Modelling flower development in greenhouse chrysanthemum cultivars in relation to temperature and response group

Abstract

A general model was developed to describe the relationship between flower development, temperature and cultivar response group in greenhouse chrysanthemum ( Chrysanthemum morifolium). The rate of flower development was expressed as a function of a maximum rate, R max, which was multiplied by a temperature function and a light function. Furthermore, R max was expressed as a function of the cultivar response group. Data from previously published studies, concerning the temperature response of 30 cultivars, were used to estimate model parameters. The response groups of the cultivars ranged from 7.5 to 14 weeks. Parameters for `cultivar-specific' models and the general models were estimated. The temperature functions of the `cultivar-specific' models gave a good fit to data with R 2-values ranging from 1.000 to 0.966. Newer cultivars showed better tolerance to lower temperatures than older cultivars. The temperature curve of the general model was more in agreement with the newer cultivars than with the older. When validated on previously published data from the cultivar `Pert', the general model underestimated the rate of development at temperatures below 18°C, and overestimated development at 21 and 24°C. The use of `cultivar-specific' models and the general model is discussed together with the need to promote the introduction of `cultivar-specific' models in commercial production.