Foliar sprays of growth regulators and rhizosphere effect in Cajanus cajan Millsp. II. Qualitative changes in the rhizospheree and certain metabolic changes in the plant

Abstract

Foliar sprays of growth regulators affected the per cent distribution of individual species of the dominant group of Aspergilli in the rhizosphere of Cajanus cajan Millsp. Generally, physiological groups occurred in the order of starch hydrolyzing > nitrifiers > denitrifiers. A shift in the balance in favour of denitrifiers and a parallel increase in the incidence ofAzotobacter in the rhizosphere of NAA- and IAA-treated plants was observed. Sprays of 2,4-D, NAA and IAA promoted starch-hydrolyzing group. On the other hand, with sprays of MH and gibberellin, their incidence was considerably reduced. It is suggested that transport and accumulation of carbohydrates in the roots might limit the incidence of this group of bacteria in MH- and gibberellintrated plants. 2,4-D and NAA sprays stimulated amino-acid requiring bacteria while MH treatment tended to preferentially stimulate group-V organisms. These results are discussed with reference to metabolic changes in the plant.