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

Zhou, Zhenxiang; Struik, Paul C.; Gu, Junfei; Putten, Peter E.L. van der; Wang, Zhiqin; Yin, Xinyou; Yang, Jianchang


Context: Recent research has proposed to modify leaf-colour traits to improve canopy photosynthesis (Ac) by allowing light penetration to lower layers of a dense canopy. Research question: Whether and how enhanced light penetration can really increase Ac and whether leaf-colour modification influences other growth-related traits remain unclear. Methods: Canopy light and nitrogen profile parameters (i.e., the extinction coefficient for light, KL; and for nitrogen, KN; and their ratio, KN/KL), Ac, and agronomic yield traits were examined in nine rice genotypes comprising different genetic backgrounds and their leaf-colour variants. Results: 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 KL), the leaf-nitrogen profile, and thus, the leaf photosynthetic capacity (i.e., Amax) profile, did not necessarily follow more closely the light profile. Improved Ac 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 Ac or CGR were associated with improved leaf photosynthetic nitrogen use efficiency and higher canopy KN 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 KN:KL ratio was the most important factor determining Ac and CGR. Conclusions and implications: Leaf-colour modification can improve Ac, 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.