Nitrogen deficiency maintains the yield and improves the antioxidant activity of Coreopsis tinctoria Nutt.

Nitrogen (N) deficiency levels were investigated for their potential to maintain the yield and improve antioxidant activity of Coreopsis tinctoria. Inflorescences and leaves at 0, 10, 20, 30, 40 and 50 d after flowering were frozen at -80 °C and plant growth, antioxidant activity, bioactive substance, enzyme activity and gene expression were evaluated. N deficiency maintained the total number of flowers, promoted phenol and flavonoid accumulation and enhanced antioxidant activity. Moreover, N deficiency stimulated activities of phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H) and 4-coumarate: coenzyme A ligase (4CL) and induced CtPAL, CtC4H and Ct4CL gene expression. The data also suggest that N deficiency-induced phenolic and flavonoid accumulation occurs due to the activation of biosynthetic pathways in C. tinctoria. We characterize the unique features of C. tinctoria under N deficiency conditions and provide valuable information for the cultivation of high-N use efficiency varieties with low input and high output.