Fontes de silício na micropropagação de orquídea do grupo Cattleya

Abstract

The purpose of this study was to determine the silicon source that provides better growth of Cattleya loddigesii orchid plants. Seedlings from seeds germinated in vitro with approximately 1.0 cm in length were inoculated in tubes containing 15 mL of modified Knudson C culture medium, added with sodium silicate (0, 5, 10 and 20 mg L-1) and potassium silicate (0, 5, 10 and 20 mL L-1), in all possible combinations. The culture medium had its pH adjusted to 5.8 ± 0.1 and solidified with 5 g L-1 of agar before the sterilization process at 121ºC and 1 atm for 20 minutes. The cultures were maintained in a growth room with irradiance around 35 µmol m-2 s-1, temperature of 25±1ºC and photoperiod of 16 hours. The experimental design was completely randomized in a factorial scheme with 5 replications and 20 seedlings per treatment. Seedlings of C. loddigesii presented better growth (number of roots, length of the aerial part and of roots) in the modified Knudson C culture medium added with 5 mL L-1 of potassium silicate and 20 mg L-1 of sodium silicate. A larger number of shoots is observed with the addition of 5 mL L-1 potassium silicate in culture medium, in the absence of sodium silicate.