Auxin metabolism modulates rooting process in different geranium cultivars

Abstract

Abstract Geraniums are widely used ornamental plant species, mostly used as balcony plants. As a typical herbaceous plant species, it is generally believed that rooting is not a serious problem with this species. However, in practise, rooting has been shown to be highly dependent on the cultivar. In the present experiment, the rooting success of two cultivars, namely the easier-to-root cultivar 'Tango' and the more difficult-to-root cultivar 'Fire Cascade', was investigated based on the metabolism of IAA and its metabolite IAA aspartate. Cuttings of cultivar 'Fire Cascade', which had 2 to 5 times higher IAA concentration in their tissues immediately after abscission, rooted more slowly and formed a heavily stressed callus compared to cuttings of cultivar 'Tango'. Different hormone treatments applied to the cuttings prior to substrate insertion tended to decrease callus formation on the cuttings and tended to increase rooting in both cultivars. There were no statistically significant differences in IAA and IAA-aspartate concentrations in relation to the different hormone applications in cuttings, except in 'Tango' cuttings, where there was a significant relationship between hormone treatment and timing of IAA-aspartate concentration analysis.