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This study aimed to evaluate the effect of B and Ca concentrations on morphological responses and size of calli in Eucalyptus urophylla. Calli were obtained from the mid portion of hypocotyls removed from in vitro germinated seedlings. The callus structures were cultivated for 21 and 31 days, being kept in a modified N7 medium with concentrations of B (0; 25; 50; 100 and 200 μM H3 BO3 ) and Ca (0; 3.75; 7.5; 11.25 and 15 mM CaCl2.2H2O). Size of calli, presence of roots, friability, viscosity, presence of globular structures on the surface and presence of pigments were analyzed. Overall, the shorter culture period (21 days) allowed better development of callus structures. The combination of 50 μM H3 BO3 with 7.5 mM CaCl2.2H2 O at 21 days, and 100 μM H3 BO3 with 1.13 mM CaCl2.2H2O at 31 days, provided best results. Rhizogenesis responded differently according to B and Ca concentrations. Simultaneous omission of B and Ca inhibited the rhizogenesis, causing disruption of the callus, favored formation of globular and friable structures, with presence of anthocyanin. High concentrations of calcium promoted root induction in calli.
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