Physiological responses of soybean (Glycine max (L.) Merrill) cultivars to copper excess.

Successive applications of copper fungicides on vines have resulted in increased copper content in vineyard soils over the years. This high copper content has affected the growth of young vines in eradicated vineyards. Thus, the cultivation of annual species for a few years is an alternative to copper phytostabilization, because it would be a good way to decrease copper availability to plants. The aim of this study was to evaluate the physiological responses of different soybean cultivars to copper concentration increase. Four different soybean cultivars were grown under three copper concentrations: 0.5, 20 and 40 µM in nutrient solution. The main outcomes of this study were: i) Cultivar M 6410 IPRO recorded the highest photosynthetic rate when plants were exposed to 40 µM of copper in the nutrient solution; ii) plants in cultivar M 6410 IPRO accumulated large copper concentrations in their roots although did not decrease the root dry mass, possibly due to the higher superoxide dismutase activity; iii) cultivar DM 5958 RSF IPRO recorded drastically reduced photosynthetic rate and dry mass production due to copper excess. We conclude that each cultivar responded differently to the excess of copper, but none of them showed tolerance to it.

Soil amendment as a strategy for the growth of young vines when replanting vineyards in soils with high copper content.

Soil contamination with copper (Cu)-based agrochemicals used in vineyards for pest control is a growing problem. In this context, the application of soil amendment to limit Cu toxicity, especially for young plants after the replanting of vineyards, has been a concern for winemakers. Therefore, the aim of this study was to evaluate how different amendments can contribute to the decrease in Cu availability in areas vocated to viticulture. Furthermore, the aim was to evaluate to the effect of Cu on the biochemical and physiological changes in the development of the young vine plants, both at the shoot and the root level. Vine plants were grown in a greenhouse using a Typic Hapludalf soil characterized by 87.5 mg of Cu kg-1 (control). Three different amendments were applied to the soil: limestone (3 Mg ha-1), calcium silicate (3 Mg ha-1) and vermicompost (30 g of C kg-1). The amendment with vermicompost and calcium silicate caused a significant alkalization of the soil solution. Moreover, specifically for the treatment with vermicompost, the levels of Cu2+ in the soil solution were consistently diminished with a clear benefit for plants (+89% biomass accumulation at the shoot level). In addition, this soil amendment led to a higher photosynthetic rate, lower superoxide dismutase (SOD, EC 1.15.1.1) and guaiacol peroxidase (POD, EC 1.11.1.7) activity and a higher percentage of fine roots with diameter between 0 < L ≥ 0.2 mm (particularly active in water and nutrient acquisition). In conclusion, results showed that vermicompost effectively reduced Cu phytotoxicityin young vines grown in soils with high Cu contents. Furthermore, this amendment might be an asset in enhancing the availability of other important micronutrients such as iron.