Enhancement of flavonoids and other antioxidants of loose-leaf lettuce by controlled supply of nitrogen (N) and sulfur (S)

Leaf lettuces have beneficial effects on human health, due to vitamins and phytochemicals, such as ascorbic acid, carotenoids, polyphenols and glucosinolates, that may protect key biological constituents. Different cultivation methods including control of nutrient supply may affect these compounds. Particularly, nitrogen (amount and form) and sulfur related to ammonium, play an important role on biosynthesis and accumulation of phytochemicals. In loose-leaf lettuce flavonoids are the most important phytochemicals. Differences among cultivars and effect of plant nutrition on content of flavonoids will be investigated in this project. Both teams will consider the influence of the nitrogen (N) amount and form, as well as sulfur (S) nutrition on loose-leaf lettuce (L. sativa var. crispa L.), but under different growing conditions. Several cultivars of this lettuce group gained popularity on the German market the last years and reduced the growing area of head and iceberg lettuce. The market demands in Croatia have been changed as well during past years, particularly after openings of big world supermarket chains. Both partners with their research teams have experience in the control of vegetable cultivation, especially in plant nutrition. Moreover, the German group has long term experience in the analyses of phytochemicals in vegetables. Therefore, both teams want to focus on leafy lettuce and its phytochemicals with beneficial health effects and complement each other in their expertise. Several experiments are proposed to be carried out by the graduated students both in their own team as well as in the other team.