Survival and development in vitro of Cattleya (Orchidaceae) submitted to treatments with different treatments of colchicines

Polyploidy produces desirable characteristicsin orchids that are represented by increase of the floral pieces, succulency degree, intensification of color, durability and larger resistance of flowers. The colchicine as polyploidy inductor agent in in vitro culture of plants has limitations, because when in high concentrations or very long treatments, it becomes poisonous for the vegetal tissues. The objective of this research work was to evaluate the influence of concentrations and times of exposition to the colchicine, on the survival and on the in vitro development of Cattleya tigrina. Protocorms were treated with colchicine in the concentrations of 0.5 and 1g. L-1 during 24, 48 and 72 hours. There were evaluated the tax of survival of the protocorms (%), percentage of plantlings with multiple buds and plant height after three and seven months. The increase of the concentration and of the time of exposition to colchicine caused a larger plant mortality and an increase of plantlings with reduced height.