Effects of node position, number of leaflets left, and light intensity during cutting propagation on rooting and subsequent growth of domestic roses

Studies were conducted to develop an efficient cutting propagation method for domestic cut roses (Rosa hybrida Hort.). Three experiments were conducted in controlled environment growth chambers to investigate the effect of node position where the cuttings were taken, and number of leaflets left on each cutting, and light intensity on rooting and growth of the sapling. Domestic cut rose cultivars used in the first experiment for the effect of node position were standard type ‘Pink Song’ and ‘Gouni’, and spray type ‘Little Sun’ and ‘May.’ In the second experiment for the effect of number of leaflets left, standard type ‘Pink Song’, ‘Orange Beauty’ and ‘Gummack’, and spray type ‘May’ were used. In the third experiment for the effect of light intensity, standard type ‘Red Sun’ and ‘Gouni’, and spray type ‘Little Sun’ and ‘May’ were used. Cuttings were taken from third node positions each with a five leaflet. Each cutting had either 1, 3, or 5 leaflets by removing the rest of leaflets among five leaflets. Three light intensities used were 90, 180, and 270 μmol·m⁻²·s⁻¹. Node position only affected rooting percent. However, number of roots, root length and weight, and length of new shoot were not significantly affected by the node position. In ‘Pink Song’, ‘Little Sun’, and ‘Gouni’, the greatest rooting percent was observed in the 1–2th (top), whereas in ‘May’ it was observed 4–5th (middle) and 7–8th (bottom). Number of leaflets left on each cutting affected number of roots, root length and root weight, but not the length of new shoot and rooting percent. In ‘Gummack’, treatment with three leaflets left resulted in the greatest number of roots, length of the longest root, root weight, length of new shoot, and percent rooting. Also, similar results were observed in ‘Pink Song’, ‘May’, and ‘Orange Beauty’, except in length of new shoot. Optimum light intensity for rooting was 270 μmol·m⁻²·s⁻¹ for ‘Red Sun’, ‘Little Sun’, and ‘May’. In these three cultivars, rooting percent of the cuttings increased with increasing light intensity. In ‘Gouni’, however, the optimum light intensity for rooting was 180 μmol·m⁻²·s⁻¹.