Control of arsenic toxicity in rice plants grown on an arsenic‐polluted paddy soil

Abstract

Paddy soils of over 500 hectares had been polluted by arsenic (As) from tailings at an abandoned lead‐zinc mine at Shaoxing, Zhejiang, China. Several field experiments were conducted to establish measures for reducing As toxicity to rice plants. The results obtained were as follows. Fresh Chinese milkvetch (Astragalus sinicus L.) was not supposed to be used as green manure in arsenic polluted paddy soils. Although liming (1,500 kg CaO hectare^‐1) could reduce water‐soluble As (H₂O‐As) in the soil, the rice plant grew badly. The treatments of FeCl₃ (25 mg Fe kg^‐1 soil) and MnO₂ (25 mg Mn kg^‐1 soil) could markedly lower the H₂O‐As and arsenite [As(III)] percentage in the soil and make the plant grow better than the control experiment (CK). Without adding any materials to the soil, wetting and drying (furrowing and draining) in the paddy soil could increase soil redox potential greatly and lower the H₂O‐As and As(III) percentage obviously leading to better rice growth. In addition, the As contents of roots, flag leaf, grain, and husked rice of 11 new cultivare of early rice were determined and correlation analysis was conducted. Uptake and accumulation of As in different parts of cultivars Zhefu‐802 and Erjiufeng at the 4 As levels of the paddy soil demonstrated that the As contents in husked rice of both cultivars exceeded the hygienic standard (0.7 mg As kg^‐1) when they grew in the paddy soil having total As content of about 70 mg kg^‐1 for Zhefu‐802 and 100 mg kg^‐1 for Erjiufeng, respectively.     

Nitrogen accumulation in nodulated and non‐nodulated pea plants,grown in a sandy soil at different acidities

Abstract

The growth of nitrate‐supplied and dinitrogen‐fixing pea plants was studied in a pot experiment with a sandy soil in a pH‐H_?O range from 3.4 to 5.6. Optimum growth in both treatments occurred at pH 5.0. At low pH, N₂‐plants yielded significantly less than NO₃‐plants. Planting of nodulated seedlings did not enhance yield in comparison with sowing in inoculated soil, indicating that nodulation was not the most sensitive process in restricting yield. Comparison of the nitrogen contents of shoots of planted and sown N₂‐plants allowed the suggestion that the synthesis of nitrogenous compounds was also not limiting yield. At low pH, root growth was severely reduced in dinitrogen‐fixing plants in comparison with nitrate‐supplied plants. This difference could be explained by the influence of the form of nitrogen nutrition on the cation‐anion uptake pattern of the plant and the resulting pH‐shift in the rhizosphere. It is to be expected that in an acid soil under field conditions the indirect effect of nitrate on root growth and nodulation via increase of the pH is more extensive than its direct negative effect on nodulation.     

The effect of biochar addition on N2O and CO2 emissions from a sandy loam soil – The role of soil aeration

Biochar application to soil has significant potential as a climate change mitigation strategy, due to its recalcitrant C content and observed effect to suppress soil greenhouse gas emissions such as nitrous oxide (N₂O). Increased soil aeration following biochar amendment may contribute to this suppression.Soil cores from a Miscanthus X. giganteus plantation were amended with hardwood biochar at a rate of 2% dry soil weight (22 t ha⁻¹). The cores were incubated at three different temperatures (4, 10 and 16 °C) for 126 days, maintained field moist and half subjected to periodic wetting events. Cumulative N₂O production was consistently suppressed by at least 49% with biochar amendment within 48 h of wetting at 10 and 16 °C. We concluded that hardwood biochar suppressed soil N₂O emissions following wetting at a range of field-relevant temperatures over four months. We hypothesised that this was due to biochar increasing soil aeration at relatively high moisture contents by increasing the water holding capacity (WHC) of the soil; however, this hypothesis was rejected.We found that 5% and 10% biochar amendment increased soil WHC. Also, 10% biochar amendment decreased bulk density of the soil. Sealed incubations were performed with biochar added at 0–10 % of dry soil weight and wetted to a uniform 87% WHC (78% WFPS). Cumulative N₂O production within 60 h of wetting was 19, 19, 73 and 98% lower than the biochar-free control in the 1, 2, 5 and 10% biochar treatments respectively. We conclude that high levels of biochar amendment may change soil physical properties, but that the enhancement of soil aeration by biochar incorporation makes only a minimal contribution to the suppression of N₂O emissions from a sandy loam soil. We suggest that microbial or physical immobilisation of NO₃⁻ in soil following biochar addition may significantly contribute to the suppression of soil N₂O emissions.     

