Ozone pollution influences soil carbon and nitrogen sequestration and aggregate composition in paddy soils

Background and aims

Much attention has focused on the effects of tropospheric ozone (O₃) on terrestrial ecosystems and plant growth. Since O₃ pollution is currently an issue in China and many parts of the world, understanding the effects of elevated O₃ on soil carbon (C) and nitrogen (N) sequestration is essential for efforts to predict C and N cycles in terrestrial ecosystems under predicted increases in O₃. Thus the main objective of this study was to determine whether an increases in atmospheric O₃ concentration influenced soil organic C (SOC) and N sequestration.

Methods

A free-air O₃ enrichment (O₃-FACE) experiment was started in 2007 and used continuous O₃ exposure from March to November each year during crop growth stage in a rice (Oryza sativa L.)—wheat (Triticum aestivum L.) rotation field in the Jiangsu Province, China. We investigated differences in SOC and N and soil aggregate composition in both elevated and ambient O₃ conditions.

Results

Elevated atmospheric O₃ (18–80 nmol mol^?1 or 50 % above the ambient) decreased the SOC and N concentration in the 0–20 cm soil layer after 5 years. Elevated O₃ significantly decreased the SOC concentration by 17 % and 5.6 % in the 0–3 cm and the 10–20 cm layers, respectively. Elevated O₃ significantly decreased the N concentration by 8.2–27.8 % in three layers at the 20 cm depth. In addition, elevated O₃ influenced the formation and transformation of soil aggregates and the distribution of SOC and N in the aggregates across soil layer classes. Elevated O₃ significantly decreased the macro-sized aggregate fraction (16.8 %) and associated C and N (0.5 g kg^?1 and 0.32 g kg^?1, respectively), and significantly increased the silt+ clay-sized aggregate fraction (61 %) and associated C (1.7 g kg^?1) in the 0–3 cm layer. Elevated O₃ significantly decreased the macro-sized aggregate fraction (9.6 %) and associated C and N (1.4 g kg^?1 and 0.35 g kg^?1, respectively), and significantly increased the silt+ clay-sized aggregate fraction (41.8 %) and decreased the corresponding associated N (0.14 g kg^?1) in the 3–10 cm layer. Elevated O₃ did not significantly effect the formation and transformation of aggregates in the 10–20 cm layer, yet it did significantly increase the C concentration in the macro-sized fraction (1 g kg^?1) and decrease the N concentration in the macro- and micro-sized fractions (0.24 g kg^?1 and 0.16 g kg^?1, respectively).

Conclusion

Long-term exposure to elevated atmospheric O₃ negatively affected the physical structure of the soil and impaired soil C and N sequestration.     

Mycotoxigenic fungi and mycotoxins associated with stored maize from different regions of Lesotho

Samples of stored maize from villages located in five different agroecological zones (southern lowlands, northern lowlands, Senqu river valley, foothills and mountains) of Lesotho were collected in 2009/10 and 2010/11 and assessed for contamination with toxigenic fungi. The water activity of all samples collected during the two seasons was <0.70. The total fungal populations of the maize from different regions in the two seasons was not significantly different (p?>?0.05). Fusarium verticillioides, F. proliferatum and F. subglutinans predominated in different regions in both seasons based on molecular analyses. In the 2009/10 season, the isolates of these species all produced FB₁, while in the 2010/11 season, very few produced FB₁. A. flavus isolates (2009/10) were recovered from mountains and Senqu river valley samples while the 2010/11 isolates were predominantly from the foothills and northern lowlands. The mountain isolates of Aspergillus section Flavi produced the highest levels of AFB₁ (20 mg kg^?1). Aspergillus parasiticus was only isolated from the foothills, Senqu river valley and southern lowlands samples, and the AFB₁ levels produced ranged from ‘none detected’ to 3.5 mg kg^?1. The Aspergillus ochraceous isolates were least frequently encountered in both seasons. In the 2009/10 season, the isolates from the northern lowlands produced ochratoxin A (OTA) in culture. No isolates of A. niger from different regions in both seasons produced any OTA. Multi-mycotoxin analyses of the maize samples were done for a range of mycotoxins. At least one sample from each region in both seasons was FB₁-positive. FB₁ levels for 2010/11 samples (7–936 μg kg^?1) were higher than in the 2009/10 season (2–3 μg kg^?1). In both seasons, the mountains registered the highest levels of FB₁. Deoxynivalenol (DON) was recovered from all the samples analysed, with the highest mean contamination of 1,469 μg kg^?1 in samples from the northern lowlands. Moniliformin (MON) was detected from all agroecological zones in the two seasons (5–320 μg kg^?1 in 2009/10; 15–1,205 μg kg^?1 in 2010/11). Emerging toxins such as fusaproliferin (FUS) and beauvericin (BEA) were also detected. OTA was not detected in any of the samples analysed. Only one 2009/10 sample in the Senqu river valley was positive for AFB₁. This is the first report on toxigenic fungi and multi-mycotoxin contamination of maize samples from subsistence farmers’ stores in different agroecological zones of Lesotho.     

