INTERACTION OF PACLOBUTRAZOL AND INDOLE-3-BUTYRIC ACID IN RELATION TOROOTING OF MNNG BEAN (VIGNA-RADIATA) CUTTINGS

Paclobutrazol (PB) only slightly stimulated the rooting of mung bean c uttings but, interestingly, the number of adventitious roots formed wa s dramatically increased when PB was used together with indole-3-butyr ic acid (IBA). Application of PB in the first phase of root formation, when root initials are induced, caused the greatest enhancement of th e promotive effect of IBA on rooting. Investigation of the effect of P B on uptake, transport and metabolism of [5-H-3]-IBA in mung bean cutt ings revealed some changes in the rate of metabolism of IBA in compari son with control cuttings. PB was found to be involved in the partitio ning of carbohydrates along the cuttings. Application of sucrose, like PB to the base of IBA-treated cuttings enhanced the effect of IBA. Th e patterns of the effects of PB and IBA, separately and together, on r ooting were similar in defoliated and intact cuttings, however the num ber of roots was much lower in the defoliated cuttings, which lacked a source of assimilates. PB counteracted the effect of GA(3) in the upp er regions of the cuttings and seemed to increase the sink capacity at the base of the cuttings. The results of the present study clearly de monstrated the enhancing influence of PB on IBA stimulation of the roo ting of mung bean cuttings. It is suggested that PB may affect the rat e of metabolism of IBA during rooting and the status of the local sink , in the base of the cuttings, thus partially contributing to the enha ncement of the rooting-promotive effect of IBA.