Influence of magnesium on copper phytotoxicity to and accumulation and translocation in grapevines

• A free ion activity model is capable of modeling Cu toxicity to grapevine.
• Copper rhizotoxicity in grapevine is alleviated by milli-molar level of Mg.
• The accumulation and translocation of Cu in grapevine are affected by Mg treatments.

The phytotoxic effects of excess copper (Cu) on grapevines (Vitis vinifera L. var. Kyoho) were examined, both from macroscopic and microscopic perspectives, by using a fifteen-day hydroponic experiments. The influence of magnesium (Mg) on Cu phytotoxicity to, and accumulation and translocation in grapevines was also observed. For phytotoxicity effect, results showed that a relative low median growth inhibition level of Cu was found for grapevine roots (0.809–3.671 μM). Moreover, Cu toxicity was significantly alleviated by Mg treatment at Mg2+ activity between 0.15 and 2.01 mM. For accumulation and translocation effects, results indicated that competition for binding sites between Cu and Mg occurred for roots; however, Mg and Cu levels in stems and leaves were not affected by solution metals concentration. At Cu concentration less than 1 μM, the translocation of Cu was decreased significantly for the highest Mg treatment; at Cu concentrations greater than 5 μM, no obvious change was observed in leaf TF value between Mg treatments, while an increasing trend of stem TF value was observed with increasing Mg. These results suggest that the toxic effect resulted from metals depend not only on the competition of coexistent cations for plasma membrane surface, but also on the transport and distribution of toxic metals in physiological active sites in plants.