Comparison of two protocols for field immobilization of white-eared opossums (<Emphasis Type="Italic">Didelphis albiventris</Emphasis>)

The aim of this study was to investigate the efficacy of two protocols for field immobilization of white-eared opossums (Didelphis albiventris) and compare their effects on immobilization, cardiopulmonary variables, and recovery times. Twenty one opossums were randomly divided into two groups; G1 received ketamine (15 mg kg^?1)-dexmedetomidine (0.15 mg kg^?1) intramuscularly (IM) and G2 received the ketamine-dexmedetomidine combination and isoflurane once induction was achieved. Oxygen was delivered by face mask (1.5 L minute^?1). Thirty minutes after induction, isoflurane was discontinued (G2) and both groups were administered atipamezole (1.5 mg kg^?1) IM. Respiratory (?_R) and heart rate (HR), oxyhemoglobin saturation (SpO₂), and rectal temperature (T) were recorded every 5 min. Induction time, time to first movement (RT₁), and time to achieve standing (RT₂) were recorded. ANOVA and non-parametric tests were used. Level of immobilization was assessed by observation of movements and evaluation of muscle relaxation. The mean induction time was 4.71 min. RT₁ and RT₂ were significantly longer in G2. No significant differences were found in SpO₂ or ?R. HR did not vary significantly along time, but was higher in G2. Rectal temperature did not show differences between treatments, but decreased significantly with time in G2. Four of nine animals in G1 showed movements, while no animals in G2 did and muscle relaxation was determined to be better in this latter group. Both protocols were adequate for short-term field immobilization, with minimal alterations of HR and T and relatively short recovery times. Isoflurane provided better immobilization with statistically significant prolongation of recovery times.     

Zinc seed coating improves the growth,grain yield and grain biofortification of bread wheat

This study, comprising three independent experiments, was conducted to optimize the zinc (Zn) application through seed coating for improving the productivity and grain biofortification of wheat. Experiment 1 was conducted in petri plates, while experiment 2 was conducted in sand-filled pots to optimize the Zn seed coating using two sources (ZnSO₄, ZnCl₂) of Zn. In the first two experiments, seeds of two wheat cultivars Lasani-2008 and Faisalabad-2008 were coated with 0.25, 0.50, 0.75, 1.00, 1.25, 1.50, 1.75 and 2.00 g Zn kg^?1 seed using ZnSO₄ and ZnCl₂ as Zn sources. The results of experiment I revealed that seed coating with 1.25 and 1.50 g Zn kg^?1 seed using both sources of Zn improved the seedling emergence. However, seed coated with 1.25 and 1.50 g Zn kg^?1 seed using ZnSO₄ was better regarding improvement in seedling growth and seedling dry weight. The results of the second experiment indicated that seed coated with 1.25 and 1.50 g Zn kg^?1 seed using ZnSO₄ improved the seedling emergence and seedling growth of tested wheat cultivars. However, seed coating beyond 1.5 g Zn kg^?1 seed using either Zn source suppressed the seedling emergence. Third experiment was carried out in glass house in soil-filled earthen pots. Seeds of both wheat cultivars were coated with pre-optimized treatments (1.25, 1.50 g Zn kg^?1 seed) using both Zn sources. Seed coating with all treatments of ZnSO₄ and seed coating with 1.25 g Zn kg^?1 seed using ZnCl₂ improved the seedling emergence and yield-related traits of wheat cultivars. Seed coating with 1.25 g Zn kg^?1 seed also improved the chlorophyll a and b contents. Maximum straw Zn contents, before and after anthesis, were recorded from seed coated with 1.5 g Zn kg^?1 seed using either Zn source. Increase in grain yield from seed coating followed the sequence 1.25 g Zn kg^?1 seed (ZnSO₄) >1.25 g Zn kg^?1 seed (ZnCl₂) >1.5 g Zn kg^?1 seed (ZnSO₄). However, increase in grain Zn contents from seed coated was 1.5 g Zn kg^?1 seed (ZnCl₂) >1.25 and 1.5 g Zn kg^?1 seed (ZnCl₂, ZnSO₄) >1.25 g Zn kg^?1 seed (ZnSO₄). Seed coating with Zn increased the grain Zn contents from 21 to 35 %, while 33–55 % improvement in grain yield was recorded. In conclusion, wheat seeds may be coated with 1.25 g Zn kg^?1 seed using either source of Zn for improving the grain yield and grain Zn biofortification.     

