Germinação assimbiótica e crescimento inicial de Cattleya nobilior Rchb.f (Orchidaceae)

Abstract

This work was developed in the Laboratório de Cultivo in vitro of Faculdade de Ciências Agrárias of Universidade Federal da Grande Dourados, located in Dourados – MS, during the period of September 2009 to May 2012. This study was conducted with the objective of evaluating: (1) asymbiotic seed germination and protocorm development of Cattleya nobilior Rchb.f. as a function of seed time storage (90 or 210 days), nutrient media (MS, ½ MS, K and VW), agar concentration (0; 2; 4; 6 and 8 g L-1) and pre-germinating seed treatment for 30, 60 and 120 minutes in gibberellin (0; 0.5; 1.0; 2.0; and 4.0 mg L-1); (2) the effect of coconut water (0; 5; 10; 20 and 25%) and growth regulators BAP (0.0; 0.5; 1.0; 2.0 and 4.0 mg L-1) and NAA (0.0; 0.5; 1.0 and 2.0 mg L-1) on in vitro culture of plants of C. nobilior. Seeds from natural pollination and plants obtained from asymbiotic germination in the laboratory were used as study material. It was observed a high germination on ½ MS, MS or VW media, regardless agar concentration and gibberellin. At 210 days of storage, the germination decreased to 50%. MS and ½ MS media enabled the development of whole plants after 90 days of in vitro culture. The addition of 25% coconut water resulted in higher values of fresh and dry mass and greatest length of shoots. On the other hand, in the absence of coconut water, at 90 days of culture, there was a greater production of roots, and at 180 days of culture, there was high shoot and root production and greater root length. No effect of growth regulators was observed on shoots and roots number, shoot length and fresh weight of the plants. On the other hand, the survival and the percentage of fresh weight of aerial part increased with the addition of 4.0 mg L-1 BAP, while the larger number of leaves was observed with the addition of NAA 0.5 mg L-1 and root length was higher in the presence of NAA 2.0 mg L-1.