Simulation and Prediction of Plant Phenology for Five Crops Based on Photoperiod×Temperature Interaction

This paper presents a plant phenological model based on genotypeitemperatureiphotoperiod interaction (GPTmodel). In the model, rate of development towards a specified stage (e.g. flowering) for a given genotype is composed of three components : the genotype's maximum rate of development ; any delay due to a non-optimal temperature ; and any delay due to a photoperiod response. It is assumed that development to the specified stage is an autonomous process established by most, if not all, genes other than the vernalization genes and the photoperiod genes ; and that this autonomous process is delayed by any activity of the photoperiod genes. Since all physiological processes are modulated by temperature, any photoperiod response is inevitably a photoperioditemperature interaction. This interaction is simulated by assuming that the photoperiod gene activity occurs only beyond a critical photoperiod (P c ) and is enlarged by temperature above a base temperature (T bp ) that allows the photoperiod gene activity. The model is written as R l 1 b kS t (TkT opt )#kS p (TkT bp ) QPkP c Q, where R is the expected rate of development to the specified stage under any combination of temperature (T ) and photoperiod (P). The other model parameters are : S p , the sensitivity to a delaying photoperiod ; T opt , the optimum temperature for development in the absence of the photoperiod response ; S t , the sensitivity to a non-optimum temperature ; and D b , the basic duration to the specified stage (or intrinsic earliness), the inverse of which is the maximum rate of development. D b is observable only if T l T opt and simultaneously P P c for long-day plants (LDP) but P P c for short-day plants (SDP). The model is shown to successfully simulate and predict the published phenological data of five crops, iz. long-day plants : pea (Pisum sati um L.), oat (A ena sati a L.), and wheat (Triticum aesti um L.), and short-day plants : bean (Phaseolus ulgaris L.) and maize (Zea mays L.).