Does the presence of leaves on coleus stem cuttings influence their rooting?

Abstract

Plectranthus scutellarioides (L.) R. Br. is part of the Lamiaceae family and is commonly known as coleus, due to the genus denomination in the past. This ornamental plant species has been gaining importance in the floristic industry due to the great number of exotic cultivars available in the market. Coleus commercial exploitation by seeds is held up by genetic instability, which makes it usually being propagated through semi-hardwood stem cuttings and leaves have great importance in stem cuttings adventitious rooting. The objective of this study was to evaluate the presence or absence of apical leaves and the use of indolebutyric acid (IBA) in coleus stem cuttings rooting. Semi-hardwood coleus stem cuttings with 6 cm long were prepared with or without apical leaves, and then treated with hydroalcoholic solutions (50% v v-1) of 0, 1000 and 2,000 mg L-1 IBA. The propagules were planted in tubes containing vermiculite and kept for 30 days in a greenhouse under intermittent misting (24 ± 2 °C, Relative Humidity 90%) until final evaluation. The experiment was conducted in a completely randomized design, in a 3x2 factorial scheme (3 IBA concentrations x presence and absence of apical leaves). The rooting was evaluated after 30 days. Stem cuttings with and without apical leaves has 100 and 57% rooting, respectively. Stem cuttings rooting did not vary according to IBA concentrations. Roots length and number were higher in stem cuttings with apical leaves in comparison to leafless ones, regardless IBA concentrations. On average, 97.7% sprouting was observed in cuttings with apical leaves, significantly higher rates when compared to the average of 2.2% on leafless cuttings. The presence of apical leaves is fundamental for coleus stem cuttings rooting and the use of IBA is not required for this species propagation.