Growing Media and Nutrient Solution Concentration Affect Vegetative Growth and Nutrition of Laelia anceps Lindl

Abstract

The domestication of wild orchids for commercial production is a new endeavor, which may represent a sustainable alternative to the collection/harvest from natural populations of threatened or endangered orchid species. In the present study, the growth and nutrition of vegetative plants of Laelia anceps Lindl. as affected by three components of the growing medium (peat, volcanic rock, and/or horticultural grade charcoal) and the nutrient solution concentration, measured as osmotic potential (ψS), were assessed using mixture experiments methodology. Leaf dry mass (DM) was the highest when plants were irrigated with nutrient solutions of –0.076 MPa. The lower leaf DM at lower or higher ψS was influenced by the medium because plants grown in 100% volcanic rock exhibited no effect, whereas plants grown in either 100% charcoal or 100% peat had a marked reduction. Regardless of the ψS of the nutrient solution, the highest leaf DM was observed in mixtures of two components containing charcoal and peat at high proportions. Dry mass of pseudobulbs and roots was highest in plants irrigated with solutions of –0.051 MPa, especially in mixtures with charcoal or 100% peat. Decreasing the ψS of the nutrient solution resulted in increased shoot nitrogen (N) and potassium (K) concentrations and decreased concentration of phosphorus (P), calcium (Ca), magnesium (Mg), boron (B), manganese (Mn), zinc (Zn), and copper (Cu). Increasing charcoal proportion in the growing media resulted in increased plant iron (Fe) and Cu concentration. However, increasing volcanic rock reduced plant P and K and increased Mn concentration. A higher proportion of peat was correlated with a decrease in plant Fe concentration. Leaf DM fit models on which macronutrient:micronutrient or micronutrient:micronutrient ratios were calculated, suggesting that nutrient imbalance may be responsible for a plant’s responses. The coefficients with the higher values included a micronutrient:micronutrient ratio, suggesting that an extremely fine balance in the uptake of a given micronutrient in relation to other micro- or macronutrient is of major importance for adequate growth of Laelia.