The plasma membrane intactness of root-tip cells is a primary factor for Al-tolerance in cultivars of five species

We investigated the role of the cell wall and plasma membrane (PM) of root-tip cells in Al tolerance in Al-tolerant and Al-sensitive cultivars of five plant species (rice, maize, pea, wheat, and sorghum). No correlation was found between the differences in Al tolerance and the cation exchange capacity of cell walls isolated from root-tips (0–1 em). Preliminary exposure to Al for 1 h was sufficient to inhibit subsequent root re-elongation in an Al-free solution, and the inhibitory effect was more pronounced in the Al-sensitive cultivars than in the Al-tolerant ones. Together with the inhibition of root re-elongation, the PM of the root-tip cells of all the Al-sensitive cultivars was more permeabilized than that of the Al-tolerant cultivars, based on the FDA-PI fluorescence staining technique. Exposure for 30 min to Al treatment at 100 µM significantly increased the PM permeability of protoplasts isolated from the root-tips for the Al-sensitive pea cultivar placed in a moderately hypotonic medium. Protoplasts from root-tip portions of all the Al-sensitive cultivars took up more Al than those of the Al-tolerant ones when treated with 100 pM Al under isotonic conditions for 30 min. The co-existence of DNP or hypotonic conditions led to a larger increase of Al uptake by the protoplasts from Al-sensitive maize cultivars. These results suggest that Al ions rapidly alter the PM of the root-tip portion in the Al-sensitive cultivars, irrespective of plant species, resulting in an increase of the PM permeability.     

Laser-based spectroscopic methods to evaluate the humification degree of soil organic matter in whole soils: a review

Purpose

The objective of this review is to survey critically the results obtained by the application of laser-induced fluorescence spectroscopy (LIFS) and laser-induced breakdown spectroscopy (LIBS) to the evaluation of the humification degree (HD) of soil organic matter (SOM) directly in untreated, intact whole soils.

Materials and methods

A large number of soils of various origin and nature, either native or under various cultivations, land use, and management, at various depths, have been studied to evaluate the HD of their SOM directly in intact whole samples. The LIFS spectra were obtained by either a bench or a portable argon laser apparatus that emits UV-VIS light of high power, whereas the LIBS spectra were obtained using a Q-switched Nd:YAG laser at 1064 nm.

Results and discussion

The close correlations found by comparing H_LIF values of whole soil samples with values of earlier proposed humification indexes confirmed the applicability of LIFS to assess the HD of SOM in whole soils. The high correlation found between HD_LIBS values and H_LIF values showed the promising potential of LIBS for the evaluation HD of SOM.

Conclusions

The LIFS technique shows to be a valuable alternative to evaluate the HD of SOM by probing directly the whole solid soil sample, thus avoiding the use of any previous chemical and/or physical treatments or separation procedures of SOM from the mineral soil matrix. The emerging application of LIBS to evaluate the HD of SOM in whole soils appears promising and appealing due to its sensitivity, selectivity, accuracy, and precision.

     

Effect of the Nixtamalization Process on the Dietary Fiber Content,Starch Digestibility,and Antioxidant Capacity of Blue Maize Tortilla

Nixtamalization is an ancient process developed by the Mesoamerican cultures. Initially, volcanic ashes were used and then calcium hydroxide in commercial production, and more recently nixtamalization with calcium salts (NCS) has been proposed. The aim of this study was to evaluate the effect of NCS on carbohydrate digestibility and antioxidant capacity in the elaboration of blue maize tortillas. NCS in blue tortillas showed a high amount of total dietary fiber (14.27 g/100 g), the main fraction being insoluble dietary fiber. The contents of resistant starch and slowly digestible starch did not change with the nixtamalization process. The predicted glycemic index value was lower in blue tortillas with the NCS process (58) than with the traditional nixtamalization process (71). In general, NCS in blue tortillas presented a higher antioxidant capacity than traditional tortillas (ferric reducing antioxidant power method), indicating that phenolics present in blue maize maintain their activity after cooking. It can be concluded that the nutraceutical features (high dietary fiber content and antioxidant capacity) of blue maize tortillas are enhanced when they are elaborated with the NCS process.     

