The effect of nitrogen and phosphorus deficiency on flavonol accumulation in plant tissues

The flavonol content of Arabidopsis thaliana and tomato seedlings was assessed in conditions of reduced nitrogen or phosphorus availability. In both systems, a significant inverse relationship was observed between nutrient availability and flavonol accumulation, with nitrogen limitation promoting the greatest increase in flavonols. A trial was established to determine the effects of decreased nitrogen and phosphorus availability on the flavonol content of leaf and fruit tissues of tomato plants (Lycopersicon esculentum cv. Chaser) in a commercial situation. Nutrients were supplied by a hydroponic system with nutrient regimes designed to provide the highest and lowest nitrogen and phosphorus levels with which it is possible to support plant growth and fruit set. Fruiting was abundant and tomato fruits were harvested at mature green, breaker and red stages of ripening, leaves were also harvested from the tops of the plants. All tissues were analysed for flavonol content using reversed-phase high-performance liquid chromatography. Flavonol accumulation in the leaves of mature tomato plants was found to increase significantly in response to nitrogen stress, whereas phosphorus deficiency did not elicit this response. Reduced nitrogen availability had no consistent effect on the flavonol content of tomato fruits. Phosphorus deficiency elicited an increase in flavonol content in early stages of ripening. Effects of nutrient stress on the flavonol content of tomato fruits were lost as ripening progressed. The findings suggest that nutrient status may be employed to manipulate the flavonol content of vegetative tissues but cannot be used to elevate the flavonol content of tomato fruit.