Impact of N, P, K, Mg and S deficiency on physiological and growth aspects of the orchid Dendrobium bigibbum

Dendrobium bigibbum is one of the main cultivated and commercialized orchids in the world. However, there is still lack of information on its nutritional requirements, plant response to macronutrient individual deficiency, and related biological harms. The objective of this study was to evaluate effects of N, P, K, Mg, and S deficiencies on physiological aspects, nutrient accumulation, dry matter production, and symptoms in D. bigibbum plants cultivated under nutrient solutions. Seven treatments were composed of a complete nutrient solution, solutions with individual omissions of N, P, K, Mg, and S, besides an only-water solution (control), organized in randomized blocks with 10 replications. Seedlings were planted in polyethylene pots of 1 dm³ volume, filled with vermiculite, and acclimatized along 30 days. After that, nutrient solution applications started according to the treatments along 90 days. D. bigibbum plants, for an optimum growth, present the nutritional requirements according to the following descending order: K ˃ N ˃ Mg ˃ P ˃ S. However, the species is sensitive to N, P, K, Mg, and S deficiency, what impairs the photosynthetic rate, stomatal conductance, and transpiration rate; it similarly harms plant dry matter production, causing visual symptoms which are characteristic of each nutrient deficiency.