Photosynthesis and growth of young grapevines intercropped with native grasses in soils contaminated with copper

Physiological and biochemical characterization of copper-toxicity tolerance mechanism in grass species native to Pampa Biome and Atlantic Forest for use in phytoremediation

Orchards and vineyards account for significant copper (Cu) accumulation in the soil due to frequent Cu fungicide applications to control leaf diseases. Although grass species are distributed in these areas likely because of their physiological mechanisms to combat Cu toxicity-related stress, the aim of the present study is to identify grass species presenting biochemical-physiological responses that feature adaptive Cu toxicity tolerance mechanisms. Three grass species native to the Pampa and Atlantic Forest biomes (Paspalum notatum, P. plicatulum, and P. urvillei) and an exotic species (Cynodon dactylon) were tested. Plants were cultivated in pots filled with 4 kg of typic Hapludalf soil, under two Cu availability, control, and toxicity conditions (80 mg Cu kg soil^-1). Photosynthetic parameters, relative growth rate, root dry matter, shoot dry matter, the activity of stress-fighting enzymes (superoxide dismutase and guaiacol peroxidase), root biometry, soluble organic carbon, soil pH, and electrical conductivity were evaluated. P. notatum and P. urvillei have physiological characteristics that allow high translocation factor and Cu accumulation in the root and shoot, and it allows their use in phytoremediation processes due to (1) greater activity of stress-fighting enzymes such as POD in the shoot; (2) to larger diameter roots, which allow greater Cu complexation in them - they are lesser sensitive to stress caused by Cu than the other species; and (3) greater soluble organic carbon exudation in the rhizosphere than species P. plicatulum and C. dactylon, which can complex Cu²⁺ and reduce the presence of forms toxic to plants.

Identification and phytoremediation potential of spontaneous species in vineyard soils contaminated with copper

Copper (Cu) contents in vineyard soils due to the application of cupric fungicides cause changes in the native covering flora. Under these conditions, the surviving individuals accumulate the metal in and decrease its availability in the soil, reducing the potential toxicity to grapevine. We have identified spontaneous plant species and their phytoremediation potential from vineyards of Isabella (Vitis labrusca) on two distinct soil types (Inceptisol and Entisol) contaminated with Cu. The results demonstrated that wild species displayed higher Cu contents in the roots than in the shoot, but had low bioaccumulation potential. During summer, the plants were unable to extract and stabilize the metal, although during the winter, Lolium multiflorum, Cyperus compressus and Chrysanthemum leucanthemum demonstrated phytostabilization potential. Among the investigated species, dry matter production and Cu accumulation by Lolium multiflorum indicated that the species is effective to decrease Cu availability in the soil.

Tolerance and phytoremediation potential of grass species native to South American grasslands to copper-contaminated soils

Grass species native to South American can have mechanisms to tolerate copper (Cu) excess, which improves their use to phytoremediate Cu-contaminated soils . The aims of the present study are to assess the tolerance of grass species native to South American grasslands to copper-contaminated soils, as well as their adaptive responses under high Cu-stressed condition and to identify native grass species presenting the highest potential to be used for phytoremediation purposes. Soil samples were air-dried and their acidity, phosphorus and potassium levels were corrected, and the samples were incubated. Three Cu levels were used in the experiment: natural (Dose 0), with added of 40 mg kg^-1 of Cu and with added of 80 mg kg^-1 of Cu. Three Axonopus affinis, Paspalum notatum and Paspalum plicatulum seedlings were transferred to 5-L pots filled with soil in August and grown for 121 days. Soil solution was collected during cultivation with the aid of Rhizon lysimeters. Main concentrations of cations and anions, dissolved organic carbon and pH in the soil solution were analyzed and the ionic speciation was carried out. Cu toxicity impaired the growth of grass species native to South America, since Cu excess led to both changes in root morphology and nutritional unbalance. Among all assessed native species, Paspalum plicatulum was the one presenting the greatest potential to phytostabilize in Cu-contaminated soils, since it mainly accumulates Cu absorbed in the roots; therefore, its intercropping with grapevines is can be beneficial in Cu-contaminated soils.

Plasmopara viticola infection affects mineral elements allocation and distribution in Vitis vinifera leaves

Plasmopara viticola is one of the most important pathogens infecting Vitis vinifera plants. The interactions among P. viticola and both susceptible and resistant grapevine plants have been extensively characterised, at transcriptomic, proteomic and metabolomic levels. However, the involvement of plants ionome in the response against the pathogen has been completely neglected so far. Therefore, this study was aimed at investigating the possible role of leaf ionomic modulation during compatible and incompatible interactions between P. viticola and grapevine plants. In susceptible cultivars, a dramatic redistribution of mineral elements has been observed, thus uncovering a possible role for mineral nutrients in the response against pathogens. On the contrary, the resistant cultivars did not present substantial rearrangement of mineral elements at leaf level, except for manganese (Mn) and iron (Fe). This might demonstrate that, resistant cultivars, albeit expressing the resistance gene, still exploit a pathogen response mechanism based on the local increase in the concentration of microelements, which are involved in the synthesis of secondary metabolites and reactive oxygen species. Moreover, these data also highlight the link between the mineral nutrition and plants' response to pathogens, further stressing that appropriate fertilization strategies can be fundamental for the expression of response mechanisms against pathogens.

Iron fertilization to enhance tolerance mechanisms to copper toxicity of ryegrass plants used as cover crop in vineyards

Ryegrass (Lolium perenne L.) is a plant species that can express mechanisms of tolerance to copper (Cu) toxicity. Therefore, the agronomical approach of intercropping system with ryegrass may represent a promising tool to limit the onset of Cu toxicity symptoms in the other intercropped plants species, particularly when an inadequate nutrient availability like iron (Fe) shortage is also concurrently present. This study aimed at assessing the mechanisms involved in the mitigation of Cu phytotoxicity and the stress effects on plant growth, root morphology and nutrition of ryegrass fertilized with two different Fe sources. To this purpose, seedlings of ryegrass were hydroponically grown for 14 days in controlled conditions with 4 different levels of Cu (0.2, 5.0, 25 and 50 μM) and with either 100 μM Fe-EDDHA or Fe-EDTA. Results show that high levels of Cu availability enhanced the root content of organic anions as well as the root exudation. Different Fe fertilizations at the condition of 50 μM Cu induced changes in root phenolic compounds, citrate and fumarate contents and the exudation pattern of phenolic compounds. Differences in plant growth were not observed between the two Fe sources, although Cu concentration in plant tissue fed with Fe-EDTA was lower in the condition of 50 μM Cu. The enhanced root exudation of Cu-complexing organic compounds (including phenolics) in ryegrass plants when exposed to excessive Cu availability could be at the basis of the ameliorated edaphic rhizosphere conditions (lower Cu availability). For this reason, from the agronomical point of view ryegrass plants used in intercropping systems with crops like vine plants could represent a promising strategy to control Cu toxicity in vineyard soils. Further studies under the field conditions must be taken to support present findings.