Rooting success using IBA auxin on endangered Leucadendron laxum (PROTEACEAE) in different rooting mediums

Abstract

Leucadendron laxum (Marsh rose Leucadendron) was tested for its rooting ability as an endangered plant species for reintroduction into the natural habitat, using IBA liquid hormone preparations and four growth media. The treatments included a control, 500, 1000, 2000 and 4000 ppm concentrations. Four growth media, namely: bark and polystyrene; peat moss and polystyrene; bark, river sand and polystyrene; and perlite and river sand were tested in an environmentally controlled greenhouse with bottom heat. The experiments used a randomised block design with 10 cuttings per treatment and 4 replicated four times. The results showed that the bark, sand and polystyrene medium had the highest (45%) significant survival rate when supplied with IBA at 500 ppm. The application of 1000 ppm of IBA in bark, sand and polystyrene medium significantly increased the number of roots per cutting (5) and produced the longest roots (4 cm). The bark and polystyrene medium supplied with zero IBA had the largest number of roots per cutting (6.5). The comparison of the four growth media showed that bark and polystyrene was the best medium that produced the highest and most significant callusing formation (30%), % of cuttings that rooted (28%), cuttings with a higher survival rate (57%), and cuttings with a higher number of roots (3.5) and the longest roots (7.35 mm). With regard to various IBA treatments tested across all treatments, the IBA supplied at 1000 ppm produced greater root numbers when compared with all other treatments.