Low temperature, IBA concentrations and optimal time for adventitious rooting of eucalyptus benthamii mini-cuttings

Abstract

Eucalyptus benthamii is a forest species of economic interest that has difficulty with seed production and also is considered to have difficulty with adventitious rooting using propagation techniques, such as cutting or mini-cutting. We aimed to assess the adventitious rooting percentage under different storage times in low temperatures and at various IBA (indole-3-butyric acid) concentrations to determine the optimal time of permanence for rooting Eucalyptus benthamii minicuttings in a greenhouse. Shoots collected from mini-stumps cultivated in a semi-hydroponic system were used to obtain the mini-cuttings. For the first experiment, the mini-cuttings were stored at 4°C for 0 (immediate planting), 24, 48, 72, 96 and 120 h. The second experiment evaluated the rooting dynamic to determine the optimal time of permanence for minicuttings in a greenhouse. The basal region of the mini-cutting was treated with various IBA solutions: 0 (free of IBA), 1,000, 2,000, 3,000 and 4,000 mg·L−1. Every seven days (0 (immediate planting), 7, 14, 21 and 28 days), destructive sampling of the mini-cuttings was performed to evaluate the histology of the adventitious rooting. Eucalyptus benthamii minicuttings should be rooted immediately after the collection of the shoots. The 2,000 mg·L−1 IBA concentration induced a greater speed and percentage of adventitious rooting, and an interval of 35 to 42 days was indicated for permanence of the mini-cuttings in the greenhouse. Exposure to low temperature induced adventitious root formation with diffuse vascular connections.