Analysis of growth physiological changes and metabolome of highland barley seedlings under cadmium (II) stress

This study aims to investigate the physiological changes in growth and metabolic response mechanisms of highland barley under different concentrations of cadmium. To achieve this, cadmium stress was applied to green barley at levels of 20, 40, and 80 mg/L. The results revealed that, under Cd(II) stress, the chlorophyll content and photosynthesis in leaves of highland barley seedlings were inhibited to some extent. Additionally, the malondialdehyde (MDA) content and superoxide dismutase activity increased significantly, indicating that the seedlings were affected by oxidative stress. In addition, Cd(II) stress also significantly affected the accumulation of metabolites in highland barley seedlings, resulting in an increase in lipids and lipid molecules, organic heterocyclic compounds, and phenylpropanoids. Cd(II) stress also significantly interfered with phenylalanine metabolism, fructose and mannose metabolism, amino acid, sugar, and nucleotide sugar metabolism, and biosynthetic metabolic pathways of isoquinoline alkaloids. The increase in Cd(II) stress also resulted in elevated levels of soluble sugars, soluble proteins, and proline as defense mechanisms against the stress. Overall, barley has a very good ability to resist adversity, and the mechanism of barley's resistance to adversity has not been deeply investigated. Therefore, in this paper, we systematically investigated the stress resistance mechanism of barley to cadmium stress and found that the growth physiology and metabolism of barley seedlings were significantly affected by cadmium stress. Differential changes in metabolites and enrichment of metabolic pathways may be the main mechanisms for barley seedlings to cope with Cd(II) stress. This provides direction for selecting better varieties of barley.