Indole Acetic Acid Production by the Indigenous Isolates of Azotobacter and Fluorescent Pseudomonas in the Presence and Absence of Tryptophan

Authors : Farah AHMAD, Iqbal AHMAD, Mohd Saghir KHAN

Pages : 29-34

View : 17 | Download : 9

Publication Date : 2005-12-01

Article Type : Research Paper

Abstract :A total of 21 bacterial isolates insert ignore into journalissuearticles values(Azotobacter sp., 10 and fluorescent Pseudomonas sp., 11); were isolated from different rhizospheric soils in the vicinity of Aligarh city and characterized as per standard methods. These isolates were further tested for the production of indole acetic acid insert ignore into journalissuearticles values(IAA); in a medium with 0, 1, 2 and 5 mg/ml of tryptophan. A low amount insert ignore into journalissuearticles values(2.68-10.80 mg/ml); of IAA production was recorded by Azotobacter strains without tryptophan addition. Seven Azotobacter isolates showed high level insert ignore into journalissuearticles values(7.3 to 32.8 mg/ml); production of IAA at 5 mg/ml of tryptophan while at 1 and 2 mg/ml the production was in the range of 1.47 to 11.88 and 5.99 to 24.8 mg/ml, respectively. Production of IAA in fluorescent Pseudomonas isolates increased with an increase in tryptophan concentration from 1 to 5 mg/ml in the majority of isolates. In the presence of 5mg/ ml of tryptophan, 5 isolates of Pseudomonas produced high levels insert ignore into journalissuearticles values(41.0 to 53.2 mg/ml); of IAA while 6 other isolates produced IAA in the range of 23.4 to 36.2 mg/ml. Production of IAA was further confirmed by extraction of crude IAA from 3 isolates of Azotobacter insert ignore into journalissuearticles values(Azs1, Azs6 and Azs9 ); and three isolates of Pseudomonas insert ignore into journalissuearticles values(Ps1, Ps4 and Ps7); and subsequent TLC analysis. A specific spot from the extracted IAA preparation was found corresponding with the standard spot of IAA with same Rf value. Pseudomonas isolates insert ignore into journalissuearticles values(Ps1, Ps4 and Ps7); showed inhibitory effects on the growth of root elongation of Sesbania aculeata and Vigna radiata at all concentrations of tryptophan compared to the control. However, the isolates of Azotobacter insert ignore into journalissuearticles values(Azs1, Azs6 and Azs9); demonstrated stimulatory effects on both plants. Increasing the concentration of tryptophan from 1 mg/ml to 5 mg/ml resulted in decreased growth in both S. aculeata and V. radiata. On a comparative basis isolate Azs9 was most promising in promoting plant growth. On the other hand, high concentration of exogenous tryptophan could exhibit toxic effects on plant growth.
Keywords : Indole acetic acid, Tryptophan, Azotobacter, Pseudomonas