Sabina Rossini Oliva

Comparison of Two Wet Digestion Procedures for Multi‐element Analysis of Plant Samples

Two microwave digestion systems for multi‐element analysis of leaves and fruits were compared. Samples were digested by two different methods: 1) with HNO3 (8 mL) and HClO4 (6 mL) using an open microwave system and 2) with HNO3 (5 mL) and H2O2 (3 mL) in a closed microwave system. Total concentrations of aluminum (Al), cadmium (Cd), copper (Cu), chromium (Cr), iron (Fe), leaf (Pb), magnesium (Mg), manganese (Mn), nickel (Ni), and zinc (Zn) were determined in 22 samples by inductively coupled plasma atomic emission spectrometry and by simultaneous inductively coupled plasma mass spectrometry (ICP/AES and ICP/MS). Not statistical differences for Cu, Mn, Mg, Pb, and Zn concentration between the two methods were observed. Trace elements, whose concentration is low, such as Cr and Cd, have to be determinate by ICP/MS. The accuracy of the procedures was acceptable, except for Al, Fe, and Mg using the open microwave system, as the results from certified reference materials were in agreement with certified values.

Selective uptake of major and trace elements in Erica andevalensis, an endemic species to extreme habitats in the Iberian Pyrite Belt

To assess the ecophysiological traits and the phytoremediation potential of the endemic heather Erica andevalensis, we determined the concentrations of major and trace elements in different plant parts and in rizosphere soils from Riotinto mining district (Huelva, Spain). The results showed that E. andevalensis may grow on substrates with very high As, Cu, Fe and Pb concentrations (up to 4114, 1050, 71900 and 15614 microg/g dry weight, respectively), very low availability of macro- and micronutrients and with pH values ranging from 3.3 to 4.9. In these harsh edaphic conditions E. andevalensis selectively absorbed and translocated essential nutrients and excludes potentially phytotoxic elements, which were accumulated in the root epidermis. The concentrations of major and trace elements in E. andevalensis aerial parts from the Riotinto mining district were in the normal range for plants; likewise other Erica species it accumulated Mn and only in a very polluted site we measured leaf concentrations of As and Pb within the excessive or toxic limits for plants. Differently from previous studies, which emphasized the soil pH and bioavailability of phytotoxic elements as the main stress factors, this study showed that in the Riotinto region, E. andevalensis can tolerate wide range of pH and toxic element concentrations; the harshest environments colonized by monospecific patches of this species were characterized above all by very low availability of nutrients. The extraordinary capability to adapt to these extreme habitats made E. andevalensis a priority species to promote the phytostabilization and the development of a self-sustaining vegetative cover on Riotinto mine tailings.

Effects of silicon on copper toxicity in Erica andevalensis Cabezudo and Rivera: a potential species to remediate contaminated soils

The influence of silicon on responses to copper excess was studied in plants of Erica andevalensis. Plantlets were grown in nutrient solutions containing two Cu (1 and 500 µM) and three Si concentrations (0, 0.5 and 1 mM). Plant growth, water content, and mineral nutrient concentration were determined. Plants grown with 500 µM Cu showed differences in growth and shoot water content depending on Si supply. The addition of 1 mM Si in high-Cu nutrient solutions significantly improved plant growth and reduced water loss preventing plant death related to Cu-excess. Silicon supply reduced significantly leaf Cu concentration (up to 32%) and increased Cu concentration in roots. Phytoliths isolated from leaves were analysed by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. Such phytoliths consisted in silica deposits associated with Cu and other elements (K, Ca, P). Improvement by Si of Cu tolerance in E. andevalensis was clearly related to the inhibition of Cu upward transport. The leaf phytoliths formed in Si-treated plants might have some contribution to tolerance by Cu immobilisation and inactivation.

Influence of Washing on Metal Concentrations in Leaf Tissue

Abstract The possible effect of washing leaf tissue on metal concentrations was studied in four ornamental plants (Nerium oleander L., Ficus microcarpa L. f., Ligustrum lucidum Ait. f., and Duranta repens L.). Elements determined were aluminum (Al), barium (Ba), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), magnesium (Mg), nickel (Ni), lead (Pb), zinc (Zn), and vanadium (V). A portion of each studied sample was washed with distilled water, while the remainder of the sample was not washed. Significant differences in metal concentration between washed and unwashed samples were observed in some species. Washing effects differed with species and contaminants. The results are discussed in relation to leaf characteristics and to contaminant chemical properties.

Effect of Chemical and Physical Treatments on Seed Germination of Erica australis

We studied the germination of Erica australis seeds and their responses to different treatments (high temperature, acidic condition, cold stratification, gibberellic acid applications). Germination was very low in untreated seeds (3%) and required approximately one month to start, but increased in all the treatments tested, reaching a value of 100% when seeds were treated with gibberellic acid (25 ppm). Exposure to heat and to low pH promotes germination and reduces time to germinate, which indicates that germination is related to passage of fire and to soil pH. Germination of this species is also correlated with wet and cold conditions and dormancy can be classified as being of the physiological type.

Active proton efflux, nutrient retention and boron-bridging of pectin are related to greater tolerance of proton toxicity in the roots of two Erica species

Background and aims Tolerance to soil acidity was studied in two species of Ericaceae that grow in mine-contaminated soils (S Portugal, SW Spain) to find out if there are interspecific variations in H+ tolerance which might be related to their particular location. Methods Tolerance to H+ toxicity was tested in nutrient solutions using seeds collected in SW Spain. Plant growth and nutrient contents in leaves, stems and roots were determined. Viability tests and proton exchange were studied in roots exposed, short-term, to acidic conditions. Membrane ATPase activity and the cell-wall pectic polysaccharide domain rhamnogalacturonan-II (RG-II) were analysed to find out interspecific differences. Results Variation in survival, growth and mineral composition was found between species. The H+-tolerant species (Erica andevalensis) showed greater concentration of nutrients than E. australis. Very low pH (pH 2) produced a significant loss of root nutrients (K, P, Mg) in the sensitive species. Root ATPase activity was slightly higher in the tolerant species with a correspondingly greater H+ efflux capacity. In both species, the great majority of the RG-II domains were in their boron-bridged dimeric form. However, shifting to a medium of pH 2 caused some of the boron bridges to break in the sensitive species. Conclusions Variation in elements linked to the cell wall-membrane complex and the stability of their components (RG-II, H+-ATPases) are crucial for acid stress tolerance. Thus, by maintaining root cell structure, active proton efflux avoided toxic H+ build-up in the cytoplasm and supported greater nutrient acquisition in H+-tolerant species.