Aclimatização de estrelícia: efetividade de substratos, fontes de nitrogênio e disponibilidade hídrica

Abstract

Strelitzia reginae is a tropical ornamental plant with great potential in the market for cut flowers and gardens. Its species faces difficulties in propagation due to its slow growth and seeds with dormancy. One of the alternatives to accelerate the propagation process is the use of micropropagation techniques. Among the stages of seedling production process, acclimatization is crucial for the gradual adaptation of the plantlets from the in vitro environment to the ex vitro. The objective was to determine the necessary elements to promote vegetative growth and efficient carbohydrate assimilation during the acclimatization of Strelitzia reginae derived from in vitro cultivation. The strelitzia seeds were immersed in sulfuric acid to break dormancy, followed by asepsis with sodium hypochlorite (NaClO) before being inoculated in MS medium. After 45 days, the seeds were transferred to a growth room with a photoperiod of 16 hours, a temperature of 25 ± 2 °C, and a photon irradiance of 36 μmol m-2 s-1. The experiments were conducted in four stages: In the first experiment, acclimatization was carried out using the following substrates: commercial (Rendmax® Floreira), expanded vermiculite, coconut fiber, and carbonized rice husk. In a second experiment, a solution of KNO3 was applied to the substrate at concentrations of 0.0, 2.5, 3.75, and 5.0 g L-1, and saltpeter at concentrations of 0.0, 7.0, 7.8, and 8.2 g L-1 per pot, separately. In the third experiment, acclimatization was performed using different nitrogen sources such as NPK (14-14-14), saltpeter, and KNO3 at concentrations of 3.2 g L-1, 3.75 g L-1, and 3.5 g L-1, respectively. In experiment 4, soil moisture was controlled at 100%, 66%, and 33% using two Arduino MEGA boards. Evaluations were conducted at the end of the acclimatization period, including measurements of shoot and root height (cm), number of leaves, total dry mass (g), and carbohydrate metabolism analysis. Based on the results obtained, it was possible to infer that coconut fiber is the best substrate for acclimatizing Strelitzia reginae, and at appropriate doses, saltpeter proved to be a good fertilizer for this plant species, while soils with 66% moisture promote greater growth and root development of this species.