The role of root organic acids in the tolerance of Festuca rubra to zinc,lead and cadmium

Abstract

Festuca rubra L. plants are pseudometallophytes colonizing abandoned Pb/Zn mine areas, successfully employed in phytostabilization. To study the contribution of low-molecular weight organic acids to metal tolerance, F. rubra plants were grown for three months in hydroponics with Cd (1.8, 18 and 36 µmol?L^?1), Pb (50, 250 and 500?µmol?L^?1) and Zn (0.3, 3 and 6?mmol?L^?1), separately, and in ternary combination (18?µmol?L^?1 Cd + 250?µmol?L^?1 Pb + 0.3?mmol?L^?1 Zn). The roots retained most of the metals but their distribution from shoot to root was altered when the plants were treated with the ternary combination. The main organic acids in roots were citrate and malate. At the lowest concentrations, the metals caused small reductions in biomass, had no effects on photosynthetic pigments nor on malondialdehyde, but led to increases in root organic acids. At higher concentrations, phytotoxic responses were observed, associated with a decline of citrate and malate in the roots.     

Understanding the distribution of cattle production systems in the South American Chaco

ABSTRACT

Impacts of cattle production vary among different production systems, but data on their distribution is scarce for most world regions. In this work, we combine datasets on cattle vaccination locations and land cover in a regression framework to define and map major cattle production systems in the Argentinean Dry Chaco. We also explore how cattle occurrence relates to spatial determinants. Results indicate that the region harbors about 5.5 million heads. Cattle density was mainly described by the share of pasture (69.9%), cropland (28.1%) and aridity (23.8%). We identified 12-major cattle production systems: six cow-calf, three whole-cycle, and three fattening systems. Of these, four systems had high woodland cover (>85%). Data generated is available in a website. Understanding the distribution of cattle production systems is important to assess the environmental impacts of beef production at broad scales. Integrating vaccination data with land-cover information provides a promising avenue to identify livestock systems.     

Genetic mating system and timing of extra-pair fertilizations in the Kentish plover

It is still unclear why females in many bird species pursue extra-pair copulations. Current hypotheses focus mainly on indirect benefits such as obtaining particular good genes for their offspring or maximizing genetic compatibility between themselves and the father of their offspring. Supporting the latter, a recent study of shorebirds suggests that extra-pair matings may function to avoid the negative effects of genetic similarity between mates. Here, we further investigate genetic parentage in the Kentish plover, Charadrius alexandrinus, a shorebird with a highly variable social mating system. DNA fingerprinting revealed that most pairs were genetically monogamous: 7.9% of the broods (7/89) contained extra-pair young, comprising 3.9% of all chicks (9/229). These cases represented, however, three alternative reproductive behaviors: extra-pair paternity, quasi-parasitism (extra-pair maternity) and intraspecific brood parasitism. This is the first study showing the occurrence of all three behaviors in one shorebird species. We also found that extra-pair fertilizations (extra-pair paternity and quasi-parasitism) were more frequent later in the breeding season. There was no consistent relationship between genetic similarity of mates and laying date; the pattern, as well as the degree of genetic similarity, differed among breeding sites within the study population.Communicated by M. Webster     

Forest cover dynamics in the Selva Maya of Central and Southern Quintana Roo,Mexico: deforestation or degradation?

ABSTRACT

Forest cover dynamics (1993-2018) was assessed in two regions on the Yucatan Peninsula: Zona Maya (ZM), 67% indigenous with shifting cultivation and community forestry; and Bacalar–Rio Hondo (BRH), mainly commercial agriculture and pastureland. Degradation (12,915 ha y^?1) exceeded deforestation (5882 ha y^?1) and was worse in BRH. In BRH there was a net forest loss (?1.6% y^?1) associated with pastureland and commercial agriculture. In ZM, mature forest recovery (1.4% y^?1) and dynamic forest cover (continuous loss and gain) were associated with shifting cultivation. Changes were more intense during 2011–2018 and gains of mature forest in ZM and deforested areas in BRH targeted secondary vegetation. Fragments of mature and secondary vegetation decreased, and connectivity improved in ZM, but opposite trends occurred in BRH. Reporting and monitoring deforestation using Global Forest Watch data is inadequate since 62% of forest cover loss represent degrading or recovering forest cover.     