Physiological and Biochemical Mechanisms Preventing Cd Toxicity in the New Hyperaccumulator <Emphasis Type="Italic">Abelmoschus manihot</Emphasis>

Abelmoschus manihot, an ornamental plant, was examined for phytoremediation purposes in accordance with the ability to accumulate cadmium and physiological mechanisms of cadmium tolerance. A net photosynthetic rate (A _N) glasshouse experiment for 60 days was conducted to investigate the influence of different cadmium amounts (0–100 mg kg^?1) on the growth, biomass, photosynthetic performance, reactive oxygen species (ROS) production, antioxidative enzyme activities, Cd uptake and accumulation of A. manihot. Exposure to cadmium enhanced plant growth even at 100 mg kg^?1, without showing symptoms of visible damage. The cadmium concentration of shoots (stems or leaves) and roots was more than the critical value of 100 mg kg^?1 and reached 126.17, 185.26 and 210.24 mg kg^?1, respectively. BCF values of A. manihot plants exceeded the reference value 1.0 for all the Cd treatments, and TF values were greater than 1 at 15–60 mg kg^?1 Cd treatment. The results also showed that cadmium concentrations of 60 mg kg^?1 or less induced a significant enhancement in plant net photosynthetic rate (A _N), stomatal conductance (G _s), transpiration rate (T _r), photosynthetic pigments and F _v/F _m. These parameters were slightly decreased at the higher concentration (100 mg kg^?1). The ROS production (O₂ ^?, H₂O₂) and antioxidative response including SOD, CAT and POD were significantly enhanced by increasing cadmium. These results suggest that A. manihot can be considered as a Cd-hyperaccumulator and the hormetic effects may be taken into consideration in remediation of Cd contamination soil.     

Changes in bacterial CO2 fixation with depth in agricultural soils

Soils were incubated continuously in an atmosphere of ¹⁴CO₂ and the distribution of labeled C into soil organic carbon (¹⁴C-SOC) was determined at 0–1, 1–5, and 5–17 cm down the profile. Significant amounts of ¹⁴C-SOC were measured in paddy soils with a mean of 1,180.6?±?105.2 mg kg^–1 at 0–1 cm and 135.3?±?47.1 mg kg^?1 at 1–5 cm. This accounted for 5.9?±?0.7 % and 0.7?±?0.2 %, respectively, of the total soil organic carbon at these depths. In the upland soils, the mean ¹⁴C-SOC concentrations were 43 times (0–1 cm) and 11 times (1–5 cm) lower, respectively, than those in the paddy soils. The amounts of ¹⁴C incorporated into the microbial biomass (MBC) were also much lower in upland soils (5.0?±?3.6 % and 2.9?±?1.9 % at 0–1 and 1–5 cm, respectively) than in paddy soils (34.1?±?12.4 % and 10.2?±?2.1 % at 0–1 and 1–5 cm, respectively). Similarly, the amount of ¹⁴C incorporated into the dissolved organic carbon (DOC) was considerably higher in paddy soils (26.1?±?6.9 % and 6.9?±?1.3 % at 0–1 and 1–5 cm, respectively) than in upland soils (6.0?±?2.7 % and 4.3?±?2.2 %, respectively). The observation that the majority of the fixed ¹⁴C-SOC, RubisCO activity and cbbL gene abundance were concentrated at 0–1 cm depth and the fact that light is restricted to the top few millimeters of the soil profiles highlighted the importance of phototrophs in CO₂ fixation in surface soils. Phylogenetic analysis of the cbbL genes showed that the potential for CO₂ fixation was evident throughout the profile and distributed between both photoautotrophic and chemoautotrophic bacteria such as Rhodopseudomonas palustris, Bradyrhizobium japonicum, Rubrivivax gelatinosus and Ralstonia eutropha.     

