IN VITRO DEVELOPMENT OF YELLOW LAPACHO (BIGNONIACEAE) USING HIGH-POWER LIGHT EMITTING DIODE

Handroanthus ochraceus (yellow lapacho) is a medicinal, ornamental and timber tree which can be propagated by in vitro culture. Conventional methods use fluorescent lighting (FL), whereas light emitting diode (LED) has been used for this purpose only recently. The aim of this work was to evaluate the effects of FL and high-power LED (HP-LED) on the in vitro multiplication and rooting of yellow lapacho at different irradiances (15 to 60 mu mol m(-2)s(-1)). Epicotyls obtained from half-siblings was multiplicated in WPM (Woody Plant Medium) supplemented with 20 mu M benzilaminopurine and 1 mM IBA (indolebutiric acid). For rooting, shoots were cultured for 3 days in 1/2WPM supplemented with 50 mu MIBA and for 42 days in auxin-free 1/2WPM under HP-LED or FL lighting. Under HP-LED, the multiplication rate of shoots increased significantly (61%) from 20 to 40 mu mol m(-2)s(-1) respect to FL. Differences in abaxial stomatal density and size were observed between light sources at 20 mu mol m(-2)s(-1). High HP-LED irradiance produced the highest rooting percentage. In the rooting stage, the marginal means of treatments without factors interaction showed that HP -LED irradiances significantly increased shoot length by 20%, shoot fresh weight by 77% and shoot dry weight by 30% in comparison to the values under FL. The maximum values calculated from the regression curves were around 50 mu mol m(-2) s(-1)for HP-LED for all parameters except root lenght whereas were around 20 mu mol m(-2) s(-1) for FL for all parameters except fresh and dry weigth of shoot. Here we show that HP-LED lighting improve in vitro culture of H. ochraceus, reduced 81% energy consumption respect to FL and uses only a multispectral LED instead of different single color LEDs. Therefore, HP-LED could be useful for the micropropagation of tree species contributing to sustainable agriculture and ecological restoration of degraded areas.