Modeling the influence of cyclical plant growth and nutrient storage on N, P, and K absorption by hydroponically grown cut flower roses

Previous research found that a model using growth of new rose flower stems as the driving force for nutrient absorption did not adequately predict nutrient absorption of a whole plant. The objective of the current project was to develop a nutrient absorption model to take into account the dynamic nature (change in growth, nutrient demand, storage, and reallocation) of perennial plant parts on nitrogen (N), phosphorous (P), and potassium (K) absorption by roses. In this model we separate the plant into four organs: shoots, base leaves, base stems, and roots. Each organ exerts a relative influence on plant demand for a specific nutrient based on its degree of depletion for that nutrient which influences root nutrient absorption activity. Overall plant demand for the nutrient is expressed using the summation of each organ's relative contribution to plant demand. Nutrient absorption at the root level is expressed using Michaelis-Menten kinetics. Allocation of absorbed and stored nutrients takes place based on relative organ nutrient demand. A sequential harvest experiment was conducted using one-year old Rosa hybrida 'Kardinal' plants growing in solution culture to calibrate the model and a simulation was developed to compare predicted nutrient uptake and allocation with measured values from the calibration data set. The simulation demonstrates the importance of accounting for storage and mobilization of phloem mobile nutrients in predicting nutrient uptake dynamics in roses.