Toxicity of an Annonin-Based Commercial Bioinsecticide Against Three Primary Pest Species of Stored Products

The effects of a bioinsecticide formulation based on extract of Annona squamosa L. (Annonaceae) containing 10,000 mg L^?1 of acetogenin annonin as the main active ingredient were investigated against three primary pest species of stored grains in Brazil [maize weevil Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), Mexican bean weevil Zabrotes subfasciatus (Boheman) (Coleoptera: Chrysomelidae: Bruchinae), and cowpea weevil Callosobruchus maculatus (Fabricius) (Coleoptera: Chrysomelidae: Bruchinae)] by means of residual contact bioassays. In a concentration-dependent manner, the annonin-based commercial bioinsecticide caused significant adult mortality of C. maculatus (LC₅₀ = 6890 μL kg^?1), S. zeamais (LC₅₀ = 2781 μL kg^?1), and Z. subfasciatus (LC₅₀ = 2120 μL kg^?1) after 120 h of residual contact exposure. In addition to acute toxicity, the tested bioinsecticide also promoted a significant reduction of the number of eggs laid by females of C. maculatus (EC₅₀ = 5949.7 μL kg^?1) and Z. subfasciatus (EC₅₀ = 552.7 μL kg^?1). Moreover, the bioinsecticide significantly reduced the number of emerged insects (F₁ generation) of C. maculatus (EC₅₀ = 2763.0 μL kg^?1), S. zeamais (EC₅₀ = 1380.8 μL kg^?1), and Z. subfasciatus (EC₅₀ = 561.5 μL kg^?1). The bioinsecticide also reduced the percentage of damaged grains for the three pest species studied, and its grain-protectant properties are comparable to or superior in efficacy in relation to a diatomaceous earth-based insecticide (Insecto® at 1000 mg kg^?1) used as a positive control. Thus, this standardized formulation has promising bioactivity against stored insect species and can be a useful component for IPM of stored grains in Brazil and elsewhere.     

Co-occurrence of five Fusarium toxins in corn-Dried Distiller’s Grains with Solubles in Thailand and comparison of ELISA and LC-MS/MS for fumonisin analysis

Dried Distiller’s Grains with Solubles (DDGS), a by-product of bio-ethanol production from maize and other cereals, is increasingly used as a feed additive. In this study, five Fusarium toxins, including fumonisin B₁ (FB₁), fumonisin B₂ (FB₂), deoxynivalenol (DON), zearalenone (ZEN) and beauvericin (BEA) were quantified by LC-MS/MS in 59 corn-DDGS samples. In addition, the fumonisin level in 30 randomly selected-samples was compared using an ELISA detection technique. No sample was free from mycotoxin contamination, and 50.8 % of the samples were co-contaminated with all five mycotoxins. Moreover, toxin levels were generally high, with mean levels of 9 mg kg^?1 FB₁, 6 mg kg^?1 FB₂, 1.2 mg kg^?1 DON, 0.9 mg kg^?1 ZEN, and 0.35 mg kg^?1 BEA. Maximum levels for FB₁ (143 mg kg^?1) and FB₂ (125 mg kg^?1) are of acute toxicological relevance. The ELISA method had a tendency to underestimate the fumonisin content when compared with LC-MS/MS. Finally, this is the first reported beauvericin contamination in corn-DDGS.     

Distribution of Metals (Cu,Zn, Pb,and Cd) in Sediments of the Anzali Lagoon,North Iran

Concentrations of four metals (Cu, Zn, Pb, and Cd) in the sediments of the Anzali Lagoon in the northern part of Iran were determined to evaluate the level of contamination and spatial distribution. The sediments were collected from 21 locations in the lagoon. At each lagoon site a core, 60 cm long, was taken. The ranges of the measured concentrations in the sediments are as follows: 17–140 mg kg^?1 for Cu, 20–113 mg kg^?1 for Zn, 1–37 mg kg^?1 for Pb and 0.1–3.5 mg kg^?1 for Cd in surficial (0-20 cm) and 16–87 mg kg^?1 for Cu, 28.5–118 mg kg^?1 for Zn, 3–20 mg kg^?1 for Pb and 0.1–3.5 mg kg^?1 for Cd in deep (40–60 cm) sediments. The results of the geoaccumulation index (I_geo) show that Cd causes moderate to heavy pollution in most of the study area. Environmental risk evaluation showed that the pollution in the Anzali Lagoon is moderate to considerable and the ranking of the contaminants followed the order: Cd > Cu > Pb > Zn. Some locations present severe pollution by metals depending on the sources, of which sewage outlets and phosphate fertilizers are the main sources of contaminants to the area.     

