Effects of nitrogen availability on mineral nutrient balance and flavonoid accumulation in Cyclocarya paliurus

Cyclocarya paliurus has traditionally been used as medicine or nutraceutical foods. This study aims at investigating flavonoid accumulation in C. paliurus dependent on nitrogen availability and the following internal mineral nutrient balance under controlled condition. The 1-year-old seedlings of C. paliurus were grown in five different nitrogen levels. Along with the N gradient, C/N was significantly decreased, and the concentrations of phosphorus, potassium, calcium and magnesium were changed within plant. In the leaves, the main accumulation organ in C. paliurus, the highest flavonoid accumulation was achieved in intermediate N level (N3), which was closely related to flavanone-3-hydroxylase (FHT) activity as they had the similar variation patterns. Correlation analysis suggested that internal mineral nutrient balance can significantly affect flavonoid accumulation, especially for Mg within plant. These data revealed that nitrogen availability and the following altered internal mineral balance can significantly affect flavonoid accumulation. This study can provide the basis for developing new agricultural practices to maintain high yield while still keeping the nutritional value of crop or medicinal plants.