The effects of indole-3-butyric acid root dips on the root development and shoot growth of transplanted Fagus sylvatica L. and Quercus robur L. seedlings

Abstract

SummaryThe effects (and interaction) of different indole-3-butyric acid (IBA) concentrations and duration of dipping on the growth of transplanted, two year old seedlings of common oak (Quercus robur, L) and beech (Fagus sylvatica, L.) was investigated using a combination of separate experiments in plants pots and mini-rhizotrons. The roots of seedlings were dipped in all combinations of the following concentrations and durations: 0, 250, 500, 1000, 2000 mg l–1 IBA; 1, 10, 100 and 400 min. IBA 250–1000.mg l–1 increased root initiation, root elongation, shoot growth and leaf area of the beech seedlings and this resulted in increases in dry weights of these organs after 54 and 105 d. However, within this range of concentrations there were no differences in effects. IBA 2000 mg l–1 increased early root initiation more than any of the other treatments, but a high proportion of these new roots died and, ultimately, the mean total dry weight of these seedlings was less than that of the control. At IBA 250 mg l–1, increasing dipping time to 100 min or more increased the dry weight of roots and shoots, whereas at greater concentrations of IBA, dipping time had no influence. Treatment of oak seedlings with IBA at any concentration did not alter root initiation and elongation rates, and after 54 d, root length, shoot growth, leaf area and leaf numbers remained unaffected by IBA application. Bud break was delayed in seedlings treated with IBA at 500 mg l–1 or more, but after 110 d the dry weights of roots and shoots of the seedlings in all treatments were similar. Increasing the duration of dipping also had no effect on oak seedling growth. IBA uptake was found to be very low (<0.15% after 300 min) in cut roots of both species, but it was faster in beech than oak.