Biosynthesis of auxins by azotobacter
2001
Khalid, M. | Arshad, M. | Khalid, A. | Zahir, Z.A. (University of Agriculture, Faisalabad (Pakistan). Dept. of Soil Science)
Various Azotobacter cultures were isolated from the rhizosphere of maize. Ten fast growing cultures were selected (numbered as Z1, Z2, Z10), and evaluated for their potential to produce auxins (IAA-equivalents) in vitro both in the absence and presence of auxins precursor, L-tryptophan (L-TRP). Azotobacter cultures varied in their auxins producing ability and Z4 was the most efficient auxins (3.1 mug IAA-equivalents mL-1) producer in the absence of L-TRP. Supplementation of the medium with L-TRP at a rate of 10-3 and 104M stimulated auxins production by almost 2-fold over the unamended control. Various environmental factors strongly affected L-TRP-dependent auxins biosynthesis in soil, and optimal productions were found at 6.0 mg L- TRP g-1 soil, 6.0 mg glucose g-1 soil, pH 7.0, 40 degree centigrade temperature, shaking at a rate of 150 rpm, no nitrogen and 48 hours of incubation. Application of antibiotics (streptomycin or erythromycin) had inhibitory effects on auxins biosynthesis in soil.
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