Substrate Dependent Microbially Derived Plant Hormones for Improving Growth of Maize Seedlings

Abstract

Ten Azotobacter cultures were isolated from the maize rhizosphere and their auxin producing ability was measured colourimetrically. The auxin production by three efficient Azotobacter cultures (Z1, Z3, Z4) was also measured in the presence of filter sterilized L-tryptophan (at 10G 3 , 10G 4 and 10G 5 M). Azotobacter culture Z4 gave relatively higher auxin production and was selected for further experiments. Azotobacter inoculation in combination with 10G 4 M L-TRP gave maximum length and weight of maize roots, which was 117 and 60 percent higher than control, respectively. Leonard Jar experiments were conducted to study the response of shoot growth to Azotobacter inoculation and L-TRP application at 10G 4 M separately and in combination with each other. Results showed that maximum length and weight of shoots were recorded by applying Azotobacter in combination with 10G 4 M L-TRP which was 45.3 and 36.5 percent higher than control, respectively. The possible mechanisms of action are discussed.