Preharvest Abiotic Stress Affects the Nutritional Value of Lettuce

Lettuce (Lactuca sativa L.) is one of the most consumed leafy green vegetables in the world, and is a good source of important bioactive compounds. However, environmental stress factors, such as salinity or drought, cause physiological and biochemical changes in plants and influence the yields and levels of both primary and secondary metabolites, which drastically changes the nutritional value and quality of the crop. In the present work, six typical Czech cultivars/landraces of various lettuce morphotypes (Altenbursky, Dubacek, Kamenac, Jupiter, Prazan, and Robin) were grown under driven conditions and then analyzed for the content of sugars, fatty acids, amino acids, phenolics, and vitamins. Obtained data were subjected to compositional tables statistical analysis, which provided not only information on general trends in the changes in their nutritional value but also how these changes affected each particular variety. Overall, drought caused the largest relative increase in phenolic compounds and some amino acids. Conversely, drought caused overall the largest relative decrease in vitamin C, but also in fatty acids. In addition, salt stress caused a larger decrease in many metabolites, especially the amino acid arginine, while fatty acids were only slightly increased, together with vitamin E. In addition, the interpretation of data from statistical analysis showed that varieties Prazan and Altenbursky had the least changes in their chemical composition when subjected to drought stress. Again, var. Altenbursky showed the least variability in comparison to other varieties when subjected to salt stress. These findings confirm the fact that landraces and old cultivars do not change their chemical profiles significantly, as is the case for improved cultivars, and they emphasize the need for their cultivation when raising the productivity of staple food crops