The change of IAA concentrations accompanied with the role of Zn in removing B toxicity in different plant species different in their tolerance to B

Abstract

This study was conducted to study the change levels of IAA content accompanied with Zn in removing B toxicity in different plant species that are different in their tolerance to B toxicity namely : mung bean (sensitive) , cucumber (moderately tolerant) and tomato (tolerant). Results revealed that , the toxic level of B caused reduction of IAA levels and a significant increase in IAA - oxidase activity . When Zinc sulphate was added ,Zn caused an increase in IAA level and a decrease in IAA oxidase activity which was not significantly different form the control. The initial concentration of Zn in plants cuttings was related to their ability to the tolerance .The highest concentration was found in Tomato followed by Cucumber and Mung bean .The toxic level of B markedly reduced Zn concentration in the parts of plants cuttings .Treating these cuttings with Zn increased Zn concentration to levels that are not statistically different from that in the control cuttings .The toxic conc. of B increased B level in all parts of cuttings but B levels values were decreased down to its initial conc. when Zn was added .The tolerance mechanism of plant to toxic levels of B is increasing the uptake of Zn and decreasing the uptake of B.