Crescimento in vitro e ex vitro de melocactus zahntneri sob influência da fonte de luz e esterilização do meio de cultura.

Abstract

Endemic species of the Brazilian Northeast, Melocactus zehntneri has important medicinal value and it is also exploited for ornamental use. The in vitro cultivation of plants presents numerous advantages over the commonly used techniques, despite the high maintenance cost. The present paper aims to evaluate the in vitro and ex vitro growth of M. zehntneri with the use of different sources of the culture medium’s light and sterilization. For the in vitro germination and initial growth of the seedlings, simplified culture medium was used, which was physically sterilized by autoclaving (EF), or chemically (EQ) by the addition of calcium hypochlorite (0.01%). Cultures were maintained under fluorescent light sources - FL and LED Light Emitting Diode for 200 days. Subsequently, the plants were acclimatized in a greenhouse, where they remained for 130 days. At the end of the in vitro phase the percentage of germination, occurrence of contamination, growth parameters and photosynthetic pigment contents were evaluated. These last two variables were also examined after the ex vitro step, in addition to the plant survival rate. The use of LEDs only anticipated the beginning of germination, not differing from FL as the percentage. In the in vitro phase, the LED + EF treatment presented higher growth. The groups treated with LED positively influenced pigment biosynthesis. The LED + EQ treatment produced lower levels of carotenoids than LED + EF. In the ex vitro environment, the survival rate of the plants was 100% and those from the treatments exposed to the LEDs presented better development. For the pigment content, LED treatment increased the carotenoid content. The results show that the quality of light positively interferes with the growth of M. zehntneri more clearly than the sterilization type of the culture medium. In this way, it is recommended to use the combination of LED + EQ factors, which allowed to obtain better quality plants, besides besides allowing the reduction of costs.