Effect of giberellic acid (GA3) and light on the in vitro germination of Cattleya warnerii T. Moore seeds

Abstract

The Orchidaceae is one of the biggest families of plants, widely distributed, including epiphytes, humics or lithophilous species. In general, the epiphytes have several adaptations to the environmental stress and lowermost seeds that, in natural way, germinate by the symbiosis with mycorrhizal fungi called symbiotic culture. Floriculturists has propagated several species in vitro using different culture means. The seeds of orchids germinate very slowly and some growth regulators like auxins and citocinins, besides photoperiods, have been used to speed up this process. The gibberelins are growth regulators that speed up the germination of some vegetal species propitiating an increase in the production of hydrolases which degrade the aleurone layer of seeds with endosperm. The aim of the present work was to verify the effect of the concentrations of 5, 10 and 20ml.l-1 of gibberellic acid (GA3), besides the influence of the continuous light, photoperiod of 16 hours and absence of luminosity on the Cattleya warnerii T.Moore seeds germinability, moreover to analyze the interaction of the luminosity with the culture mean. Four repetitions for each treatment had been made seeing that approximately 10,425 seeds were inoculated in each bottle. Two fluorescent light bulbs such as “day light” were utilized for the illumination and the temperature was of the ambient, which average during the experiments was approximately 26°C. The germination occurred in all the treatments, with significant difference enters the averages only for the dark regimen which presented the smallest values of porcentage of germination. The seeds of C.warnerii were indifferent to the light and the gibberellic acid hold up only the germination in the luminosity absence.