High-resolution imaging of O 2 dynamics and metal solubilization in the rhizosphere of the hyperaccumulator Leersia hexandra Swartz.

The mobilization of trace metals in the rhizosphere can be affected by the redox potential, which is closely related to the O ₂ dynamics. This study examined the distributions of O ₂ and trace metals in the rhizosphere of the subaquatic hyperaccumulator Leersia hexandra Swartz under chromium (Cr) stress using planar optodes and the diffusive gradients in thin films technique coupled with laser ablation inductively coupled plasma mass spectrometry. The O ₂ concentrations and oxidized areas in the rhizosphere significantly increased with increases in the light intensity, air humidity, and atmospheric CO ₂ concentrations (p < 0.05). The O ₂ concentration first increased with increasing ambient temperatures, then decreased when the temperature increased from 25 to 32 ℃. The O ₂ concentration in the rhizosphere was significantly decreased under Cr stress (p < 0.05), with a prolonged response time to the altered ambient temperature. Cr stress led to decreased mobilities of As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Sb, V, W, and Zn in the rhizosphere, which were negatively correlated with the concentrations of O ₂ . These results provide new insights into the role of changes in the O ₂ concentration induced by the roots of hyperaccumulator plants in controlling the mobility of trace metals in soils.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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