Propagation of Hedera helix: Influence of irradiance to stock plants, length of internode and topophysis of cutting

Abstract Stock plants of Hedera helix cv. Pittsburgh were grown in controlled environment rooms at four different irradiances (light intensities) 10, 22, 37 or 46 W m^-2 PAR (photosynthetically active radiation). The root formation on single internode cuttings from these stock plants was observed in relation to length of the internodes and the position on the vine (topophysis). The analysis indicated that the root number was primarily dependent on internode length which in turn was dependent on irradiance to stock plants and topophysis. The irradiance of 37 W m^-2 PAR was optimal for internode length and root number and the basal internode was the one which produced the greatest number of roots.