KINETICS OF THE PHYSIOLOGICAL AND ANTIOXIDANT RESPONSE TO WATER STRESS IN LETTUCE

Fresh foods with functional properties such as their antioxidant content are in increasing demand for their benefits to human health. The agronomic management of specific conditions as water stress could permit to obtain fresh foods with a high antioxidant content based on the plants response. In this project, the kinetics of the physiological and antioxidant responses to water stress were studied in lettuce (Lactuca sativa L.) to identify the appropriate conditions to obtain plants with a higher content of antioxidant phytochemical compounds. The response in terms of mineral composition was also studied. Before harvest, the plants were subjected to a water stress treatment and evaluations were performed on the days 0, 2, 4, 6, 8 and 10. The photosynthesis rate increased in response to water stress, reaching its highest values on day 4, while the highest content of phenolic compounds was determined on day 6. A physiological and non-destructive determination such as the photosynthesis rate could be used as an indicator of a high antioxidant content prior to harvest. The mineral composition and the plant morphology remained without important variations on day 6. The experimental evidence suggests that it would be possible to obtain lettuce plants as fresh food with antioxidant proprieties through the agronomic management of the water stress; however, further studies are needed in post-harvest and regarding human health benefits.