Symbiotic association between Salix purpurea L. and Rhizophagus irregularis: modulation of plant responses under copper stress

There are increasing concerns about trace metal levels such as copper (Cu) in industrial sites and the broader environment. Different studies have highlighted the role of mycorrhizal associations in plant tolerance to trace metals, modulating some of the plant metabolic and physiological responses. In this study, we investigated the role of the symbiotic association between Rhizophagus irregularis and Salix purpurea L. in modulating plant responses under Cu stress. We measured Cu accumulation, oxidative stress-related, photosynthetic-related and hydraulic traits, for non-inoculated (non-arbuscular mycorrhizal fungi) and inoculated saplings exposed to different Cu concentrations. We found that S. purpurea is a suitable option for phytoremediation of Cu, acting as a phytostabilizer of this trace metal in its root system. We observed that the symbiotic association modulates a broad spectrum of metabolic and physiological responses in S. purpurea under Cu conditions, including (i) a reduction in gas exchange associated with chlorophyll content changes and (ii) the sequestration of Cu into the cell walls, modifying vessels anatomy and impacting leaf specific conductivity (K-L) and root hydraulic conductance (L-P). Upholding K-L and L-P under Cu stress might be related to a dynamic Aquaporin gene regulation of PIP1;2 along with an up-regulation of TIP2;2 in the roots of inoculated S. purpurea.