ACTIVATED CHARCOAL FOR IN VITRO PROPAGATION OF BRAZILIAN ORCHIDS

Abstract

This research focused on the effects of activated charcoal on the in vitro growing media used in the propagation of Brazilian native orchids. Activated charcoal has been described improving the in vitro plant growing and survival after transplant. Seeds were germinated in vitro and after three months they were transferred to one of the following media: MS (Murashige and Skoog) media; half strength of MS media; MS media supplemented with 1 g.L of activated charcoal; half strength of MS media supplemented with 1 g.L of activated charcoal; MS media supplemented with 2 g.L of activated charcoal; half strength of MS media supplemented with 2 g.L of activated charcoal. After six months the following features were evaluated, plantlet height, number of branches per plant, number of roots per plant, length of the roots, fresh weight and O. trulliferum was also evaluated concerning with the pseudobulb diameter. Just after the in vitro plant features evaluation they were transferred to pots containing the tree fern fiber and sphagnum. Two months after transplant the survival rate was evaluated for each treatment. Activated charcoal improved the in vitro plant quality and increased the survival after transplant of the three species evaluated. To M. flavescens and L. flava best results were obtained with half strength of MS media supplemented with 2 g.L of activated charcoal and O. trulliferum with MS media supplemented with 1 g.L of activated charcoal. INTRODUCTION Orchids are one of the most valuable and appreciated plants in the world. Due to its commercial value and beauty, orchids are very cultivated. Several species are in risk of extinction due to its predatory collection and destruction of its habitat. To preserve orchids using tissue culture technique is an option to produce orchids in large scale (Silva, 1986). An adequate formulation of the nutrition media is essential to tissue culture, because media must supply the essential substances for in vitro growth development (Caldas et al., 1990). Addition of activated charcoal on tissue culture media can be beneficial or adverse to growth and development. Its presence depends on the media, the specie and the tissue used and/or the objectives of the research (Pan and Staden, 1998). Activated charcoal as supplement on the media has been reported through the years by several authors due to its beneficial effects, such as, absorption of phenolic complex (Pan and Staden, 1998); root stimulator (George and Havishankar, 1997; Caldas et al., 1990); rhizome growth (Kim and Lee, 1992); development improvement (Choi and Chung, 1989); and absorption of toxic substances present in the media (Fridborg and Eriksson, 1978). Waes (1987) used activated charcoal for in vitro development of 18 species of European native orchids with concentrations from 0,02 % to 0,03 % (g.L) to improve in vitro development. The MS media contains nitrogen in ammonium and nitrate forms. Vitrification is frequent observed affecting plantlets development. Reduction of nitrogen concentration on ammonium has been used to reduce vitrification (Caldas et al., 1990). Reduction of MS media to half strength for in vitro orchid has been showed positive to reduce Proc. V IS on New Flor. Crops Eds.: A.F.C. Tombolato and G.M. Dias-Tagliacozzo Acta Hort. 683, ISHS 2005