Mineral nutricional, shoot collection and indol-3-butyric acid (IBA) on adventitious rooting and histology of Eucalyptus urophylla S. T. Blake minicutings

Abstract

The objective of this study was to evaluate the adventitious rooting in Eucalyptus urophylla minicuttings in relation to the nutrient solution concentrations, shoot collection and IBA and analyze histologically the adventitious rooting in relation to the concentration of nutrient solution, IBA and evaluation time targeting identifying the origin of the vascular connection. Shoots were collected originated from ministumps managed with three nutrient solution concentrations of 25%, 75% and 100% fertigated with 100ml of basic solution. The basal region of the cuttings were dipped for 10 seconds in IBA hydroalcoholic solution at two different concentrations (0 - free of IBA; 1000 mg L-1) in seven successive sampling to evaluate the amount of root, the longest root length, rooting and total height of cuttings. For histological analysis samples were dehydrated in alcohol-ethyl solution embedded in resin hydroxyethyl methacrylate, mounted histological slides, analyzed and photomicrographed with light microscope on a micrometric scale. The experiment was conducted in two parts with the first completely randomized in a factorial arrangement (3x2), and the factors consisting of nutrient solution (S1 - 100% S2 - 75% S3 - 25%) and the absence and presence of IBA (0 and 1,000 mg L-1), with four replications, each with four minicuttings. A solution of 100% and the presence of IBA favored the induction of a greater amount of root, the longest root length and total height of the cuttings for the 1st collection. It was not found significant difference for the 2nd and 3rd collections. For rooting the 1st collects 75% solution showed better average and the 2nd collect the solution of 75% and 100%, regardless of IBA favored rooting. The second stage corresponded 4th to 7th collection was conducted in the design randomized block in factorial arrangement (3x2x4) with split plot, and the factors consisting of nutrient solution (S1 - 100% S2 - 75% S3 - 25%), IBA (absence and 1,000 mg L-1) and collection of shoots (4 collections) with five blocks containing seven minicuttings each. Histological analysis was conducted in the design randomized block in factorial arrangement (3x2x4) with split plot, and the factors consisting of nutrient solution (S1 - 25% S2 - 75% S3 - 100%), absence and presence of IBA (1000 absence and mg.L-1) and four evaluation times (0, 10, 20 and 30 days). There was interaction between the factors for the amount of root, the longest root length, rooting percentage and total height of cuttings. Overall, the nutrient solution 75% and 100%, the presence of IBA and the 4th and 7th collection showed the best results as the adventitious rooting. It was histologically verified the formation of meristematic centers by the vascular cambium, and the adventitious root showed a direct connection to the vascular cambium.