Expression analysis by real-time PCR. Relative expression of genes in the flavonoid pathway in various parts of the tomato plant. 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. Relative expression is given as a fold change related to the sample shoot top, day 0. Three analytical replicates were performed, SE is given (n = 3). Ubiqutin and elongation factor 1 α have been used as endogenous controls.