Heavy Metal Contamination in Sediments of Lake Nahuel Huapi,Nahuel Huapi National Park,Northern Patagonia,Argentina

Trace metals (Sb, As, Br, Cs, Co, Cr, Ag and Hg), rare earth elements (Ce, Eu, La, Lu, Sm, Tb and Yb), and Sc. were analysed in suspended load and in two sediment cores from Lake Nahuel Huapi, Nahuel Huapi National Park, Patagonia, Argentina, by using Instrumental Neutron Activation Analysis. The core activity profiles of ²¹⁰Pb and ¹³⁷Cs were measured to estimate the age of the sediments. Silver was enriched in the upper layers of both cores, and correlated with the strong growthof the population of Bariloche City in the last 50 yr. Concentrations are higher in the core sampled near Bariloche, andindicate some transport in the water body. Silver concentrationsmeasured in the suspended load were 4.58±0.36 and 3.46±0.40 μg g^-1 in the southern margin of the lake, near San Carlos de Bariloche City, whereas in the northern margin the concentrations were 1.68±0.18 and 1.88±0.23 μg g^-1. Concentration ratio for silver in suspended load and upper core layers were equal in both sampling points. These facts suggest that Ag contents correspond to inputs associated with human activities. Bromine concentrations show a strong increase abovebase line values, similar to silver. In contrast, caesium, chromium, and cobalt concentrations do not differ from base linevalues. The metalloids antimony and arsenic show little variationwith regard to base line concentration. Noticeable, the mercurycontents found in the suspended load.     

Multivariate statistical analysis of mass spectra as a tool for the classification of the main humic substances according to their structural and conformational features

The aim of this work is to explore the suitability of the complementary use of mass spectra and the corresponding statistical analysis (principal components-Pareto analysis (PCA) and discriminant analysis (DA)) of these spectra to differentiate diverse humic samples as a function of their structural and conformational features. To this end, the mass spectra of humic samples belonging to the main humic fraction types (gray humic acid, brown humic acid, and fulvic acid) were obtained by electrospray ionization mass spectrometry (ESI-MS). The results obtained showed that the application of PCA yielded a clear separation between blanks and humic samples. However, a clear differentiation among the humic fraction types was not achieved. The DA of PCA data, however, yielded a clear separation among the humic substances (HS) samples belonging to each HS fraction type considered: gray humic acids, brown humic acids, and fulvic acids. These results showed that the mass spectra of each humic sample include characteristic mass/charge (m/z) distribution values that can be considered as a "fingerprint" representative of its specific structural features. Our results also indicate that, although the m/z values principally corresponded to single-charged ions, we cannot identify these molecular weight distributions with those of humic samples, since sample molecular fragmentation, as well as partial molecular ionization, cannot be ruled out under our experimental and instrumental conditions.     

Assessing insecticide and fungicide effects on the culturable soil bacterial community by analyses of variance of their DGGE fingerprinting data

To assess the effects of three insecticides (aldicarb, chlorpyrifos, deltamethrin) and two fungicides (tebuconazole and metalaxyl + mancozeb) on the PCR-DGGE fingerprints of culturable soil bacterial communities (CSBC), a greenhouse experiment was carried out with soil samples from an Integrated System for Agroecological Production (ISAP), a Conventional Potato Production Area (CPPA) and a Secondary Forest Area (SFA) close to the CPPA. Samples were obtained at 15 day intervals starting at 32 until 77 days after sowing (DAS) to perform the PCR-DGGE analysis of the CSBC cultured on media amended with soil suspension. Analysis of variance from PCR-DGGE data indicated significant differences among treatments. Regardless the type of pesticide applied, CSBC was disturbed and similarity values varied from 5% to 90% in comparison to the control. Significant shifts on CSBC were only detected among treatments in the first two harvests, while CSBC tended to be more akin to each other at the last two harvest dates. The most significant responses observed were due to different soil sample origins, where values of 5% of similarity to the control were observed on CPPA soil. The use of analysis of variance on PCR-DGGE data was useful to a better understanding of the changes on CSBC induced by pesticides applications.     

