Mitigation of adverse effect of cadmium toxicity in lettuce (Lactuca sativa L.) through foliar application of chitosan and spermidine

Abstract

Cd stress is considered among the most harmful abiotic stresses because of its toxicity and ability to alter the ultrastructure of plants. Lettuce has a strong ability to collect Cd from the soil but also has a negative effect on its development and nutritional quality. To address this issue, foliar sprays of chitosan and spermidine have been used as feasible remedies because of their reported ability to improve plant tolerance to heavy metals. The effects of Cd and foliar treatment with chitosan, spermidine and their combination on the morphological, physiological, and biochemical attributes of two Lactuca sativa L. varieties were estimated in this study. The experiment was performed in 48 pots with 2 varieties in a four-way completely randomized design (CRD) with 3 replicates. Cd stress was applied by using 0 and 10 ppm CdCl2. The concentrations of exogenous chitosan and spermidine were 200 and 145 ppm, respectively. Both Lactuca sativa varieties presented similar results under Cd stress and presented significant reductions in biomass. Foliar sprays of chitosan and spermidine increased the morphology, photosynthetic features, secondary metabolites, and antioxidant activity; decreased H2O2 and MDA; and improved RMP in both varieties. This work aims to provide useful insights into sustainable techniques for increasing lettuce plant resilience against Cd toxicity by explaining the synergistic effects of chitosan and spermidine.