Improving Aerial and Root Quality Traits of Two Landscaping Shrubs Stem Cuttings by Applying a Commercial Brown Seaweed Extract

The availability of quality planting material is one of the most important requirements for increasing the productivity of any ornamental crop. Horticulturists make use of auxins and apply them exogenously to cuttings to generate adventitious roots and balanced shoots. Many studies have illustrated the influence of seaweed extracts on the growth of ornamental crops; their use in vegetative cutting propagation, to our knowledge, has been little investigated. Moreover, there is a lack of information on the influence of IBA and seaweed extract concentration on the carbohydrate content. This research aimed to compare the effects of the commercial seaweed extract, called Goteo (R), with that of the phytohormone IBA, on the aerial and root quality traits of stem cutting in two Mediterranean landscaping shrubs: Lantana camara (S1) and Abelia x grandiflora (S2). The treatments applied to semi-hardwood stem cuttings were as follows: C0: untreated control; IBA concentration: 1250 mg L-1; Goteo (R) concentrations at 1, 2, and 3 mL L-1. In L. camara, the greatest values of rooting percentage were obtained under IBA and Goteo (R) treatments when compared to the control; in A. x grandiflora, there were no effects among treatments. The presented study shows that Goteo (R) stimulated adventitious rooting and provided a better rooting quality and shoot development of stem cuttings in Lantana and Abelia. In S1, cuttings treated with Goteo (R), at the dose of 3 mL L-1, were greater in the number of roots, growth traits, root morphology and carbohydrate content, than those treated with IBA. In S2, 1 mL L-1 Goteo (R) concentration could be recommended to obtain high-quality rooted stem cuttings.