Leaf-colour modification affects canopy photosynthesis, dry-matter accumulation and yield traits in rice

Abstract

Recent research has proposed to modify leaf-colour traits to improve canopy photosynthesis ( A c ) by allowing light penetration to lower layers of a dense canopy. Whether and how enhanced light penetration can really increase A c and whether leaf-colour modification influences other growth-related traits remain unclear. Canopy light and nitrogen profile parameters (i.e., the extinction coefficient for light, K L ; and for nitrogen, K N ; and their ratio, K N / K L ), A c , and agronomic yield traits were examined in nine rice genotypes comprising different genetic backgrounds and their leaf-colour variants. Compared with stay-green (G) variants, yellow-leaf (Y) variants caused larger effects on crop growth and development: altered growth duration (increased in one genetic background while decreased in the other), lower tiller number, and reduced leaf area. As with G traits, a delayed senescence at the post-flowering stage was observed in Y variants, which was associated with nitrogen dynamics in plants. Although Y variants expectedly allowed more light penetration into lower layers of the canopy (i.e., lower K L ), the leaf-nitrogen profile, and thus, the leaf photosynthetic capacity (i.e., A max ) profile, did not necessarily follow more closely the light profile. Improved A c and higher daily crop growth rate (CGR) were observed in the Y variant of one genetic background but not of the other, and the higher A c or CGR were associated with improved leaf photosynthetic nitrogen use efficiency and higher canopy K N values. The higher CGR during the grain-filling phase and resulting increased harvest index of this Y variant contributed to its greater grain productivity. Multiple regression analysis of the data of all nine genotypes indicated that the K N : K L ratio was the most important factor determining A c and CGR. Leaf-colour modification can improve A c , CGR and crop productivity only if other traits (especially N profile in the canopy) are adjusted synergistically. However, the observed diversity in phenotypic variations of multiple traits caused by leaf-colour modification implies the potential of exploiting breeding or crop management to improve rice biomass and yield. • Effects of leaf-colour modification on rice photosynthesis and yield were assessed. • Importance of relative nitrogen: light profile to canopy photosynthesis was shown. • Leaf-colour modification also altered phenological and morpho-physiological traits. • These traits can be co-exploited to maximise benefits from leaf-colour alteration.