Concentrações de silício e GA3 na propagação in vitro de orquídea em condição de luz natural

Abstract

This study aimed to evaluate concentrations of silicon (Si) and giberelic acid (GA3) in the characteristics of growth and multiplication of orchids under natural light. Seedlings of Cattleya loddigesii, grown from seeds produced by self-fertilization and germinated in vitro, were submitted to uniformization in modified KC culture medium during three months. Each bottle contained four plants of approximately 1.0 cm (explant) and 15mL of culture medium KC plus 2 g L-1 of activated charcoal. Treatments consisted of combinations of sodium silicate (0, 5, 10 and 15 mg L-1 ) and GA3 (0, 5, 10 and 15 mg L-1 ). The pH of the culture medium was adjusted to 5.8 ± 0.1 and made solid with 5 g L-1 of agar before the sterilization process. The cultures were maintained in a greenhouse. The experimental design was completely randomized, with 5 replicates and 20 explants each treatment. After 120 days, we evaluated the number of leaves, number of sprouts, number of roots, and average length of roots and shoots. The cultivation in vitro of Cattleya loddigesii under natural light depended on the concentrations of sodium silicate and GA3, with the best results obtained with 0-10 mg L-1 of GA3, associated with 0-5 mg L-1 of sodium silicate.