Model analysis of leaf unfolding rate in Malus domestica borkh.

Three dynamic models for predicting the response of leaf unfolding to temperature changes were developed for Malus domestica Borkh. cv. Karin Schneider. One model used a linear relation between leaf unfolding rate and temperature, while the other two models, called the A-model and the L-model, were based on the monomolecular growth equation. From data of daily mean temperature, daily photoperiod and daily light integral the number of leaves on the main shoot was predicted. Data were collected from experiments conducted in greenhouse and in daylight chambers. Plants were grown in temperatures ranging from 9 to 27 degrees C in natural day light and natural photoperiod. The total number of leaves on the main shoot was measured three times a week during the experimental period. Comparing predicted and observed development gave R(2) values of 0.946 for the linear model, 0.975 for the A-model and 0.947 for the L-model. Data were collected from a separate experiment for validation of the final models. In the validation experiments, plants were exposed to altering temperatures ranging from 9 to 27 degrees C. The linear and the A-model had the same R(2) value (0.992) in the validation step, while the L-model had an R(2) value of 0.978.