Survey of bioactive metabolites in selected cultivars and varieties of Lactuca sativa L. under water stress

Plants respond to water stress with a variety of physiological and biochemical changes, but their response vary between species, varieties and cultivars. The present study focused on changes of bio-functional phytochemicals (phenolic compounds, chlorophyll, carotenoids, dietary fiber) in commercial cultivars and old, traditional varieties of lettuce under different water regimes (water-deficit, well-watered and water-logged). Results revealed lettuce varieties and cultivars with a different response behavior to water stress. Biomass production under drought conditions was reduced significantly in old varieties ('Struwelpeter', 'Trianon'), but in contrast, it was only affected tendentiously in the commercial cultivars ('Wiske', 'Teodore'). Carotenoid and chlorophyll contents decreased in both water extremes, while total phenols accumulated under limited water availability, predominantly found in 'Teodore'. Dietary fiber content was not influenced by different water regimes in all lettuce cultivars and varieties. Water stress reduced biomass production and led to a change of phytochemicals in lettuce, however, old and traditional varieties did not show a different water stress adaptation compared to commercial cultivars.