Effects of Chloro-Organophosphate Ester on Photosynthesis, Chlorophyll Fluorescence, Antioxidation and Nutrients of Green Onion (Allium fistulosum L.)

Chloro-organophosphate ester (Cl-OPE) accumulation in soil and aquatic environments, and their potential hazard to crops, has attracted widespread attention. However, little is known about the potential adverse effects of Cl-OPEs on plants. Green onions are a specialty vegetable worldwide, and the heavy application of pesticides during their growth period has led to increasingly severe soil contamination in cultivation areas. We evaluated the toxic effects of Cl-OPEs on green onions and examined their toxicity mechanism. After 20 days of treatment, physiological parameters were measured across five biological replicates per treatment. Results indicated that as Cl-OPE concentrations increased, green onion leaf malondialdehyde (MDA) content and reactive oxygen species (ROS) levels rose significantly. Concurrently, the activities of the antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were significantly enhanced. However, leaf chlorophyll content and net photosynthetic rate (Pn) decreased significantly, indicating that Cl-OPE-induced oxidative stress inhibited photosynthesis. Meanwhile, the nutrient content of green onions gradually decreased as the concentration of Cl-OPEs increased. In conclusion, Cl-OPEs can damage chloroplasts by promoting ROS accumulation, which results in the yellowing of green onion leaves. The resulting decrease in Pn reduced the plant’s ability to assimilate nutrients.