Predicting dry-matter partitioning between individual cauliflower leaves using a source limitation/sink hierarchy model

摘要

Data from a container and two field experiments were used to construct a model which describes dry-matter partitioning between individual leaves of cauliflower. Thereby a combined source limitation/sink hierarchy approach is applied, assuming earlysink-limited exponential growth followed by a source-limited growth phase. Increasing competition for assimilates from newly formed leaves with higher sink priority then decreases the availability of assimilates and determines the end of the growth phaseof an individual leaf. Leaf senescence is assumed to start when the growth rate of an individual leaf approaches zero. The end of senescence, i.e. the time of leaf death, is described using an empirical temperature sum function. The model was able to describe (r~2 = 0.97) and predict (r~2 = 0.90 and 0.87) the partitioning of dry matter between classes of leaves consisting of three and five individuals for the container and the field experiments, respectively. The parameter estimates obtained indicate that 2-3 leaves are growing simultaneously with high growth rates. The potential growth rate of sequentially newly formed individual leaves decreased during the growth period of cauliflower, probably due to assimilate competition from the initiated curd.The model presented may serve as a background for analysing and predicting translocation processes, which determine nitrogen harvest index and therefore nitrogen use efficiency.