Quantifying source–sink relationships in leaf-color modified rice genotypes during grain filling

Leaf-color modification can affect canopy photosynthesis, with potential effects on rice yield and yield components. Modulating source–sink relationships through crop management is often used to improve crop productivity. This study investigated whether and how modifying leaf color alters source–sink relationships and whether current crop cultivation practices remain applicable for leaf-color modified genotypes. Periodically collected data of total biomass and nitrogen (N) accumulation in rice genotypes of four genetic backgrounds and their leaf-color modified variants (greener or yellower) were analyzed, using a recently established modelling method to quantify the source–sink (im)balance during grain filling. Among all leaf-color variants, only one yellower-leaf variant showed a higher source capacity than its normal genotype. This was associated with greater post-flowering N-uptake that prolonged the functional leaf-N duration, and this greater post-flowering N-uptake was possible because of reduced pre-flowering N-uptake. A density experiment showed that current management practices (insufficient planting density accompanied by abundant N application) are unsuitable for the yellower-leaf genotype, ultimately limiting its yield potential. Leaf-color modification affects source–sink relationships by regulating the N trade-off between pre-and post-flowering uptake, as well as N translocation between source and sink organs. To best exploit leaf-color modification for improving crop productivity, adjustments of crop management practices are required.