Increasing phosphorus concentration in soil as a possible strategy to overcome Cu excess toxicity symptoms

Excess of copper in soil can be toxic for plants; however, soil P availability seems to insolubilize Cu, improve plant nutrition and mitigate the negative effects of Cu toxicity. The aim of this study was to evaluate the effect of increasing rate of P supply on Cu toxicity in grapevines plants grown on a sandy soil in rhizobox containers. Micro-propagated plants of 1103 Paulsen rootstock were grown according to a factorial experimental design with two factors: copper addition (4 levels: 0, 100, 200, 300 mg kg-1 dw) and phosphorus addition (3 levels: 0, 50 100 mg kg-1 dw) and four replicates. At the end of the trial (100 days after transplanting), plants were destructively harvested and the biomass was evaluated. Cu and P concentration analyses were performed on leaves. At P0, the Cu concentration in leaves decreased as the rate of Cu in soil increased. At P50 it was unaffected by Cu application rate. At P100 leaves Cu concentration increased with the rate of Cu. At Cu0 and at the highest P concentration, Cu in leaves increased at 300 mg Cu kg-1 soil, if compared to the lowest soil Cu addition. A similar trend was observed for P leaf concentration. The biomass of plants declined as a consequence of the increase of Cu concentration in soil, while the increase of soil P availability enhanced plant growth. In conclusion, the increase of P availability mitigates Cu excess symptoms in plants, since it improves plants biomass and leaf nutrient concentration, however, P effect is less pronounced in severe Cu toxicity.