Concentrations and Health Risk of Polycyclic Aromatic Hydrocarbons in Some Brands of Biscuits in the Nigerian Market

Concentrations of 16 priority polycyclic aromatic hydrocarbons (PAHs) were determined in 40 brands of biscuits in the Nigerian market. The analyses were performed by gas chromatography-flame ionisation detection (GC-FID) after Soxhlet extraction of the sample with hexane/dichloromethane and clean-up of the extract. The concentrations of Σ16 PAHs in these biscuit samples were in the range of 35.7–645.3 μg kg^?1, 75.9–490.7 μg kg^?1, 91.5–537 μg kg^?1, 18.4–522.2 μg kg^?1, 123.5–393.8 μg kg^?1, 167.2–880 μg kg^?1, 136.5–316 μg kg^?1, and 135.5–241.6 μg kg^?1 for shortcake, digestives, cookies, shortbread, wafers, crackers, Pringles, and cabin, respectively. The concentrations of Σ8 carcinogenic PAHs in the samples ranged from not detected (nd)–323.3 μg kg^?1, 15.7–138 μg kg^?1, 9.7–312.9 μg kg^?1, nd–331.7 μg kg^?1, nd–220.9 μg kg^?1, nd–53.3 μg kg^?1, 18.4–56.6 μg kg^?1, and 6.6–170.8 μg kg^?1 for shortcake, digestives, cookies, shortbread, wafers, crackers, Pringles, and cabin, respectively. The margin of exposure (MOE), based on PAH8 as an indicator for the occurrence and effects of PAHs in food, was less than 10,000, the serious health effects value, in 30% and 8% of the brands for the child and adult scenarios, respectively.     

Dietary Supplementation of Zinc Nanoparticles and Its Influence on Biology,Physiology and Immune Responses of the Freshwater Prawn,Macrobrachium rosenbergii

The present study was conducted to assess the influence of dietary zinc nanoparticles (size 50 nm) on the growth, biochemical constituents, enzymatic antioxidant levels and the nonspecific immune response of the freshwater prawn, Macrobrachium rosenbergii post larvae (PL). The concentrations of dietary supplement zinc nanoparticles (ZnNPs) were 0, 10, 20, 40, 60 and 80 mg kg^?1 with the basal diet, and the level of Zn in ZnNP-supplemented diets were 0.71, 10.61, 20.73, 40.73, 60.61 and 80.60 mg kg^?1, respectively. ZnNP-incorporated diets were fed to M. rosenbergii PL (initial body weight, 0.18?±?0.02 g) in a triplicate experimental setup for a period of 90 days. ZnNP supplemented feed fed PL up to 60 mg kg^?1 showed significantly (P?<?0.05) improved performance in survival, growth and activities of digestive enzymes (protease, amylase and lipase). The concentrations of biochemical constituents (total protein, total amino acid, total carbohydrate and total lipid), total haemocyte count and differential haemocyte count were elevated in 10–60 mg kg^?1 ZnNP supplemented feed fed PL. However, the PL fed with 80 mg ZnNPs kg^?1 showed negative results. Activities of enzymatic antioxidants [superoxide dismutase (SOD) and catalase (CAT)], metabolic enzymes [glutamate–oxaloacetate transaminase (GOT) and glutamate–pyruvate transaminase (GPT)] and the process of lipid peroxidation (LPO) in the hepatopancreas and muscle showed no significant alterations in 10–60 mg kg^?1 ZnNP supplemented feed fed PL. Whereas, 80 mg ZnNPs kg^?1 supplemented feed fed PL showed significant elevations in SOD, CAT, LPO, GOT and GPT. Therefore, 80 mg ZnNPs kg^?1 was found to be toxic to M. rosenbergii PL. Thus, the study suggests that up to 60 mg ZnNPs kg^?1 can be supplemented for regulating survival, growth and immunity of M. rosenbergii.     

Heavy Metals Bioconcentration from Soil to Vegetables and Assessment of Health Risk Caused by Their Ingestion

The present study was undertaken to assess the non-carcinogenic human health risk of heavy metals through the ingestion of locally grown and commonly used vegetables viz. Raphanus sativus (root vegetable), Daucus carota (root vegetable), Benincasa hispida (fruit vegetable) and Brassica campestris leaves (leafy vegetable) in a semi-urbanized area of Haryana state, India. Heavy metal quantification of soil and vegetable samples was done using flame atomic absorption spectrophotometer. Lead, cadmium and nickel concentration in vegetable samples varied in range of 0.12–6.54 mg kg^?1, 0.02–0.67 mg kg^?1 and <0.05–0.41 mg kg^?1, respectively. Cadmium and lead concentration in some vegetable samples exceeded maximum permissible limit given by World Health Organization/Food and Agriculture Organization and Indian standards. Much higher concentrations of Pb (40–190.5 mg kg^?1), Cd (0.56–9.85 mg kg^-1) and Ni (3.21–45.87 mg kg^?1) were reported in corresponding vegetable fields’ soils. Correlation analysis revealed the formation of three primary clusters, i.e. Cu–Cd, Cd–Pb and Ni–Zn in vegetable fields’ soils further supported by cluster analysis and principal component analysis. Bioconcentration factor revealed that heavy metals’ uptake was more by leafy vegetable than root and fruit vegetables. Hazard index of all the vegetables was less than unity; thus, the ingestion of these vegetables is unlikely to pose health risks to the target population.     

