Controlled in vitro environment for stage II micropropagation of Buddleia alternifolia (Butterfly Bush)

Optimal light, sucrose, and CO₂ levels were determined for Stage II micropropagation of Buddleia alternifolia (Butterfly Bush). Five levels each of light (50, 75, 100, 125, 150 μmol m^-2 s^-1 PPF), of sucrose (0, 1, 2, 3, and 4%), and of force-ventilated CO₂ (0, 350, 600, 900, 1200 ppm) were compared through one-way factorial experiments. Three levels of each factor were then selected for a 3×3×4 factorial experiment of the same culture. Free-ventilated CO₂ of 350 ppm, serving as control, constituted the fourth level of CO₂. The results showed that the observed optimum points were 2% sucrose, 125 μmol m^-2 s^-1 PPF, and 600 ppm force-ventilated CO₂. Based on the lack of interactive effects between the factors, the general absence of statistical differences between the levels within each optimum factor range, and considerations of economic benefits, the preferred factor levels were chosen to be 3% sucrose, 350 ppm free-ventilated CO₂, and 75 μmol m^-2 s^-1 PPF. The study also revealed that elevated in vitro light and CO₂ levels, in the absence of sucrose, did not promote the growth of the culture.