Basal heat improves adventitious root quality in Plumeria (Plumeria rubra L.) stem cuttings of different sizes

Root development of hardwood cuttings of Plumeria rubra was investigated in relation to basal heat and the size of cuttings. Terminal cuttings of a clone grown in Sicily were trimmed to various lengths, ranging from 10 to 26 cm. To verify the cutting rooting response to basal heat, half of the cuttings were placed on a basal heated bench (28 ± 3°C, constant temperature) while the remaining were placed on an unheated bench (16-18°C during the night and 20-22°C during the day). Percent rooting and cutting survival were not affected by basal heat and cutting length. However, basal heat positively affected number of roots, length of longest root and bud growth. Increases in the length of the cutting resulted in a parallel increase in adventitious root formation. Medium (16-20 cm) and long (22-26 cm) length cuttings exposed to basal heat exhibited the best development in terms of number of roots, root length and bud growth.