Less light, more growth? Effects of the abscence of light on roots of in vitro of Catasetum fimbriatum (Orchidaceae)

Regina A. Amadeu

Vol. 1, Issue 2, p14-16 (2019)


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ABSTRACT: Due to the beauty of their flowers, orchids are extremely valued and commercialized. However, under natural conditions, the chances of reproduction are low. Thus, in vitro cultivation becomes an excellent option for rapid proliferation and for obtaining numerous plants with high genetic and phytosanitary quality. Among the many factors utilized to increase the efficiency and speed of production of these plants is the addition of activated carbon, which has been used due to its positive influence on the height and rooting in some species. The objective of this work was to find a way to improve the in vitro development of Catasetum fimbriatum in a simpler and cheaper way, without the use of activated carbon. My hypothesis is that the effect of light deprivation on the roots of the orchid could result in a development equivalent to that of the plant whose culture medium has activated charcoal, since I believe the growth of the orchid is not helped by the charcoal itself, but by the darkness it provides to the plant. Specimens of Catasetum fimbriatum were used as study material. The plants were studied in three groups, the first one (control) in conventional culture medium, the second with addition of activated carbon and the third with light deprivation in orchid roots. After three months, the specimens were evaluated according to the largest length of the root, length of the largest leaf, shoot fresh mass and root fresh weight. I found significant variations (p <0.05) in the different groups, and the one with greatest relevance (statistical significance) was the length of the largest root between group 1 (activated charcoal) and 2 (deprivation of light), which showed longer roots. We can conclude that light deprivation would be a good alternative to activated charcoal, since a longer root length may favor the rooting of the plant when transferred to the growth vessel, although the root length of the plant may also depend on the presence of phenols. Other studies should be performed to clarify the nutritional influence of activated carbon on the in vitro culture of Catasetum fimbriatum.
KEYWORDS: Orchids; Catasetum fimbriatum; Activated charcoal; In vitro culture