Iron concentrations in the in vitro cultivation of native Brazilian orchid Schomburgkia crispa

Resumo

In vitro cultivation is a highly important biotechnological method widely used for the production of orchid seedlings, but it is necessary to study the suitability of the nutrients used in different kinds of formulation, as the nutritional requirement varies according to the species. The objective was to evaluate different concentrations of iron in the in vitro cultivation of Schomburgkia crispa Lindl seedlings. Seedlings were obtained from seeds germinated in vitro. Modified MS culture medium was used with half of the macronutrient concentration. The micronutrients were added according to the original formulation, except for the iron which was added from a stock solution of FeEDTA (FeSO4.7H2O: 5.6 g L-1 and EDTA: 7.48 g L-1) at 0.0; 2.5; 5.0; 7.5; 10.0 and 12.5mL L-1. At 200 days after seedling transplantation, shoot height, root length, number of leaves, shoot number, leaf length, leaf width, aerial and root dry mass, chlorophyll a, b and carotenoids content were evaluated. A completely randomized design was used, with six treatments and ten replicates of five seedlings. Regression analysis was performed at 5% of significance. The increase in iron concentration caused a reduction in root length and an increase in the number of leaves and shoots. The concentration of 4.13 mL L-1 of FeEDTA was the one that provided the best in vitro growth of S. crispa plants. High concentrations of iron caused a reduction of initial development, but stimulated an increase in the number of shoots.