Determination of selected neonicotinoid insecticides by liquid chromatography with thermal lens spectrometric detection

We studied the analysis of trace amounts of neonicotinoid insecticides by liquid chromatography coupled with a thermal lens spectrometric detector (TLS). This multi-residue analysis method is based on the reversed phase separation on C₁₈ column, isocratic elution and collinear dual beam TLS detection. The insecticides thiamethoxam, imidacloprid, acetamiprid and thiacloprid were detected with retention times of 4.4, 5.7, 6.5 and 8.5 min and limits of quantifications of 50, 89, 10, and 25 μg/L, respectively. The retention times agreed well with those obtained by the same chromatographic method but using a diode-array detector (DAD). The limits of quantifications for imidacloprid were identical in both techniques. However, the limits of quantifications for thiamethoxam, acetamiprid and thiacloprid were up to 8.5 times lower using the TLS detector compared to the diode-array detector. The applicability of the developed procedure was tested on spiked river water and potato samples.     

Chemical availability of arsenic and antimony in industrial soils

Total concentrations and extractable fractionations of As and Sb were determined in soil samples from former mining sites in Scotland and Italy. Pseudo-total levels of As and Sb in the sample were between 50–17,428 mg/kg and 10–1,187 mg/kg (Scotland), and 16–691 mg/kg and 1.63–11.44 mg/kg (Italy). Between 0.001–0.63% and <0.001−8.82% of the total soil As and Sb, were extractable using, a single extraction bioavailability estimate. Data from an As-specific extraction procedure revealed that up to 60% of As was associated to amorphous Fe-Al oxyhydroxide phase in all soils. A non-specific-sequential extraction test also showed As to be strongly associated with Fe (and Al) oxyhydroxides at both locations. In the case of Sb, in addition to the crystalline Fe-oxide bound Sb the Al-silicate phase also appeared to be significant. At both sites Sb appears to be chemically more accessible than As with consistent availability despite the varied origin and host soil properties.     

Mercury in surface sediments and benthic organisms from Guaymas Bay,east coast of the Gulf of California

In order to know the concentration of mercury in surface sediments, macroalgae and clams from Guaymas Bay, Mexico, 20 surface sediment samples and several individuals of Codium amplivesciculatum (3), Enteromorpha clathrata (4), Gracilaria subsecundata (2), Ulva lactuca (2), Chione subrugosa (80) and Crassostrea gigas (40) were collected and their Hg concentration was measured by a cold vapor Hg analyzer, after acid digestion. In addition, granulometric analysis and quantification of total organic carbon, aluminum, iron and manganese contents in sediments were performed. A Pearsons correlation matrix was determined and, the enrichment factor, the geoaccumulation index and the biota-sediment accumulation factor were calculated. Mercury concentrations in sediments ranged from 0.3 to 2.3 μg g⁻¹, with the central and northern portions showing the highest values. Macroalgae had a content of Hg that oscillated from 0.058 to 0.134 μg g⁻¹, while the average concentrations of this metal for clams and oysters were 0.063 and 0.230 μg g⁻¹, respectively. A clear effect of Guaymas City and the anthropogenic activities carried out around the Guaymas Bay has been observed and the enrichment factor and the geochemical index suggest that sediments from this coastal ecosystem are moderately to strongly contaminated with Hg. However, according to the figure of the maximum human consumption of Hg per week recommended by the World Health Organization, people can ingest clams without risk to their health.     

Unstable flow, magma mixing and magma-rock deformation in a deep-seated conduit: the Gil-Márquez Complex, south-west Spain

The Gil-Márquez Complex is an exceptional outcrop of plutonic rocks ranging in composition from diorites to granites emplaced into Devonian terrigenous metasediments of the southernmost part of the Hercynian basement of Iberia. A combined study of this complex, including field geology, petrology, structural geology and geochemistry, reveals that it represents an ancient conduit of magma transport through the continental crust. This conduit allowed the intrusion of magmas of contrasted compositions. Two end-members and several hybrids are identified. The first end-member is a biotite granite and the second is a basaltic magma generated by partial melting of a depleted-mantle source. Both magmas rose through a common channel in which favorable conditions for unstable flow and magma mixing occurred. The observed relations in the Gil-Márquez Complex show that mixing in conduits may be an important mechanism for producing homogeneous hybrid magmas.     

Discriminant analysis for assessing the value of amniotic fluid microvillar enzymes in the prenatal diagnosis of cystic fibrosis

We have analysed the sensitivity, specificity, and reliability of biochemical diagnosis based on microvillar membrane enzyme assay and using discriminant analysis in amniotic fluid samples obtained from 54 pregnancies at high risk for cystic fibrosis and 125 normal pregnancies. Our results show that amniotic fluid trehalase, alkaline phosphatase, alkaline phosphatase isoenzymes and gamma-glutamyltransferase enzyme activities measured during 16–20 gestational weeks, in spite of their non-specificity for cystic fibrosis, have a very good predictive value for fetal cystic fibrosis or exclude the possibility of the disease. Overall enzyme activity analysis provided over 90 per cent reliability of the method.