Physiological and metabolic responses of Lolium perenne L. roots to acid stress in cadmium-contaminated soil

Abstract

Perennial ryegrass (Lolium perenne L.) has potential in the phytoremediation of cadmium (Cd)-contaminated soil due to its strong Cd accumulation capacity and high biomass. In this study, we investigated the growth physiology, Cd accumulation, and metabolites of L. perenne roots under different soil acid stress levels (pH 4.0, 4.5, 5.0 and 6.0) and Cd concentrations (100 and 0 mg/kg) after 90 days of growth. The results showed that soil acid stress significantly impacts the remediation capability and physiological metabolic properties of L. perenne. Based on root Cd content and enrichment coefficient, soil pH between 4.5 and 5.0 was more conducive to Cd accumulation. The growth physiology and Cd accumulation of L. perenne were inhibited under high soil acid stress (pH 4.0). High soil acid stress caused a decrease in root length, root volume, and root biomass of L. perenne. Root malondialdehyde (MDA) content and the activity of antioxidant enzymes (catalase (CAT) and peroxidase (POD)) increased significantly in response to high soil acid stress to enhance tolerance. Metabolomics analysis revealed that acid stress resulted in significant changes in certain metabolites. Tartaric acid, fructose and amino acids (glutamate and lysine) in the roots of L. perenne were compatible solutes under acid stress. This study indicated that L. perenne has strong physiological and metabolic tolerance, as well as Cd accumulation ability, in response to soil acid stress.

Keywords

• adverse stress
• heavy metal
• metabolite profiling
• soil pollution