ABSTRACT Melanoxylon brauna is propagated by seeds, however, low yield, pest attack and short viability are problems in seedling production. In vitro cultivation is an alternative for large-scale seedling production, but studies with this species are scarce. The aim of the work was to analyze the in vitro morphogenesis of braúna. Explants after induction of growth regulators. Three experiments were performed: I. In vitro bud proliferation of juvenile explants at different BAP concentrations. Was analyzed the number and length of shoots (mm); bud explants-1 (%); calogenesis (%) and direct and indirect organogenesis budding-1 (%). II. In vitro rhizogenesis of shoots with different types and auxin concentrations. III. In vitro rhizogenesis of under temporary immersion of shoots at different IBA concentrations. It was analyzed in experiment I and II: calogenesis (%); rhizogenesis (%); number, length (mm) and root dry mass (mg) the shoots. The nodal segment with two axillary buds was the most responsive explant regardless of the use of BAP. The stem apex with the use of BAP (2.5-3.5 mg.L-1) was the most responsive in the proliferation of shoots. Tested concentrations of auxins IBA, NAA and 2,4-D were not sufficient for in vitro rhizogenesis. The average of the maximum technical efficiencies of the variables used to analyze rhizogenic process suggests the treatment of the shoots base by temporary immersion in the IBA at an approximate concentration of 2,500 mg.L-1 and planting on the vermiculite substrate.

ABSTRACT The development of tissue cultured-based protocols applied to braúna, an endangeres species, would be though highly desirable. However, contamination-free explants are determinant for the success of this technique, which might be vulnerable to the toxicity of disinfectants. Here, we aimed at establishing an efficient protocol for in vitro production of axenic seedlings of braúna and to evaluate the toxicity of disinfectant agents in the Lactuca sativa model species. Experiments I and II: Seeds were treated with sodium hypochlorite (NaOCl) and fungicide captan, with and without residue, by different immersion times, respectively. The following were analyzed: contamination; germination and normal and abnormal seedlings. Experiment III: Lettuce seeds placed in Petri dishes were exposed to 2.5 mL captan at 0.5; 1; 2; 4 and 8%; 0.01% glyphosate and distilled water. The germination, length of seedlings, cell cycle, nuclear and chromosomal alterations of the cells of the root meristem were assesed. The isolated use of NaOCl was not efficient in the disinfestation of braúna seeds. However, the immersion of the seeds in captan, for 10 minutes with its residue, led to higher germination and vigor indexes; however, resulted in the formation of abnormal seedlings. This compound exhibited toxicity in the lettuce model seeds because affected the germination and the whole development of the seedlings, showing clastogenic and aneugenic action in the meristematic cell cycle.