Metabolomics and microbiome analysis elucidate the detoxification mechanisms of Hemarthria compressa, a low cadmium accumulating plant, in response to cadmium stress

Cadmium (Cd) is recognized as one of the most toxic heavy metal in the environment that causes pronounced phytotoxicity. This study investigated the physiological and biochemical responses and detoxification mechanisms of Hemarthria compressa under various concentrations of Cd stress (0, 30, 60, 90, and 270 mg·kg^-1). Our research findings indicate that the growth and photosynthetic capacity of H. compressa reach their peak at a Cd concentration of 60 mg·kg^-1. At this concentration, the Cd concentration in the shoots of H. compressa is 0.67 mg·kg^-1, the total Cd accumulation is 0.25 μg, and the MDA content is 6.25 nmol·g^-1, which represents the lowest values among all treatments.Metabolomics analysis reveals that sugar is related to Cd stress resistance, and the levels of organic acids involved in metabolic processes show only minor changes. H. compressa alters the composition of its root exudates by secreting substantial quantities of organic acids (such as citric acid, fumaric acid, and malic acid), sugars (such as trehalose, maltose, and glucose), and fatty acids (such as citraconic acid). These organic acids modulate the pH of the rhizosphere soil and recruit beneficial microorganisms, including Gp6, Sphingoaurantiacus, Devosia, and Neobacillus species, thereby enhancing plant growth and mitigating Cd accumulation.