MODEL ANALYSIS OF SHOOT ELONGATION IN CHRYSANTHEMUM X MORIFOLIUM

A prediction model is presented describing the effect of light integral and temperature on side shoot elongation in Chrysanthemum X morifolium cultivar 'Garland'. Daily increment in side shoot length is calculated by multiplying maximum daily increment with a light index (f(I)) and a temperature index (f(T)). The f(T) is related to the day/night heat sum ratio (Q(dn)). The model simulated the effect of seasonal variations in light integral and of day/night temperature regimes with an r2 value of 0.97 in relation to the data used for parameter estimation. In validation trials, the model overestimated the shoot elongation of plants grown in daylight growth chambers, while it underestimated the elongation of plants grown in a greenhouse environment (r2 = 0.91). The model can also be used to simulate the effect of daylength on shoot elongation but further work is needed to develop and validate this feature.