Interactive effects of molybdenum and phosphorus fertilizers on photosynthetic characteristics of seedlings and grain yield of Brassica napus

A pot experiment with acid yellow–brown soil was conducted to investigate the interactive effects of molybdenum (Mo) and phosphorus (P) fertilizers on the photosynthetic characteristics of seedlings and grain yield of Brassica napus which is sensitive to soil P and Mo deficiency. Both Mo and P fertilizers were applied at three levels (0 mg Mo kg^?1, 0.15 mg Mo kg^?1, 0.30 mg Mo kg^?1 soil; 0 mg P kg^?1, 80 mg P kg^?1, 160 mg P kg^?1 soil). The results showed that P fertilizer application increased grain yield, soluble sugar concentrations of seedling leaves, DM and P accumulation of seedling shoots of Brassica napus in the absence or presence of Mo fertilizer. In contrast, Mo fertilizer increased these parameters only in the presence of P fertilizer. Mo accumulation in shoots, chlorophyll concentrations and net photosynthesis rate (P _n) of seedling leaves were increased by both Mo and P fertilizers, particularly with the combination of the two fertilizers. The results also showed that the Mo and P fertilizers increased photosynthetic rate through two different mechanisms, with Mo increasing photosynthetic activity of mesophyll cells, and P increasing stomatal conductance. The results demonstrate that there was a synergetic effect on photosynthesis and grain yield between Mo and P fertilizers and it is conducive for Brassica napus growth to co-apply the two fertilizers.     

Does radial oxygen loss and iron plaque formation on roots alter Cd and Pb uptake and distribution in rice plant tissues?

Background and Aims

Metal (e.g. Cd and Pb) pollution in agricultural soils and crops have aroused considerable attention in recent years. This study aimed to evaluate the effects of ROL and Fe plaque on Cd and Pb accumulation and distribution in the rice plant.

Methods

A rhizobag experiment was employed to investigate the correlations among radial oxygen loss (ROL), Fe plaque formation and uptake and distribution of Cd and Pb in 25 rice cultivars.

Results

Large differences between the cultivars were found in rates of ROL (1.55 to 6.88 mmol O₂ kg^?1 root d.w. h^?1), Fe plaque formation (Fe: 6,117–48,167 mg kg^?1; Mn: 127–1,089 mg kg^?1), heavy metals in shoot (Cd: 0.13–0.35 mg kg^?1; Pb: 4.8–8.1 mg kg^?1) and root tissues (Cd: 1.1–3.5 mg kg^?1; Pb: 45–199 mg kg^?1), and in Fe plaque (Cd: 0.54–2.6 mg kg^?1; Pb: 102–708 mg kg^?1). Rates of ROL were positively correlated with Fe plaque formation and metal deposition on root surfaces, but negatively correlated with metal transfer factors of root/plaque and distributions in shoot and root tissues.

Conclusions

ROL-induced Fe plaque promotes metal deposition on to root surfaces, leading to a limitation of Cd and Pb transfer and distribution in rice plant tissues.     

Hepatosplenomegaly and phytotoxicity of a planktonic cyanobacterium Nostoc sp. BHU001 isolated from agricultural pond

Nostoc sp. BHU001, a planktonic cyanobacterium isolated from an agricultural pond in India, was examined for its toxicity. Mice, administered intraperitoneally with Nostoc sp. BHU001 crude extract (50 mg kg^?1 body weight) died at 4.5 h. Examination of liver and spleen showed microcystin (MC)-like symptoms. Serum enzyme aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities increased by 1.6–1.8 and 2.6–3.0-folds, respectively at 50 and 100 mg crude extract kg^?1 body weight. Thin layer chromatography of the crude extract produced five bands (N-1 to N-5). UV absorption maxima of band N-4 corresponded to that of standard microcystin-LR. Further analysis of the band N-4 by high-performance liquid chromatography gave a retention time (R _t ) of 4.61 min similar to that of standard microcystin–LR (LR stands for lysine and arginine). Total MC content was quantified by enzyme-linked immunosorbent assay, and was 189.9 μg g^?1 of crude extract, 9.8 μg l^?1 of spent medium and 5.5 μg l^?1 of pond water. Exposure of rice (Oryza sativa var. Sonam) seeds to the crude extract did not affect their germination, but inhibited the root and shoot growth of seedlings by 27.3 and 42.89 folds at 3 mg ml^?1 crude extract, respectively.     