The influence of soil aeration on growth and elemental absorption of greenhouse‐grown seedling pecan trees

Abstract

‘Dodd’ pecan seedlings were exposed to 3 levels of soil aeration for 30 days; 100%, 5%, and 0% of the container surface exposed to the atmosphere. These treatments resulted in about 21%, 13.5%, and 3% soil O₂and 0.3%, 5%, and 13% soil CO₂for 100%, 5%, and 0% of the container surface exposed, respectively. Restricting soil aeration induced partial stomatal closure, and decreased leaf number, leaf area, and leaf, trunk and root dry weights. The decrease in root dry weight associated with reduced soil aeration exceeded the decrease in top dry weight by about 50%. Translocation of N and P to the leaves was reduced when soil aeration was restricted, but root N and P concentrations were increased compared to trees grown in well aerated soil. Leaf elemental concentrations of Ca, Mg, and Mn were lower when trees were exposed to reduced soil aeration. Zinc and Fe concentrations were greater in the roots of trees with low aeration, but leaf and trunk concentrations of Zn and Fe were not affected     

Effect of α-casein on DNA adsorption by Andosols and by soil components

Andosols and the soil components (allophanes, humic acids, and goethite) had been autoclaved to destroy the nuclease activity of soil microflora. DNA adsorption by allophanes and Andosols was decreased by increasing the amount of α-casein added to the allophanes and to soils up to casein concentration of 5 mg ml^?1. DNA adsorption by humic acids was significantly increased by increasing the amount of α-casein up to 1.0 mg ml^?1, whereas the addition of 20 mg α-casein ml^?1 completely blocked DNA adsorption. These results can explain why the addition of excess skim milk is operationally needed for effective DNA extraction from Andosols. The amount of DNA adsorbed by Andosols treated with dephosphorylated α-casein was significantly higher than that of not treated Andosols (p?相似文献   

Changes in nitrogen and phosphorus concentrations of silicon‐fertilized rice grown on organic soil 1

Rice grown on the organic soils of the Everglades is routinely fertilized with silicon (Si). The objective of this research was to investigate changes in nitrogen (N) and phosphorus (P) concentration in various plant parts in response to Si fertilization. Two cultivars were grown in lysimeters filled with low‐Si soil. Half the lysimeters were fertilized with calcium silicate to provide 2Mg Si ha^‐1 and the other lysimeters remained unfertilized as a control. Nitrogen concentration decreased in all plant parts with Si fertilization. Phosphorus concentration increased with Si. Maturity was earlier in the Si fertilized rice.     

Strategies to mitigate the adverse effect of drought stress on crop plants—influences of soil bacteria: A review

Drought stress affects plant growth and causes significant issues in meeting global demand for food crops and fodder. Drought can cause physiological, physicochemical, and morphological changes in plants, which negatively affects plant growth and productivity. To combat this under the increasing global threat of water shortage and rapid population expansion, it is crucial to develop strategies to meet global food demands. Plant growth-promoting rhizobacteria (PGPR) may provide a safe solution to enhancing crop yields through various mechanisms. These soil bacteria can provide drought tolerance to crop plants, allowing them to survive and thrive in water-scarce conditions. Productions of phytohormones, free radical-scavenging enzymes, and stress-combating enzymes that can increase tolerance to drought-induced stress are key features of plant-associated microbial communities. This review summarizes the beneficial properties of microbes that help plants tolerate water scarcity and highlights the bacterial mechanisms that enhance drought tolerance in plants.     

Effects of potassium silicate and nanosilica on quantitative and qualitative characteristics of a commercial strawberry (fragaria × ananassa cv. ‘camarosa’)

Silicon (Si) is considered as a beneficial element to higher plants especially under stress conditions. A factorial experiment, in a completely randomized design with four replications, was used to investigate the effects of two application methods (spraying and soil drenching) and eight levels of Si compounds including 0, 5, 10 and 15 mM of potassium silicate (K₂SiO₃) and 0, 5, 10 and 15 mM of nanosilica (SiO₂). The results indicated that Si application (all or some treatments) decreased transpiration, specific leaf area, petiole length, and promoted the flowering, fruit firmness, leaf/crown number, fresh and dry weight of shoot and root, water use efficiency. They also showed it did not affect the fruit set percentage, yield, chlorophyll index, total soluble solid, leaf area, fresh and dry weight of crown, photosynthesis, stomatal conductance, internal carbon dioxide (CO₂) concentration and mesophyll efficiency of strawberry. The results suggest the beneficial effects of Si on growth and development of strawberry.     

