Effects of naphthalene-1-acetic acid on the in vitro development of Cattleya bicolor Lindl. (Orchidaceae)

Abstract

The techniques of in vitro micropropagation allow the production of large amounts of plants. However, when transferred to the natural environment these plants are susceptible to rapid water loss. The induction of a larger number of roots in orchid plants propagated in vitro would provide a greater water uptake, thus reducing the effects of water loss and increasing the probability of plant survival. The present study aimed to analyze the effects of the synthetic auxin naphthalene-1-acetic acid (NAA) on the in vitro development of plants of Cattleya bicolor, especially regarding root formation. A quantitative analysis of biometric variables of plants grown in different concentrations of NAA (0.0; 0.25; 0.5; 1 and 2 mg.L-1) during 180 and 360 days were carried out. In 360 days, addition of 0.5 mg.L-1 NAA significantly promoted plant growth, increasing length and dry mass of shoot and root portion in relation to the control. Toxicity evidences were detected at 2 mg.L-1 NAA. Therefore, the use of 0.5 mg.L-1 NAA not only promoted the de novo formation and longitudinal growth of roots, but also stimulated shoot development of C. bicolor plants. The results presented in this paper represent an important scientific advance since the growth of most Orchidaceae species is very slow when compared to other herbaceous plant families.