Characterization of selenium-enriched wheat by agronomic biofortification.

Agronomic biofortification of staple crops is an effective way to enhance their contents in essential nutrients up the food chain, with a view to correcting for their deficiencies in animal or human status. Selenium (Se) is one such case, for its uneven distribution in the continental crust and, therefore, in agricultural lands easily translates into substantial variation in nutritional intakes. Cereals are far from being the main sources of Se on a content basis, but they are likely the major contributors to intake on a dietary basis. To assess their potential to assimilate and biotransform Se, bread and durum wheat were enriched with Se through foliar and soil addition at an equivalent field rate of 100 g of Se per hectare (ha), using sodium selenate and sodium selenite as Se-supplementation matrices, in actual field conditions throughout. Biotransformation of inorganic Se was evaluated by using HPLC-ICP-MS after enzymatic hydrolysis for Se-species extraction in the resulting mature wheat grains. Selenomethionine and Se(VI) were identified and quantified: the former was the predominant species, representing 70-100 % of the total Se in samples; the maximum amount of inorganic Se was below 5 %. These results were similar for both supplementation methods and for both wheat varieties. Judging from the present results, one can conclude that agronomic biofortification of wheat may improve the nutritional quality of wheat grains with significant amounts of selenomethionine, which is an attractive option for increasing the Se status in human diets through Se-enriched, wheat-based foodstuff.

Trace-element enrichment in epiphytic lichens and tree bark at Pico Island, Azores, Portugal.

The Azores archipelago (nine islands) stretches across a sizable longitude span and sits directly on the pathway of long-range transport for airborne species over the North Atlantic Ocean. These airborne species include dusts from Africa's Sahara and Sahel and non-natural contaminants from the United States' eastern seaboard. Therefore, it is an ideal platform for watching significant deposition episodes in the area and/or simply keeping track of regular downward fluxes at ground level, either through conventional or unconventional (biological) air-monitoring approaches. For this purpose, thalli of the epiphytic lichens Parmotrema bangii (Vain.) Hale, and Parmotrema robustum (Degel) Hale; and outer bark from trunks of Cryptomeria japonica (Thunb. ex L.f.) D. Don--Japanese cedar--were collected in early 2003 at three sampling locations of Pico Island, Azores, Portugal. Lichens' phorophyte was the cedar, and local soils were sampled as well. Following suitable handling and preparation procedures, all field samples were put through instrumental neutron activation analysis (INAA; kappa O-variant) for elemental assessment. Reference data on airborne particulates were provided by a seven-wavelength aethalometer that continuously collects aerosols near the summit of Pico Mountain (observatory: 2225 m above mean sea level [AMSL]; peak: 2351 m AMSL) in quartz filter tapes. The overall results indicate that (1) the patterns of significant elemental enrichment (enrichment factor >10, relative to scandium) in lichen and bark samples are quite dissimilar, with lichen data reflecting more of the local inputs from some characteristic human activities, whereas bark appears predominantly enriched with far-ranged elements arriving in Pico's atmosphere after long-distance transport; (2) regardless of prospective elemental sources--local or global, anthropogenic or natural--bark displays a more conservative (consistent) pattern through the sampling locations; and (3) not unlike earlier indications, altitude may have a negative influence in lichen enrichment, yet the present data seem insufficient to uphold such a trend.

Copper, nickel and lead in lichen and tree bark transplants over different periods of time.

This work aimed at comparing the dynamics of atmospheric metal accumulation by the lichen Flavoparmelia caperata and bark of Platanus hybrida over different periods of time. Transplants were exposed in three Portuguese coastal cities. Samples were retrieved (1) every 2 months (discontinuous exposure), or (2) after 2-, 4-, 6-, 8- and 10-month periods (continuous exposure), and analysed for Cu, Ni and Pb. Airborne accumulation of metals was essentially independent of climatic factors. For both biomonitors [Pb]>[Ni]>[Cu] but Pb was the only element for which a consistent pattern of accumulation was observed, with the bark outperforming the lichen. The longest exposure periods hardly ever corresponded to the highest accumulation. This might have been partly because the biomonitors bound and released metals throughout the exposure, each with its own dynamics of accumulation, but both according to the environmental metal availability.

The ability of biological and organic synthetic materials to accumulate atmospheric particulates containing copper, lead, nickel and strontium.

This work was aimed at finding materials that could be used as alternatives to lichens as air quality monitors since the high natural variability and the large amount of lichen collected are two drawbacks of the use of these organisms. Lichen Flavoparmelia caperata(L.) Hale was exposed in three different forms (transplant, detached from the substratum and as a biomass-ground and homogeneized) and compared to the planetree bark (Platanus hybrida Brot.), exposed as a biomass, and two organic synthetic materials (Chelex(R) 100 resin and cellulose acetate). Materials were exposed for two months in the winter, spring and summer, at three Portuguese coastal cities. The results showed that the airborne accumulations of Cu, Ni, Pb and Sr were partially dependent on the meteorological conditions but mainly dependent on the nature of the exposed material. The standard deviations of the synthetic materials or homogenized biomass were the same or greater than lichen transplants or detached. The accumulation by biological materials, of the four studied elements, was comparable to the lichen transplant accumulation. The replacement of the traditional transplants by the biomass was not considered advantageous, since their preparation is time-consuming. Therefore lichens remain the most suitable in biomonitoring studies. The exposure of detached lichen allows the accurate measurement of the exposed area/volume so it can be useful to relate atmospheric deposition rates with the lichen metal content. The synthetic materials accumulated Cu and Ni and should only be used as an alternative to traditional transplants when these are the elements of interest.

Development and calibration of epiphytic lichens as saltfall biomonitors--dry-deposition modelling.

Lichen transplants (Ramalina calicaris and Usnea spp.) were investigated as biomonitors of the atmospheric deposition of marine salt, and a calibration model was set up to predict the dry deposition of saline elements from the concentration of salt tracers in lichens. The study was performed in the Portuguese Atlantic coast, where a monthly transplantation program was run in two stations that show clear differences in terms of precipitation regimes. At both stations, dry deposition and precipitation records were kept for the whole duration of the program. General trends in results have indicated that rainwater may wash saline elements out of lichens, though such an effect does not appear to be linear. A multiple-regression approach was taken to look for a calibration between dry-deposition fluxes and lichen concentrations through a stepwise technique. The calibration model for data obtained in both stations features two break points that define precipitation ranges for low, moderate and heavy rain conditions. The results show that lichens can really be used to indicate the dry deposition of sea salt.