A simulation model for dry matter partitioning in cucumber.

A dynamic model is developed for the simulation of the daily dry matter distribution between the generative and vegetative plant parts and the distribution among individual fruits in greenhouse cucumber. The model is based on the hypothesis that dry matter partitioning is regulated by the sink strengths of the plant organs. The sink strength of an organ is denned here as its potential growth rate, i.e. the growth rate at non-limiting assimilate supply. The sink strength of each individual fruit is described as a function of its temperature sum after anthesis and the actual temperature, that of the vegetative plant parts as a function of actual temperature only. The formation rate of nonaborting fruits is essentially a function of the source/sink ratio. Model results agreed well with the measured fluctuating distribution of dry matter between fruits and vegetative parts. The measured effects of three intensities of fruit removal were also simulated satisfactorily. When simulating the partitioning among individual fruits the final fruit size was simulated quite well. However, the growth rate of young fruits was usually overestimated and that of old fruits underestimated, because of dominance among fruits. This phenomenon could be accounted for by incorporating priority functions into the model. Finally, a sensitivity analysis of the model was performed to investigate the effects of some climatic factors, manipulations of the number of fruits on a plant and model parameters on dry matter distribution. Strategies to manipulate the dry matter distribution are discussed.