Strategies in a metallophyte species to cope with manganese excess

The effect of exposure to high Mn concentration was studied in a metallophyte species, Erica andevalensis, using hydroponic cultures with a range of Mn concentrations (0.06, 100, 300, 500, and 700 mg L-1). At harvest, biomass production, element uptake, and biochemical indicators of metal stress (leaf pigments, organic acids, amino acids, phenols, and activities of catalase, peroxidase, superoxide dismutase) were determined in leaves and roots. Increasing Mn concentrations led to a decrease in biomass accumulation, and tip leaves chlorosis was the only toxicity symptom detected. In a similar way, photosynthetic pigments (chlorophylls a and b, and carotenoids) were affected by high Mn levels. Among organic acids, malate and oxalate contents in roots showed a significant increase at the highest Mn concentration, while in leaves, Mn led to an increasing trend in citrate and malate contents. An increase of Mn also induced an increase in superoxide dismutase activity in roots and catalase activity in leaves. As well, significant changes in free amino acids were induced by Mn concentrations higher than 300 mg L-1, especially in roots. No significant changes in phenolic compounds were observed in the leaves, but root phenolics were significantly increased by increasing Mn concentrations in treatments. When Fe supply was increased 10 and 20 times (7–14 mg Fe L-1 as Fe-EDDHA) in the nutrient solutions at the highest Mn concentration (700 mg Mn L-1), it led to significant increases in photosynthetic pigments and biomass accumulation. Manganese was mostly accumulated in the roots, and the species was essentially a Mn excluder. However, considering the high leaf Mn concentration recorded without toxicity symptoms, E. andevalensis might be rated as a Mn-tolerant speciesinfo:eu-repo/semantics/publishedVersio

Accumulation and in vivo tissue distribution of pollutant elements in Erica andevalensis

Erica andevalensis is an endemic shrub from an area in the southwest of Spain (Andalucia) characterized by acidic and contaminated soils. Scanning electron microscopy (SEM) of samples after conventional or cryo-fixation preparation protocols was used for morphological and anatomical studies. SEM coupled with EDX-analysis was employed to localise and quantify different elements within plant parts (leaves, stems and roots) in samples collected in the field. Morphological studies revealed that the species has typical adaptive structures to drought-stress such as rolled needle-like leaves, sunken stomata and a thick waxy cuticle on the upper epidermis. Roots were associated with fungi which formed intra and extra-cellular mycelia. The SEM studies showed that Cu was not sequestrated into the root tissues and was uniformly distributed in leaf tissues. Meanwhile, Pb was only localised within epidermal root tissues which indicates that its sequestration in an external matrix might represent a tolerance mechanism in this species. Iron was uniformly distributed throughout the leaves, while in roots it was predominantly retained on the epidermal cell walls. The exclusion and tolerance mechanisms adopted by this species to survive in mining areas indicate that it can be used successfully in the re-vegetation of contaminated areas.Peer Reviewe

Germination responses of Erica andevalensis to different chemical and physical treatments

7 pages, 4 figures, 1 table.-- Available online Aug 12, 2008.Erica andevalensis Cabezudo & Rivera is a threatened edaphic endemic species of Andalusia (SW Spain). Under natural conditions, the plants produce a very large number of small seeds (0.3–0.4 mm) but very few seedlings survive. Different treatments (high temperature, cold pre-treatment, nitrogen salts, and gibberellic acid applications) were tested to assess germination patterns in different populations and to determinate the most favorable conditions for germination. Gibberellic acid was provided in five different concentrations from 0 to 400 ppm GA3, while nitrogen was applied as 10 mM of either KNO3 or NH4NO3. The effect of pH on germination was also tested. The species always showed a low germination rate (6.50–22%) that was not stimulated either by 1 or 4 months in dry cold pre-treatment, nitrogen application, acid pH medium, or by high temperature (80°C for 10 min); although gibberellic acid application (100–400 ppm) significantly enhanced germination. The highest percentage of germination (41.6%) was achieved with a mean germination time to start germination (t-0) of 7.6 ± 0.54 days when the seeds were subjected to 400 ppm gibberellic acid treatment. The population origin did not have a significant effect on germination percentage.The present research was supported in part by the Spanish Ministry of Science and Education (CGL2006/02860) and in part by Fundación Areces (Proyect title: Mecanismos de resistencia a metales pesados en especies significativas de la cuenca minera de Riotinto).Peer reviewe

