Effect of mode of application of some growth regulators on the physiology of tomato plants: I effect of IAA on the endogenous hormonal contents

ABSTRACT

Application of 10 ppm IAA concentrations to the culture media or used as foliar spray of tomato plants caused stimulatory effects on growth, differentiation, development and fruiting of plants. 40 ppm concentration however, caused less activation than that exerted by 10 ppm concentration. This was accompanied with regular increases in the contents and levels of auxins, gibberellins and cytokinins leading to hormonal balance. The high concentration of IAA [80 ppm] however induced inhibiting effect on the previously mentioned phenomena which were accompanied with increases in the level and activity of endogenous inhibitors mainly unsaturated lactones and also with low levels of auxins, gibberellins and cytokinins leading to hormonal imbalance. Also the IAA oxidase activity was enhanced by the application of higher concentration of IAA. These results can easily interpret the previously mentioned results in the first paper of this series