Screening survey of co-production of fusaric acid,fusarin C,and fumonisins B1, B2 and B3 by Fusarium strains grown in maize grains

Fusarium species isolated from Belgian maize were screened for their ability to produce fusarin C, fusaric acid, fumonisins B₁ (FB₁), FB₂ and FB₃ in maize grains. First, cultivation of Fusarium species in Myro liquid medium allowed overcoming the shortage of the standard of fusarin C on the market. All Fusarium verticillioides produced much higher contents of mycotoxins in Myro compared to Fusarium graminearum or Fusarium venenatum. The optimization of the LC-MS/MS method resulted in low limits of detection and quantification for fusarin C, fusaric acid, FB₁, FB₂ and FB₃ determination in maize grains. Its application for screening the potential toxin production ability evidenced that the concentrations of the analytes were significantly increased at various levels when F. verticillioides strains were cultivated in maize grains and reached 441 mg kg^?1 for fusaric acid, 74 mg kg^?1 for fusarin C, 1,301 mg kg^?1 for FB₁, 367 mg kg^?1 for FB₂ and 753 mg kg^?1 for FB₃.     

High tolerance of aluminum in the grass species Cynodon aethiopicus

Concentrations of aluminum (Al) were determined in leaves of native terrestrial plants, macrophytes and fruit parts (watermelon and tomato) using inductively coupled plasma mass spectrometry. Al concentrations in water and soil were determined by inductively coupled plasma optical emission spectrometry. Potamogeton thunbergii (macrophyte) and Cynodon aethiopicus (terrestrial grass) had the highest leaf Al concentrations (2 and 1 g kg^?1 dw, respectively). Transfer factors (mg kg^?1 dw plants/mg kg^?1 dw soil) based on total Al concentrations in soil varied from 2 × 10^?3 to 0.05 and from 1.9 to 78 based on mobile Al concentrations determined after sequential extraction. Bioconcentration factors (mg kg^?1 dw plants/mg L^?1 water) varied from 19 to 9.5 × 10³ L kg^?1 dw. Plants can accumulate high concentrations of Al when growing in neutral pH soils and slightly alkaline lakes in the Ethiopian Rift Valley. Controlled experiments showed that C. aethiopicus can accumulate high levels of Al both in root and shoot. Compared to Arabidopsis thaliana, C. aethiopicus was more tolerant to Al exposure as ≥400 μM AlCl₃ was needed to inhibit root growth compared to 200 μM in A. thaliana. After exposing C. aethiopicus and A. thaliana in 800 μM AlCl_3, alkaline comet assay indicates significant DNA (deoxyribonucleic acid) damage in A. thaliana while C. aethiopicus was unaffected. No significant induction of reactive oxygen species (ROS), in terms of leaf H₂O₂ levels, could be observed in C. aethiopicus. C. aethiopicus has mechanisms to suppress both Al-induced ROS and DNA damage, thereby increasing tolerance of the species to high Al concentrations.     

Soil N and C trace gas fluxes and microbial soil N turnover in a sessile oak (Quercus petraea (Matt.) Liebl.) forest in Hungary

