PACLOBUTRAZOL AFFECTS THE EXTENSION GROWTH AND THE LEVELS OF ENDOGENOUS IAA OF ALMOND SEEDLINGS

The effect of paclobutrazol on plant height and the concentration of f ree indole-3-acetic acid (IAA) in almond seedlings grown in 0.5 L pots with moist perlite and subjected to 15 degrees C and photoperiod of 1 6 hours was studied. In the first two experiments the paclobutrazol wa s applied as a drench at 0, 0.5, 1.5 and 5 mg/pot. Seven and sixteen d ays respectively after application a gradual decrease in the growth ra te and concentration of free IAA in the tops of the growing shoots of almond seedlings on which paclobutrazol was applied, was observed. Fur thermore, a gradual increase in the concentration of free IAA in the f our younger leaves at the time of application was also detected. In th e third experiment the effect of paclobutrazol (5 mg/pot) on plant hei ght and the concentration of free IAA measured over 10 day period was studied. From the 4th day following application differences in the hei ght of seedlings and in the concentration of free IAA in the growing t ops between the control and treated seedlings were observed.