Better light spectral quality and thermal amplitude inside the greenhouse stimulate growth and improve acclimatization of in vitro –grown Cattleya warneri T. Moore

Growth and photosynthetic capacity of Cattleya warneri T. Moore seedlings cultivated in vitro were evaluated in two environments: (1) growth room (GR) with constant light, humidity, and temperature; and (2) greenhouse (GH) with variable humidity, temperature, and light intensity and quality. In both environments, two different tissue culture vessel lids were used: transparent plastic lids (TCVplastic) and non-transparent metal lids (TCVmetal). After 11 months of in vitro cultivation, five seedlings from each tissue culture vessel were evaluated for growth and photosynthetic capacity, while the other five seedlings of each tissue culture vessel were transferred to a greenhouse for acclimatization. Increased biomass production in vitro was observed in GH and GR (GH>GR). However, the photosynthetic capacity was not altered by the GH environment, since the net photosynthetic rate at 300 μmol m−2 s−1 (NPR300) was low in the final of period in all treatments. Therefore, the increase in biomass production in C. warneri was mostly dependent on the exogenous carbon source through the addition of sucrose to the culture medium. The use of TCVplastic in vitro improved seedlings’ growth in both GR and GH, showing an advantage in relation to TCVmetal. GH environment with quality light spectrum and thermal amplitude, and use of TCVplastic, increased biomass production in vitro and improved the acclimatization process of C. warneri seedlings, which also reduced electricity costs since the use of artificial light and air conditioning is not required.