Rhizogenesis of green cuttings of Catalpa bignonioides Walt. depending on the application of auxins

Abstract

Aims. In view of the increasing demand for high-quality planting material for urban landscaping, it is relevant to improve vegetative propagation technologies for promising ornamental species, particularly Catalpa bignonioides. Despite its high ornamental value, this species is used only to a limited extent in the southern Left- Bank Forest-Steppe of Ukraine due to the lack of seedlings. Methods. The study focused on evaluating the effectiveness of different types of auxins (indole-3-acetic acid — IAA, indole-3-butyric acid — IBA, naphthaleneacetic acid — NAA) and their concentrations in stimulating rhizogenesis of green cuttings of C. bignonioides. The experiment was conducted with freshly harvested green cuttings collected during the active growth period from the apical, medial, and basal parts of shoots. Results. The experiment showed that the highest rooting efficiency was observed in basal cuttings treated with IAA (50 mg/L), where rooting reached 85.5%, and the total root length exceeded 106 cm. Apical cuttings demonstrated the lowest rooting capacity, even when treated with auxins. Significant differences in the shoot growth of green cuttings of C. bignonioides were found depending on the type of auxins used (IAA or IBA) and the morphogenetic origin of the cuttings — in particular, basal and medial. The highest shoot growth was recorded in the variant with IAA treatment: the average shoot growth reached 19.5 cm, which was more than twice the value of the control. Conclusions. The study substantiates the feasibility of using basal and medial cuttings pretreated with IAA or IBA at a concentration of 50 mg/L for 24 hours. The results can be applied in developing vegetative propagation technologies for C. bignonioides under controlled conditions, followed by their implementation in ornamental and forest nursery practices.