibiotics had inhibitory effect on auxins biosynthesis.
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