Microspectroscopy reveals dust-derived apatite grains in acidic, highly-weathered Hawaiian soils

Dust deposition is an important source of phosphorus (P) to many ecosystems. However, there is little evidence of dust-derived P-containing minerals in soils. Here we studied P forms along a well-described climatic gradient on Hawaii, which is also a dust deposition gradient. Soil mineralogy and soil P forms from six sites along the climatic gradient were analyzed with bulk (X-ray diffraction and P K-edge X-ray absorption near edge structure) and microscale (X-ray fluorescence, P K-edge X-ray absorption near edge structure, and Raman) analysis methods. In the wettest soils, apatite grains ranging from 5 to 30 µm in size were co-located at the micro-scale with quartz, a known continental dust indicator suggesting recent atmospheric deposition. In addition to co-location with quartz, further evidence of dust-derived P included backward trajectory modeling indicating that dust particles could be brought to Hawaii from the major global dust-loading areas in central Asia and northern Africa. Although it is not certain whether the individual observed apatite grains were derived from long-distance transport of dust, or from local dust sources such as volcanic ash or windblown fertilizer, these observations offer direct evidence that P-containing minerals have reached surface layers of highly-weathered grassland soils through atmospheric deposition

Germination and early development of Brassica napus and Brachypodium distachyon growth with Zn, Cr (VI), As (V) or Cd: Preliminary results

Phytoremediation could reduce heavy metal bioavailability in soils and obtain renewable energy from lands useless. Some fast-growing, high biomass crop species are known to display a significant heavy metal tolerance, particularly those from the genus Brassica. These species could be phytoremediator candidates for recuperate polluted soils with heavy metals. Brachypodium distachyon has also been recently proposed as a model species to develop bioenergy. However, there are no experiments about the tolerance of this plant to metals. The present work reports data concerning the ability of Brachypodium distachyon and Brassica napus seeds to germinate and grow in media containing different doses of Cd, Cr, As and Zn, in order to evaluate their use as energy crops in polluted sites. Biomass reduction and length decreasing were observed as consequence on increasing metal doses in both species, but the effect was different attending to metal and species. The maximum toxicity level was found in plants treated with Cr (VI). Exposures of 30 mg L−1 of Cd and As (V) reduced the shoot elongation by 50% in both species, while root was affected by lower doses than 30 mg L-1. Concentrations of Zn affected neither length, nor biomass of B. distachyon, but shoot and root elongation of B. napus were reduced from the lowest dose of Zn

Effect of genotype, Cr(III) and Cr(VI) on plant growth and micronutrient status in Silene vulgaris (Moench)

Chromium released into the environment from industrial activities has become an important environmental concern. Silene vulgaris has been proven to be tolerant to many heavy metals, so it is considered an interesting species in the revegetation and restoration of polluted soils, but no information is available about its response to Cr. The objective of this work was to study uptake and influence on plant growth of Cr(III) and Cr(VI) in six genotypes (four hermaphrodites and two females) of S. vulgaris from different sites of Madrid (Spain). Plants were treated for 12 days with 60 µM of Cr(III) or Cr(VI) in semihydroponics. Dry weights, soil-plant analysis development values (SPAD) reading with chlorophylls and micronutrient and total Cr concentrations were determined. Metal uptake was higher in presence of Cr(VI) than of Cr(III) and poorly translocated to the shoots. In both cases S. vulgaris did not show visual toxicity symptoms, biomass reduction, or differences among SPAD values as consequence of Cr additions. However genotypes SV36 and SV38 showed Fe and Mn imbalance. This is the first report on the relatively good performance of hermaphrodite and female S. vulgaris genotypes in Cr uptake and physiological traits, but further studies will be necessary to elucidate the mechanisms by which the gender may influence these variables. S. vulgaris presented high diversity at genotypic level; the treatment with hexavalent Cr increased the differences among genotypes so the use of cuttings from an homogeneous genotype seems to be an adequate method for the study of this species

Effect of genotype, Cr(III) and Cr(VI) on plant growth and micronutrient status in Silene vulgaris (Moench)

Chromium released into the environment from industrial activities has become an important environmental concern. Silene vulgaris has been proven to be tolerant to many heavy metals, so it is considered an interesting species in the revegetation and restoration of polluted soils, but no information is available about its response to Cr. The objective of this work was to study uptake and influence on plant growth of Cr(III) and Cr(VI) in six genotypes (four hermaphrodites and two females) of S. vulgaris from different sites of Madrid (Spain). Plants were treated for 12 days with 60 µM of Cr(III) or Cr(VI) in semihydroponics. Dry weights, soil-plant analysis development values (SPAD) reading with chlorophylls and micronutrient and total Cr concentrations were determined. Metal uptake was higher in presence of Cr(VI) than of Cr(III) and poorly translocated to the shoots. In both cases S. vulgaris did not show visual toxicity symptoms, biomass reduction, or differences among SPAD values as consequence of Cr additions. However genotypes SV36 and SV38 showed Fe and Mn imbalance. This is the first report on the relatively good performance of hermaphrodite and female S. vulgaris genotypes in Cr uptake and physiological traits, but further studies will be necessary to elucidate the mechanisms by which the gender may influence these variables. S. vulgaris presented high diversity at genotypic level; the treatment with hexavalent Cr increased the differences among genotypes so the use of cuttings from an homogeneous genotype seems to be an adequate method for the study of this species