KNO3 e NH4NO3 no cultivo in vitro de orquídea (Cattleya loddigesii ‘Tipo’)

Abstract

The objective of this work was to find the best concentration of KNO3 and NH4NO3 in orchid cultivation in vitro. Plantlets of species Cattleya loddigesii ‘Tipo’, with approximately 1 cm long were inoculated in BDS medium. The treatments consisted of the interaction of concentrations 0, 25, 50 and 100% of NH4NO3 and KNO3 , supplemented by 20 g L-1 sucrose, 2 g L-1 of activated charcoal, solidified with 5.5 g L-1 agar and pH adjusted to 5.7±0.1 before autoclaving at a pressure of 1 atm and temperature of 121° C for 20 minutes. After inoculation, the flasks containing the explants (5 plantlets per flask) were kept in a growth room with temperature of 25±2° C, photoperiod of 16 hours and irradiance 42 W m-2 provided by fluorescent lamps of the type of light special day (brand OSRAM 20W). The experimental design was completely randomized in factorial scheme 4x4, with five replicates, each replicate consisted of 4 vials. After 120 days of the installation of the experiment, it was evaluated length of shoot, number of shoots and fresh weight of seedlings. Best results for shoot length, number of shoots and fresh weight of seedlings were respectively 4.8 cm, 1.5 shoots and 0.61 g. The cultivation in vitro of Cattleya loddigesii ‘Tipo’ is reached in BDS medium containing 53-100% of KNO3 and 0- 50% of NH4NO3.