EFFECT OF N6-BENZYLADENINE AND PHOTOPERIOD ON THE FLOWERING OF in vitro PROTOCORMS OF Bletia urbana (ORCHIDACEAE)

Abstract

Flowering is the initial stage of the reproductive phase in plants, it begins when specific environmental conditions occur that induce the production of hormones. In orchids, various factors induce flowering in vitro, including the addition of cytokinins to the culture medium; however, its effect is not clear due to its use in combination with other hormones and under various photoperiod conditions. In order to know the effect of N-6-benzyladenine (BA) and photoperiod on in vitro flowering of Bletia urbana (an endangered species) protocorms (immature tissue) were cultured in Knudson C (KC) medium with different concentrations of BA (1, 5, 10, 15, 20 and 30 mu M) and incubated under five photoperiod regimes: short, neutral, long and short/neutral and short/long combinations; additionaly, in another experiment, the flowering of plants cultured in basal KC medium and incubated at natural environmental conditions was recorded. After 35 weeks of culture, the number of flowers, shoots and leaves was counted, and the growth of the plants in terms of height and root length was recorded. Bayesian models, generalized linear models and linear models were used for the different responses. Models showed greater probability of flowering with concentrations of 20 and 30 mu M of BA; however, under such conditions the plants showed lower production of shoots, leaves and lower growth. Plants grown under natural conditions generated viable flowers, fruits and seeds, coinciding with their natural phenology. The flowers developed by protocorms presented abnormalities in color and diameter, unlike those developed by mature plants. In B. urbana protocorms BA induces flowering in vitro, with abnormalities that might be due to the use of immature tissue, the high inducing effect of BA, and the use of a nutrient-poor culture medium.