The dose-response curves for IAA and 4-Cl-IAA-induced growth of Zea mays L. coleoptile segments were studied as a function of time. Moreover, some characteristic growth parameters for both auxins were compared. The dose-response curve of growth rate measured after IAA or 4-Cl-IAA application was bell-shaped in all experiments. The optimum concentration was 10⁻⁶ M for 4-Cl-IAA and was found not to depend on the time of the growth measurement. However, in the case of IAA the optimum shifted from 10⁻⁶ M at the time of maximal growth rate to 10⁻⁵ M or even 10⁻⁴ M, when growth measured 3–4 hours after auxin application was analysed. The relative activity of 4-Cl-IAA-induced growth rate (as compared to IAA) increased significantly with increasing time from addition of this auxin to the medium. For both auxins the time needed to reach the maximal growth rate was clearly related to their concentrations. These data provided further evidence that 4-Cl-IAA is much more active auxin than IAA and can also suggest that IAA is more rapidly metabolized in comparison to 4-Cl-IAA.
A trumpet creeper (Campsis radicans) is an attractive vine propagated vegetatively through cuttings. So far, there is very little available data on propagation of this beautiful species in tissue culture. There was a research conducted in order to estimate the possibility to obtain rooted Campsis radicans plants that had been cultivated in tissue culture. The plant material were shoots obtained by multiplication on Murashige and Skoog [1962] (MS) medium which were put in fresh media supplemented with auxins: IAA (indoleacetic acid), IBA (indolebutyric acid) or NAA (naphthaleneacetic acid). The shoots were rooted in vitro or transplanted into soil (peat + perlite 1 : 1 w/v). It was noted that Campsis radicans is a very difficult plant to root in tissue culture. No rooting was obtained in vitro. Use of a stimulating passage with a hormone free medium or the ones containing IAA or IBA in concentrations of 2.5–5 mg·dm-3 and rooting shoots directly in soil allowed to obtain 100% of well rooted plants.