In vitro culture of Achillea millefolium L.: quality and intensity of light on growth and production of volatiles

The influence of different light spectra and intensities was evaluated in an in vitro culture of Achillea millefolium L. (yarrow). The treatments were: use of light emitting diode (LED) lamps in the blue, red, green and white wavelengths, and the intensities of 13; 27; 35; 47 and 69 A mu mol m(-2) s(-1), obtained with a cool fluorescent lamp. At 45 days of culture in hormone-free MS medium, the production of dry matter, survival, rooting, length of shoots and roots, numbers of roots, pigments, as well as volatile constituents, were evaluated. The quality and intensity of light significantly influenced the in vitro growth of yarrow. In the experiment with LEDs, the blue spectrum provided the highest dry matter accumulation, number of roots, percentage of rooting and survival. In different light intensities, 27 A mu mol m(-2) s(-1) showed the highest values for the variables analyzed. Thus, blue LED spectrum or cool fluorescent lamp with 27 A mu mol m(-2) s(-1) benefits the in vitro growth of yarrow. A variation in number, content and profile of volatile constituents under the influence of quality and light intensity was also observed. The major constituents identified were sabinene, 1,8 cineole, borneol, beta-caryophyllene and beta-cubebene, independent of the light treatments. The amount and composition of the volatile compounds ranged with the intensity and quality of light. Thus, it is possible to adjust the ambient light in order to yield the compounds of interest.