Stem elongation of ornamental bromeliad in tissue culture depends on the temperature even in the presence of gibberellic acid

摘要

Acanthostachys strobilacea Link, Klotzsch, & Otto is an ornamental bromeliad native to Brazilian Atlantic Forest that naturally exhibits a rosette growth pattern. According to the temperature conditions of the in vitro culture, this species can exhibit stem elongation, facilitating the isolation of the nodal segments to be applied in its micropropagation. The rosette morphology is reestablished when this species is maintained under low temperature, thus allowing the maintenance of a germplasm collection (slow growth storage). Gibberellins (GA) are usually applied to stimulate stem elongation in micro-propagated plants. Thus, our aim here was to verify the influence of temperature over the stem elongation of A. strobilacea when GA3 is applied to the medium, thus estimating the use of this phytoregulator in slow growth cultures at low temperatures. Physiological and anatomical studies were performed on plants obtained from nodal segments maintained at 10, 15, 20, and 25 degrees C. Regardless of the applied treatment, no segments developed at 10 degrees C. Stem elongation occurred at 25 and 30 degrees C, and was not seen for plants grown under 15 and 20 degrees C. The application of 50 mu M of GA3 restored stem elongation in plants at 20 but not at 15 degrees C. The influence of gibberellins on stem elongation of this tropical bromeliad depends on the cultivation temperature, in which low temperature preponderates over the stem elongation effects of GA3. In addition, the optimum temperature for the slow growth of this species depends on the starting temperature of the explant used in the micropropagation.