Formação de brotações e de raízes em segmentos caulinares de Pilosocereus chrysostele juvenis in vitro em função de citocinina

Abstract

In the brazilian semiarid northeast region, several cacti species are of great importance to the regional ecosystem. Some have potential to be used as ornamental plants and as livestock forage during the dry season. Pilosocereus chrysostele is a columnar cacti which has little scientific literature information available. It also suffers frequent human action. Advances in the knowledge of this species propagation methods are important for its proliferation. Therefore, micropropagation is relevant to the seedling availability. The study aimed to evaluate the effect of cytokinin in P. chrysostele morphogenesis. The experiment was conducted at Embrapa Tropical Agroindustry, in Fortaleza, Brazil. P. chrysostele plants with heights between 4.0 cm and 4.5 cm obtained from in vitro seeding were used. The experimental design was completely randomized in 2 x 6 factorial, being A factor explant types (apical and basal) and B factor concentrations of cytokinin (0.0, 0.5 , 1.0, 2.0 , 4.0 and 8.0 mg L-1 of BAP) in a total of twelve treatments, having five replicates per explant in a bottle. JADS culture medium supplemented with 30 g L-1 sucrose and 1.8 g L-1 of solidifying agent were used. The experiment was conducted in a growth chamber at temperature of 27 ± 2° C, in a 12 hour photoperiod and a photosynthetic irradiance of 30 µmol m-² s-1. At the 90th culture day, the shoots number was evaluated, besides the characterization of the shoots vigor, the presence of roots and the explant height. Apical and basal P. chrysostele stalk cuttings can be used as a source of explants when cultured in up to 1 mg L-1 BAP supplemented medium. Concentrations above 1 mg L-1 BAP can result in hyperhydric of the shoots.