We examined glucosinolates (GSLs) concentrations and profiles in shoot (leaf lamina, petiole, and stem or hypocotyl) and root (main, lateral, and fine roots) in different species of Brassicaceae (Brassica rapa, Br. nigra, Br. oleracea, Barvarea vulgaris, Sinapis alba, Nasturtium officiale) and in Tropaeolum majus (Tropaeolaceae). Ten plants of each species were grown in the greenhouse. The plants were harvested and separated into the different organs, freeze-dried, and analyzed for their glucosinolate content by HPLC.

Overall, the stem and the main root had the highest concentrations of total GSLs, whereas in most species, the lamina and fine roots had the lowest concentrations. GSLs concentrations of N. officiale (an wetland species) did not differ between shoot organs. Indole GSLs, which may be less effective defenses, were relatively higher in concentration in the fine roots.

These results suggest that overall plant species with GSLs show optimal defense allocation patterns within the plant: tissues that contribute the most to a plant’s fitness and have the highest probability of being attacked are the best defended.