Copper sorption and accumulation by the extraradical mycelium of different Glomus spp. (arbuscular mycorrhizal fungi) isolated from the same polluted soil

The form and localisation of Cu accumulation in the extraradical mycelium (ERM) of three arbuscular mycorrhizal fungi (AMF), isolated from the same polluted soil contaminated with the Cu and Arsenate, was studied. There were differences in the capacity of the ERM of the three AMF to sorb and accumulate Cu. Glomus caledonium BEG133 had a significantly lower Cu-sorption capacity than Glomus mosseae BEG132 and Glomus claroideum BEG134 isolated from the polluted soil as well as an isolate of G. mosseae BEG25 from a non-polluted soil. This was directly related to the cation exchange capacity (CEC) of the ERM of these fungi. Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) linked to an energy dispersive X-ray spectrometer (EDAX) gave more detailed information, showing that the ERM of AMF from the polluted soil was able to accumulate Cu in the mucilaginous outer hyphal wall zone, cell wall and inside the hyphal cytoplasm. The EDAX spectra showed that the accumulated Cu was mainly associated with Fe in the mucilaginous outer hyphal wall zone and in the cell wall. Cu was associated with traces of arsenate inside the cytoplasm of the ERM of Glomus mosseae BEG132 but this was not visible inside the ERM of Glomus caledonium BEG133 or Glomus claroideum BEG134. This work suggests that the ERM of AMF is able to sorb and accumulate Cu, but different tolerance mechanisms exist between the three AMF isolated from the same polluted soil providing further evidence for functional diversity within populations of AMF in soils.     

The Removal of Pb and Cd from Heavily Contaminated Soil in Kayseri,Turkey by a Combined Process of Soil Washing and Electrodeposition

In this study, a combined system of soil washing and electrodeposition was designed to remove Pb (16381±643 mg/kg) and Cd (34347±1310 mg/kg) from contaminated soil. 0.05 M Na₂EDTA was used as a chelating agent for the remediation of soil, taken from the nearby city Kayseri, Turkey. As a result of the batch extraction tests, maximum removals were determined as; at the 20:1 liquid: soil ratio for Pb is 60.7%, for Cd at the 30:1 liquid: soil ratio is 67.4%. An electrochemical treatment was applied to the waste washing solution which appeared to be the second pollutant after the Na₂EDTA extraction from the soil. With extraction tests of Pb and Cd, being transformed from the solid phase to the liquid phase. The electrochemical treatment (electrodeposition), performed in three different potential (6 V, 8 V and 10 V) and maximum removal efficiencies, were found 99.7% and 80.3% at 10 V for Pb and Cd, respectively.

Speciation tests (BCR) were carried out, both before and after the soil washing process, to evaluate the redistribution of metal fraction in the soil. The fraction, associated with the organic substance, was found as 10.67% for Pb and 1.81% for Cd. The metal bioavailability factor increased after soil washing, which indicates that EDTA could enhance the mobility of Pb and Cd.     

Reproductive cycle by histological characterization of the ovary in the butterfly goodeid Ameca splendens from the upper Río Ameca Basin, Mexico

The ovarian cycle was studied in Ameca splendens, a viviparous fish native to western Mexico. Two wild populations living in environments with differential conditions (a small pond adjacent to a reservoir and a spring) were examined to determine whether the conditions these populations are exposed to can elicit differences in the reproductive cycle. The two sites differ from each other with respect to several environmental factors: the spring has clear, oxygen‐rich water while the pond has higher levels of conductivity, hardness and inorganic nitrogen. Six stages of gonadal maturation were identified in A. splendens, based on histological and macroscopic characteristics of the gonad. The relative frequency of gonadic stages at both sites showed two reproductive peaks during the year: from March to May and from September to November. Histologically, ovaries exhibit an asynchronous development in both populations, revealing the existence of a multiple reproductive cycle. Relative mean condition shows organisms are in peak condition (K > 1) at age class 1+ as they recruit to reproduction; K was <1 following the onset of multiple reproduction. The Fulton condition factor shows that the mean condition is slightly higher in the spring population. The relative frequency of gonadal maturation differed between the study sites and is indicative of the plasticity of A. splendens in facing different conditions within the environments it inhabits.     

Present and potential uses of the natural abundance of stable isotopes in plant science, with illustrations from the marine environment

The use of stable isotope natural abundance measurements in plant ecophysiological research is discussed in the context of studies of ¹³C/¹²C ratios in marine plants, with emphasis on the uniqueness of the information given by natural abundance measurements and of the importance of complementary data obtained by other techniques in making full use of the natural abundance data. (1) Inorganic C acquisition and assimilation in marine plants can involve diffusive entry of CO₂, or the occurrence of a CO₂-concentrating mechanism frequently involving active HCO₃^? influx. For diffusive CO₂ entry, the δ¹³C measurements can give unique information on the fractional limitation of photosynthesis by CO₂ transport which, with photosynthetic rate measurements, can be used to compute transport conductances. For active HCO₃^?, influx, the δ¹³C values uniquely permit computation of the ratio of the bidirection fluxes (influx/efflux) which, with photon yield data, can be used to given information on the mechanism of the efflux. The analyses are absolutely dependent on external (non-δ¹³C) data distinguishing between diffusive CO₂ entry and the occurrence of a CO₂ concentrating mechanism. (2) δ¹³C measurements on marine photolithotrophs and on members of other trophic levels collected from the sea can give unique data on food webs, with measurements of δ values for other isotopes and compositional data adding precision to the interpretations. (3) Measurements of in situδ¹³C values for extant marine photolithotrophs, compared with δ¹³C values for ancient atmospheric CO₂, can give unique information on the mechanism of atmospheric CO₂ draw-down at the start of glacials; other information permits more concrete conclusions to be drawn.