Abstract
Spectral quality is an important factor for in vitro development of explants in a bioreactor system. Based on the need to optimize micropropagation for E. grandis × E. urophylla clones, the aim of the study was to assess the spectral quality of in vitro multiplication in temporary immersion bioreactor (TIB). The tissue used to generate the explants (i.e., the nodal segment with 1 cm of length and two axillary bud without leaves) was previously in vitro established and multiplied, it derived from ministumps of E. grandis × E. urophylla clone grown in a semi-hydroponic system. The spectral quality of in vitro multiplication was assessed through five light sources (i.e., fluorescent lamp, red, green, blue, and yellow cellophane). Morphological and anatomical features of tissues grown in TIB were evaluated at 90 days. Based on the results, yellow and blue spectral qualities were the most suitable to be adopted for in vitro multiplication of E. grandis × E. urophylla, since they enabled lesser hyperhydricity, favors high number of shoots per explant and shoot length, as well as thicker mesophyll and spongy parenchyma; arise as an alternative for large-scale production of eucalypts clonal plants.