Accumulation of flavonoids. Accumulation of flavonoids in vegetative parts of tomato plants was determined by HPLC using standards. Tomato plants were grown for 25 days on rock-wool with complete nutrient supply under continuous light. The rock-wool was rinsed with water to remove previous nutrient solution, and plants were randomly divided in two batches. Half the plants continued with complete nutrient solution, whereas the other half received nutrient solution with no nitrogen. Samples were taken before change of nutrients (day 0) and again after three days. One biological sample was pooled from 3 different plants. Three analytical replicates were run for each sample; standard error was less than 1%. Accumulation of a) rutin and b) kaempferol-3-rutinoside is given as μg/g fresh weight (FW).