Adventitious Rooting and Browning are Differentially Controlled by Auxin in Rooting-Recalcitrant Elegia capensis (Burm. f.) Schelpe

摘要

Industrial propagation of horticultural species involves adventitious root (AR) induction, which is difficult to establish in rooting-recalcitrant species. One of these recalcitrant species is Elegia capensis (Burm. f.) Schelpe. This monocotyledonous species was used to investigate the correlation between tissue browning and AR formation. To evaluate the root-inducing potential of various auxin treatments, a test system using stem segments of in vitro grown Elegia shoots was developed. In addition to exogenous auxin treatments, the effect of more sucrose in the medium and the effect of different light quality were evaluated. The auxins IAA, IBA, NAA, and 2,4-D did not induce roots under standard light conditions, which confirmed the strong rooting-recalcitrance of E. capensis. However, in the dark, IBA successfully induced roots in 20-40 % of the segments, depending on the auxin concentration applied. Excised stem segments showed browning upon incubation with auxins. Browning was dependent on auxin type and concentration, yet it did not correlate with the capacity to form roots because AR formation was observed on brown stem segments. We therefore conclude that browning does not cause rooting-recalcitrance in E. capensis.