Copper Biosorption by Biomass of Marine Alga: Study of Equilibrium and Kinetics in Batch System and Adsorption/Desorption Cycles in Fixed Bed Column

Copper biosorption onto chemically modified biomass of marine alga Sargassum filipendula was investigated in a batch reactor and a fixed bed column. Experiments were carried out in the batch reactor to obtain kinetic and equilibrium data and to assess the copper desorption efficiency of different eluent solutions. The pseudo-first-order, pseudo-second-order, and Langmuir kinetic models were used to correlate kinetic data. The experimental data fitted well to the pseudo first order and Langmuir kinetic models. Langmuir and Freundlich models were applied to describe the equilibrium data obtained at a fixed temperature of 30°C and at pH values of 3.0, 4.0, 5.0, and 6.0. The maximum capacities of copper biosorption onto the algal biomass were 1.43, 1.59, 2.40, and 2.36 mequiv./g at pH 3.0, 4.0, 5.0, and 6.0, respectively. The efficiencies of two eluent solutions (calcium chloride and hydrochloric acid) for copper removal from the biomass were evaluated at different concentrations (0.1, 0.2, 0.5, and 1.0 mol/L). The efficiencies of the calcium chloride solutions varied from 1% to 14%, while efficiencies varying from 95% to 99% were obtained when hydrochloric acid solutions were applied. Three adsorption/desorption cycles were carried out in a fixed bed column using 0.1 mol/L hydrochloric acid as eluent solution. The results showed that an increase in the number of cycles led to a reduction in the adsorption capacity of the alga. The desorbed copper fraction presented no significant variation, remaining around 63% in the three adsorption/desorption cycles.     

Allergenicity assessment of the papaya ringspot virus coat protein expressed in transgenic rainbow papaya

The virus-resistant, transgenic commercial papaya Rainbow and SunUp (Carica papaya L.) have been consumed locally in Hawaii and elsewhere in the mainland United States and Canada since their release to planters in Hawaii in 1998. These papaya are derived from transgenic papaya line 55-1 and carry the coat protein (CP) gene of papaya ringspot virus (PRSV). The PRSV CP was evaluated for potential allergenicity, an important component in assessing the safety of food derived from transgenic plants. The transgene PRSV CP sequence of Rainbow papaya did not exhibit greater than 35% amino acid sequence homology to known allergens, nor did it have a stretch of eight amino acids found in known allergens which are known common bioinformatic methods used for assessing similarity to allergen proteins. PRSV CP was also tested for stability in simulated gastric fluid and simulated intestinal fluid and under various heat treatments. The results showed that PRSV CP was degraded under conditions for which allergenic proteins relative to nonallergens are purported to be stable. The potential human intake of transgene-derived PRSV CP was assessed by measuring CP levels in Rainbow and SunUp along with estimating the fruit consumption rates and was compared to potential intake estimates of PRSV CP from naturally infected nontransgenic papaya. Following accepted allergenicity assessment criteria, our results show that the transgene-derived PRSV CP does not pose a risk of food allergy.     

Precipitation chemistry in Japan 1989–1993

Precipitation chemistry in Japan was discussed on a wet-only sample database obtained in a nationwide survey from April 1989 to March 1993. Wet-only samples were collected at 29 stations over Japan on a biweekly basis. Commonly determined chemical parameters were measured in laboratories. The volume-weighted annual mean pH at each site ranged from 4.50 to 5.83 with a mean of 4.76. Concentration ranges and means (parenthesized) on an equivalent basis for major ions were as follows: nss-SO₄ ^2–; 5.2–58.9 (38.6), NO₃ ^–; 1.8–25.0 (14.1), NH₄ ⁺; 0.55–29.8 (18.3), nss-Ca²⁺; 2.0–34.5(14.2), Na⁺; 6.4–275.3 (49.1), Cl^–; 13.7–322.4 (63.5) eq L^–1. Acid-base relationships for Phase-II records were quantitatively discussed in terms of three measures: pH, fractional acidity, and our proposed pA_i.