Influência da qualidade de luz e silício no crescimento in vitro de orquídeas nativas e híbridas

Abstract

The vegetative propagation techniques using tissue culture can be a valuable tool in the production of orchid seedlings. The objective of this study was to determine the concentration of calcium silicate and light quality that provides better growth in seedlings of native orchid (Brassavola perrine) and hybrid [(Laelia cattleya Climax "Tuilerie" x Laelia cattleya Sons Atout Rotunda) x Brassolaelia cattleya Startifire Moon Beach]. Seedlings from seeds germinated in vitro with approximately 0.5 cm long were inoculated in 250 mL flasks containing 60 mL of culture medium MS, plus calcium silicate (0, 0.5, 1.0 and 2.0 mg L-1) in environments of culture [natural (a greenhouse) and artificial (in a growth room)] in all possible combinations. The culture medium had its pH adjusted to 5.8 ± 0.1 and solidified with 5.5 g L-1 of agar before autoclaving at 121º C and 1 atm for 20 minutes. After 150 days biometrics and ultrastructural analysis (scanning microscopy) were carried out. Greater growth of seedlings was obtained with the use of 2.0 mg L-1 and 1.0 mg L-1 of calcium silicate for hybrid and native species, respectively. The orchid species in study are anfistomatic with the type tetracytic (hybrid) and anomocytic (native) stomata. The presence of silicon in the leaf structure provided correct development (absence of structural deformations) of seedlings of orchids.