Impact of Different Levels of Drought Stress on Cichoric Acid Production in Lactuca undulata

Lactuca undulata is an annual plant belonging to the Asteraceae family. Cichoric acid is one of the most important phytochemical compounds, which is used in the pharmaceutical and food industries. The main objective of the present study was to investigate the effects of drought stress on the morphological and physiological characteristics of Lactuca undulata. For this purpose, 45 days old seedlings were subjected to drought stress at water potential of 0, -0.3, -0.6, -0.9, and -1.2 bar. Polyethylene glycol 4000 was used to create and applydrought stress. The current results showed that by increasing drought stress, the plants gradually withered. The highest level of root and leaf dry and fresh weight, seedling total weight, root and leaf total phenol, leaf total flavonoid, root and leaf soluble sugar, root soluble protein, and root peroxidase enzyme activity were obtained under drought stress with water potential of -0.6 bar. However, the highest amount of root total flavonoid and leaf peroxidase enzyme activity were observed under drought stress with a potential -0.9 bar. The amount of root soluble protein gradually increased with increasing drought stress. But, root and leaf catalase activity showed a significant decrease by increasing drought stress, compared to control. Data from HPLC analysis showed that the highest amount of cichoric acid was obtained after drought stress with water potential of -0.6 and -0.9 bar. In conclusion, the present data showed that drought stress with a potential of -0.6 bar improves the growth factor and the amount of its secondary metabolites.