Predicting the effect of irradiance and temperature on the flower diameter of greenhouse grown Chrysanthemum

A model was developed describing the influence of irradiance and temperature in the greenhouse on the size of Chrysanthemum flowers. In the model, flower diameter increment was related to a development index ranging from zero (start of SD) to unity (anthesis). The growth of the visible flower was divided into two different phases. In the first phase a linear function described the growth and development of the early visible flower bud, while the second phase, representing the opening process of the flower was best described with a monomolecular growth function. The effect of the climate on the two growth phases was modelled using empirical climate functions. Data, collected from a light and a temperature experiment, showed that low light integrals and temperatures above 20 °C had a retarding effect on flower growth. When the model was fitted to the observed data from the light experiment the R2-values varied from 0.999 to 0.965. Even the simulated diameter values matched the observed values from the temperature experiment well (R2-values from 0.998 to 0.966). When validated on independently collected data from two trials, the model could simulate the variations in the data with R2-values of 0.993 and 0.997.