Stem cutting rooting, growth and anatomical responses of cacao tree clonal changes to the indole-3-butyric acid

The effects of indole-3-butyric acid (IBA) on growth and internal morphology of four clones of Theobroma cacao (CCN-10, CP-53, PS-1319 and CA-1.4) were evaluated. The IBA was applied in the base of stem cuttings, as an inert talc, in mixture concentrations of 2, 4, 6 and 8 g kg together with the control, without IBA. The evaluation of the growth of roots, stem and leaves of the four clones were accomplished by 160 days after the cutting (DAC) for all the IBA concentrations. However, the anatomical studies of the several plant organs were also made to the 160 DAC, but only for the concentration of 4g kg IBA and the control. The clone CA-1.4 presented increment in the root dry biomass (RDB) with the increase of the IBA concentrations, while for the other clones there were decreases of RDB starting from the 4 g kg IBA. The same fact was observed for the stem and leaf dry biomass, except for CCN-10 that did not answer to the increment of the concentrations of IBA. There was an increase of the total leaf area for the clones CP-53 e PS-1319 with the increment of the IBA (concentration up to 4 g kg), while the leaves number only increased for the clones CA-1.4 and CP-53, concentrations up to 8 and 4 g kg IBA, respectively. There was a decrease in the number of dead cuttings for the clones CA-1.4 and CCN-10 (up 8 g kg) of IBA and for the CP-53 (up to 4 g kg of IBA). The best IBA concentrations for the branch cutting rooting of the cacao clones CP-53, PS-1319 and CCN-10 were of 4, 4 and 6 g kg respectively, while for the clone CA1.4 was the one of 8 g kg; the increase of the IBA concentration promoted anatomical changes in the plant organs of all the clones, influencing the activity of the vascular cambium in the stem and inducing the formation of a larger number of adventitious roots in the stem cuttings.