During two intensive field campaigns in summer and autumn 2004 nitrogen (N₂O, NO/NO₂) and carbon (CO₂, CH₄) trace gas exchange between soil and the atmosphere was measured in a sessile oak (Quercus petraea (Matt.) Liebl.) forest in Hungary. The climate can be described as continental temperate. Fluxes were measured with a fully automatic measuring system allowing for high temporal resolution. Mean N₂O emission rates were 1.5 μg N m⁻² h⁻¹ in summer and 3.4 μg N m⁻² h⁻¹ in autumn, respectively. Also mean NO emission rates were higher in autumn (8.4 μg N m⁻² h⁻¹) as compared to summer (6.0 μg N m⁻² h⁻¹). However, as NO₂ deposition rates continuously exceeded NO emission rates (−9.7 μg N m⁻² h⁻¹ in summer and −18.3 μg N m⁻² h⁻¹ in autumn), the forest soil always acted as a net NO _x sink. The mean value of CO₂ fluxes showed only little seasonal differences between summer (81.1 mg C m⁻² h⁻¹) and autumn (74.2 mg C m⁻² h⁻¹) measurements, likewise CH₄uptake (summer: −52.6 μg C m⁻² h⁻¹; autumn: −56.5 μg C m⁻² h⁻¹). In addition, the microbial soil processes net/gross N mineralization, net/gross nitrification and heterotrophic soil respiration as well as inorganic soil nitrogen concentrations and N₂O/CH₄ soil air concentrations in different soil depths were determined. The respiratory quotient (ΔCO_{2 resp} ΔO_{2 resp}⁻¹) for the uppermost mineral soil, which is needed for the calculation of gross nitrification via the Barometric Process Separation (BaPS) technique, was 0.8978 ± 0.008. The mean value of gross nitrification rates showed only little seasonal differences between summer (0.99 μg N kg⁻¹ SDW d⁻¹) and autumn measurements (0.89 μg N kg⁻¹ SDW d⁻¹). Gross rates of N mineralization were highest in the organic layer (20.1–137.9 μg N kg⁻¹ SDW d⁻¹) and significantly lower in the uppermost mineral layer (1.3–2.9 μg N kg⁻¹ SDW d⁻¹). Only for the organic layer seasonality in gross N mineralization rates could be demonstrated, with highest mean values in autumn, most likely caused by fresh litter decomposition. Gross mineralization rates of the organic layer were positively correlated with N₂O emissions and negatively correlated with CH₄ uptake, whereas soil CO₂ emissions were positively correlated with heterotrophic respiration in the uppermost mineral soil layer. The most important abiotic factor influencing C and N trace gas fluxes was soil moisture, while the influence of soil temperature on trace gas exchange rates was high only in autumn.     

Sulfur and molybdenum fractionation in marine and riverine alluvium paddy soils

Intermittently submergence and drainage status of paddy fields can cause alterations in morphological and chemical characteristics of soils. We conducted a sequential fractionation study to provide an insight into solubility of Sulfur (S) and Molybdenum (Mo) in flooded alluvial paddy soils. The samples (0–15 and 15–30 cm) were taken from marine and riverine alluvial soils in Kedah and Kelantan areas, respectively, and were sequentially extracted with NaHCO₃, NaOH, HCl, and HClO₄–HNO₃. Total S in upper and lower layers of Kedah and Kelantan ranged between 273 and 1121 mg kg^?1, and 177 to 1509 mg kg^?1, respectively. In upper layers and subsoil of Kedah, average total Mo were 0.34 and 0.27 mg kg^?1, respectively. Average total Mo in Kelantan were 0.25 mg kg^?1 (surface layer) and 0.28 mg kg^?1 (subsoil). Cation exchange capacity (CEC) was positively correlated with plant available amounts of Mo in upper layers of Kedah area. Also, total and medium-term plant-available S was correlated with total carbon (C) at lower layers of Kelantan soil series. But in surface layers of Kelantan soil series, CEC was strongly correlated with total and medium-term plant-available S. Our results indicates that the influence of flooding conditions on soil S and Mo contents in paddy fields may cause long-term changes in S and Mo chemical reactivities.     

Interaction of dimeric horse cytochrome c with cyanide ion

We have previously shown that methionine–heme iron coordination is perturbed in domain-swapped dimeric horse cytochrome c. To gain insight into the effect of methionine dissociation in dimeric cytochrome c, we investigated its interaction with cyanide ion. We found that the Soret and Q bands of oxidized dimeric cytochrome c at 406.5 and 529 nm redshift to 413 and 536 nm, respectively, on addition of 1 mM cyanide ion. The binding constant of dimeric cytochrome c and cyanide ion was obtained as 2.5 × 10⁴ M^?1. The Fe–CN and C–N stretching (ν _Fe–CN and ν _CN) resonance Raman bands of CN^?-bound dimeric cytochrome c were observed at 443 and 2,126 cm^?1, respectively. The ν _Fe–CN frequency of dimeric cytochrome c was relatively low compared with that of other CN^?-bound heme proteins, and a relatively strong coupling between the Fe–C–N bending and porphyrin vibrations was observed in the 350–450-cm^?1 region. The low ν _Fe–CN frequency suggests weaker binding of the cyanide ion to dimeric cytochrome c compared with other heme proteins possessing a distal heme cavity. Although the secondary structure of dimeric cytochrome c did not change on addition of cyanide ion according to circular dichroism measurements, the dimer dissociation rate at 45 °C increased from (8.9 ± 0.7) × 10^?6 to (3.8 ± 0.2) × 10^?5 s^?1, with a decrease of about 2 °C in its dissociation temperature obtained with differential scanning calorimetry. The results show that diatomic ligands may bind to the heme iron of dimeric cytochrome c and affect its stability.