Quality of light on the in vitro culture of Dendranthema grandiflorum cv. Rage: morphophysiological characteristics

In micropropagation, the maintenance of the growth rooms is labor-consuming and expensive, which increases the necessity of studies involving the manipulation and control of the culture conditions to optimize the in vitro growth. The quality of light may modify the morphogenesis of the plants through many processes mediated by receivers, which absorb the light in the blue and red region of the spectrum, being therefore, a viable way to increase the quality of the micropopagated plants. This work aimed at evaluating the effect of the spectral alteration under conditions of natural light on the morphophysiology of micropropagated chrysanthemum [Dendranthema grandiflorum (Ramat.) Kitam] plants. Nodal segments with one bud cultivated in vitro were used as explants. The medium used was MS with half of its salts concentration supplemented with 15g. L-1 sucrose. The incubation conditions were growth room (GR), this being the control treatment, greenhouse (GH) without shadow protection and greenhouse with 50% shadow in the colors black, blue, and red. The evaluation was done 60 days after the implantation of the assay. For the leaf number, GR showed to be the most effective incubation form, with a higher number of leafs. The same occurred with the number of roots and shoots and the average length of roots. For the aerial part length, GR and GH with shadow protection in all three colors were more efficient. Considering the anatomical aspects for stomatal density, a greater number of stomatal/mm(2) was observed in GH without shadow protection and in GH with red shadow protection. For the polar and equatorial diameters of the stomata, GR without shadow protection, followed by GR with shadow protection in the colors blue and red, presented a bigger stomatal diameter. With the presented results, it is possible to recommend the use of natural light for the in vitro cultivation of chrysanthemum, however, the manipulation of the spectral quality is not recommended.