Mechanisms underlying the accumulation and detoxification of manganese in Celosia argentea Linn. leaves

As an essential trace element for plants, manganese (Mn) poses significant threats to ecosystems and human health when it accumulates excessively in soils and aquatic environments. Celosia argentea Linn. is a promising Mn hyperaccumulator. However, the regulatory mechanisms underlying leaf responses to Mn stress remain poorly understood, particularly regarding the interplay between stomatal dynamics and detoxification strategies. This study investigated the physiological and biochemical adaptive mechanisms of C. argentea leaves under Mn toxicity, with a focus on elucidating the roles of antioxidant defence systems, stomatal behaviour modulation, and Mn chemical transformation in detoxification processes. The experimental findings demonstrate three outcomes. (1) The antioxidant system mitigates Mn-induced oxidative damage through synergistic interactions between enzymatic and nonenzymatic components, although the defensive capacity becomes limited under extreme Mn concentrations. (2) The presence of Mn stress significantly reduces gas exchange parameters, specifically the transpiration rate (Tr) and stomatal conductance (Gs), in leaves, with more pronounced decreases observed in leaf tip parts, revealing the adaptive mechanisms in leaves under such stress conditions. (3) The chemical forms of Mn undergo dynamic transformations along concentration gradients, shifting from water-soluble fractions to protein-bound forms, which indicates the existence of an adaptive detoxification strategy. These findings provide theoretical insights and scientific evidence for understanding the heavy metal tolerance strategies of hyperaccumulators and advancing the application of phytoremediation technologies.