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

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