Model of leaf biomass partitioning coefficient in different leaf ranks of rapeseed ( <i>Brassica napus</i> L.) main stem

Abstract Leaf growth is a dynamic process, and understanding the number of main-stem leaves and the distribution of leaf biomass at different development stages can provide a theoretical basis for the development of functional-structural rapeseed model. To address the gap in research on the leaf biomass partitioning coefficient model in the crop growth model, we developed the leaf biomass partitioning coefficient model for the main-stem at different leaf ranks in rapeseed. The outdoor experiment with cultivars, Ningyou 18 (V1, conventional), Ningyou 16 (V2, conventional), and Ningza 19 (V3, hybrid), and designed treatment of cultivars × fertilizer × transplanting density in the 2012-2015 growth season. The model was fitted by calculating the ratio of leaf biomass at different leaf ranks on the main-stem to the total leaf biomass on the main-stem, and normalizing the leaf ranks into (0-1] interval. We parameterized the model variables to elucidate how cultivar and environmental conditions influence the leaf biomass partitioning coefficients for different leaf ranks. The descriptive models were validated with independent experimental data, the correlation ( r ) of simulation and observation values all greater than 0.9 with significant levels at p &lt; 0.001. The absolute values of the average absolute difference ( d a ) are all less than 0.011 g g −1 . The ratio of d a to the average observation ( d ap ) for the normalized leaf rank, and leaf biomass partitioning coefficient at seedling stage, and budding and bolting stage, and blooming stage, and mature stage are 13.599%, 11.236%, 11.312%, 3.077%, and 8.661%, respectively. The RMSE values are all less than 0.032 g g −1 . The models developed in this paper have good performance and reliability for predicting leaf biomass partitioning coefficient of main-stem at different leaf ranks in rapeseed. This study integrates the leaf morphology model of rapeseed with the rapeseed growth model through biomass partitioning, contributing to the development of the functional-structural rapeseed model.