Tolerance to high Zn in the metallophyte Erica andevalensis Cabezudo & Rivera

The tolerance to high Zn was studied in the metallophyte Erica andevalensis Cabezudo & Rivera grown in nutrient solutions at different Zn concentrations (5, 500, 1,000, 1,500 and 2,000 οM Zn). Plant growth and nutrient uptake were determined. Metabolic changes were assessed by the analysis of peroxidase activity, organic metabolites related to metal chelation (amino acids, organic acids (malate, citrate) or protection (polyamines). While plants tolerated up to 1,500 lM Zn, despite presenting of low growth rates, the concentration of 2,000 lM Zn was toxic producing high mortality rates. Roots accumulated high Zn concentration (11,971 mg/kg) at 1,500 lM external Zn) apparently avoiding metal transfer into shoots. After 30 days of treatment with high Zn (1,000 and 1,500 lM Zn), the leaves accumulated high levels of glutamine. Shortterm treatment with 500 lM Zn, significantly increased the concentration of asparagine and glutamine in roots. Citrate concentration was also considerably increased when exposing roots to Zn excess. Metal immobilization in the root system, low interference with the uptake of nutrients and an increased production of putative organic ligands (amino acids, citrate) might have provided the Zn tolerance displayed by Erica andevalensis.This research was supported by Spanish Ministry of Science and Education (MEC) (CGL2006-1,418 and José Castillejo Program) and Ramón Areces Foundation.Peer Reviewe

A review of hazardous elements tolerance in a metallophyte model species: Erica andevalensis

9 páginas.-- 5 figuras.-- 2 tablas.-- referenciasAs a result of mining activities large portions of land have been degraded. In this work, different tolerance/resistance mechanisms of Erica andevalensis Cabezudo y Rivera, which allow thriving and growing in soils from mine areas enriched with potentially toxic elements are reported. Different strategies were identified in E. andevalensis to tolerate high concentrations of metal(loid)s in soils through field and laboratory studies. The response of this species to high concentrations of hazardous elements varies according to the element. Experimental evidence for E. andevalensis adaptation to polluted soils/sediments and the role of other chemical elements (e.g. silicon) to enhance metal(loid)s tolerance is described. The species acts as an excluder for almost all elements and its tolerance to the harsh environments is due to complex mechanisms that include defense and avoidance.This research was supported by Spanish Ministry of Science and Education (MEC) (CGL2006-1418 and José Castillejo Program) and Ramón Areces Foundation. This work was also developed in the scope of the projects LEAF (Linking Landscape, Environment, Agriculture and Food Research Centre) – Instituto Superior de Agronomia, Universidade de Lisboa (FCT-UID/AGR/04129/2013), financed by the FCT/MEC through national funds and co-financed by the FEDER within the PT2020 Partnership Agreement.Peer reviewe

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 M) and three Si concentrations (0, 0.5 and 1 mM). Plant growth, water content, and mineral nutrient concentration were determined. Plants grown with 500 M 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.Peer Reviewe

EDTA assisted phytoextraction of metals using Erica andevalensis

Phytoremediation techniques applying chelating agents are frequently used to increase the bioavailability of heavy metals. These procedures may increase plant metal uptake and enhance soil-cleaning processes. Such techniques are particularly useful in cases of widespread pollution limited to the surface soil layer, as it occurs in abandoned mine sites. Our study was designed to explore the use of Erica andevalensis jointly with EDTA application to enhance phytoextraction of metals in soils of an abandoned mine area (Riotinto, Spain). Such soils are acidic (pH 3), poor in plant essential elements and have Cd and Pb contents above the toxicity threshold. Plants were grown in soil irrigated with EDTA solutions at different concentrations (1, 3 and 5 mM) or in EDTA-extracted soil solutions during three weeks. The metal concentrations in plants cultivated in soil+EDTA were similar to those in control conditions (without EDTA) indicating that EDTA was not able to promote metal uptake in Erica plants. In addition, EDTA caused significant reduction in plant biomass suggesting phytotoxic effects, however, no visible damages were observed on plants. On the other hand, plants grown in EDTA-extracted soil solutions showed severe toxicity symptoms. These results indicate that the strategy of EDTA-assisted phytoextraction does not work with Erica andevalensis. However, for its capability to colonize mine tailings, this species is good candidate for phytostabilization in mining districts

Phytostabilization potential of Erica australis L. and Nerium oleander L.: a comparative study in the Riotinto mining area (SW Spain)

Phytostabilization is a green, cost-effective technique for mine rehabilitation and ecological restoration. In this study, the phytostabilization capacity of Erica australis L. and Nerium oleander L. was assessed in the climatic and geochemical context of the Riotinto mining district, southwestern Spain, where both plant species colonize harsh substrates of mine wastes and contaminated river banks. In addition to tolerating extreme acidic conditions (up to pH 3.36 for E. australis), both species were found to grow on substrates very poor in bioavailable nutrients (e.g., N and P) and highly enriched with potentially phytotoxic elements (e.g., Cu, Cd, Pb, S). The selective root absorption of essential elements and the sequestration of potentially toxic elements in the root cortex are the main adaptations that allow the studied species to cope in very limiting edaphic environments. Being capable of a tight elemental homeostatic control and tolerating extreme acidic conditions, E. australis is the best candidate for use in phytostabilization programs, ideally to promote early stages of colonization, improve physical and chemical conditions of substrates and favor the establishing of less tolerant species, such as N. oleander.