Nutrient uptake potential of cut roses (Rosa hybrida L.) in soilless culture

Cut roses grown hydroponically in greenhouses produce flowers year-round in flushes, indicating changes in plant biomass during each flowering cycle. Due to this cyclical nature of productivity, it is difficult to optimize the supply of nutrients to plants in this system. To address these concerns, this research aimed to quantify the nutrient uptake of cut roses during a flowering cycle, identify the relationship between nutrient uptake and plant growth, and predict nutrient uptake potential using the nutrient uptake model developed based on Michaelis-Menten function. Data on nutrient uptake rate for NO₃-N, NH₄-N, P, K, Ca and Mg and on plant growth responses corresponding to nutrient concentration were collected weekly from selfrooted, one-year old Rosa hybrida 'Vital' plants grown aero-hydroponically in modified Hoagland solutions of six nutrient solution concentrations: 0.7, 0.8, 1.4, 1.6, 2.1, and 2.4 EC. For all macronutrients, nutrient absorption during a flowering cycle increased as solution concentration increased. Uptake rate for most macronutrients shifted in time, declining in the middle of flowering cycle when new shoots appear and then increasing as stems reach harvestable maturity. The model coefficients that were estimated based on nutrient uptake data fitted well with Michaelis-Menten function. This result indicated that nutrient uptake potential of cut roses grown hydroponically could be predicted by the new nutrient uptake model developed based on modified Michaelis-Menten function. The model predicted highest uptake potential (per unit root surface area and day) for NO ₃-N at 17.07 mmol m^-2 day^-1, followed by K (12.67 mmol m^-2 day^-1), NH₄-N (12.22 mmol m^-1 day^-1), Ca (4.39 mmol m² day^-1), P (3.12 mmol m^-2 day^-1), and Mg (1.57 mmol m^-2 day^-1).