Assessing soil biological characteristics: a comparison of bulk soil community DNA-, PLFA-, and Biolog™-analyses

Soil microbiological analyses may serve as a means for assessing soil characteristics. Standard microbiological culture-techniques, however, leave over 90% of the microorganisms in the environment unaccounted for. Several more recently developed analytical techniques such as DNA, phospholipid fatty acid (PLFA), and community level substrate utilization (CLSU) fingerprints allow for more detailed analyses of soil microbial communities. We applied analyses of (1) community DNA with PCR and restriction fragment length polymorphism (RFLP), (2) community PLFAs with gas chromatography and mass spectrometry, and (3) CLSU with Biolog™ gram-negative-plates, to evaluate the biological characteristics of three soils used in pesticide degradation studies. Each of these methods analyzes a different aspect of soil microbial characteristics. A protocol was developed for the statistical comparison and combination of the data from all the analyses, thus allowing for a polyphasic approach to biological soil characterization. We found that all three methods yielded highly reproducible results for each soil and allowed to distinguish the soils based on the structures of specific gene- and PLFA-pools as well as on CLSU fingerprints. Not all methods, however, revealed the same relative similarities of the three soils based on cluster analysis of the biological characteristics. These results demonstrate the value of comparative data analyses and indicate that biological soil characterization needs to be interpreted with caution if it is performed with one method only.     

Yield of iron‐sprayed and non‐sprayed strawberry cultivars grown on high ph calcareous soil

Abstract

Iron (Fe) deficiency chlorosis (FeDC) results in extensive reduction in yield of strawberry (Fragaria x ananassa Duch.) grown on high pH calcareous soils. Three cultivars differing in response to FeDC were grown on a high pH (8.2) calcareous soil (25.4% calcium carbonate equivalent in surface 20 cm) in the field (Choueifat, coastal area of Lebanon) to determine the effects of FeDC on fruit yield of cultivars sprayed with FeEDDHA [ferric ethylene‐diiminobis (2‐hydroxyphenyl) acetate]. The unsprayed plots were used as a control. No significant interaction (P<0.05) between cultivars x FeEDDHA spray treatment, and no significant differences (P<0.05) between one and two FeEDDHA spray(s)/week treatment was noted for visual FeDC, fruit number, and fruit yield. Sprayed cultivars once a week produced higher yields than unsprayed ones; overall increases were 33% (13% for ‘Motto’, 30% for ‘Chandler’, and 56% for ‘Douglas'). Even though only slight FeDC was noted on the ‘Motto’ cultivar receiving no Fe EDDHA spray, fruit yields were increased when sprayed with FeEDDHA. However, significant increases in yield for ‘Chandler’ and ‘Douglas’ cultivars with severe FeDC ratings were rioted when sprayed with FeEDDHA.     

Effects of soil type,mineral nutrition and salinity on greenhouse‐grown muskmelon in winter 1

Greenhouse experiments under winter conditions were conducted to examine the effects of soil type, mineral nutrition and salinity on vegetative growth and. fruit yield of ‘Galia’ muskmelon (Cucumis melo L.). Growth in a calcareous soil or in sand, under low nutrition level or with 200 mM NaCl added during fruit maturation, imposed significant stresses on the plants expressed by (a) a decrease in dry matter accumulation in vegetative organs, in fruit number and size, and (b) an increase in dry matter percentage in leaf blades and stems. Despite the significant differences in vegetative growth of plants grown in heavy soil vs sandy soil, and in high nutrition vs low nutrition levels, the distribution of dry matter among vegetative organs (leaves, stems and roots) was affected only slightly. Sandy soil, low nutrition and high salinity decreased branching, and thus the distribution of dry matter between the main shoot and the branches. Dry matter percentage in leaf blades and stems was a sensitive parameter which increased under soil, nutrition or salinity stresses. Fruit netting and total soluble solids (TSS) content were significantly decreased by sandy soil and low nutrition level. Application of salinity during fruit growth increased both netting and TSS.     

Studies on the ecology of actinomycetes in soil—VIII: Distribution and characteristics of acidophilic actinomycetes

Acidophilic actinomycetes, growing between pH 3.5 and 6.5, were isolated from 17 natural soils and mine wastes. Most isolates were Streptomyces spp. and selected ones were compared with some established neutrophilic species by assessment of overall similarity. Acidophilic and neutrophilic strains clustered separately, differing in a number of cultural and physiological characters, in addition to pH requirements. The possible importance of acidophilic actinomycetes in soil is discussed.     

Effects of long‐term applications of various nitrogen sources on chemical soil properties and composition of bromegrass hay

Effects of 15 annual applications (from 1979 to 1993) of ammonium nitrate (AN), urea, ammonium sulfate (AS), and calcium nitrate (CN) applied at 168 and 336 kg N ha^‐1 to bromegrass (Bromus inermis Leyss.) on soil acidification, and concentration of aluminum (Al), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) in soil and in hay were investigated in a field experiment on a thin Black Chemozemic (Typic Boroll) soil in Alberta, Canada. Soil was acidified and the concentration of extractable Al, Fe, and Mn was increased by nitrogen (N) application, but the magnitude varied with N source. Soil acidification was greatest with AS, followed by AN and urea, with no effect of CN. At 336 kg N ha^‐1 rate, soil was acidified to a depth of 10, 15 and 30 cm with urea, AN AS, respectively. Soil acidification was also greater at 336 kg than 168 kg N ha^‐1. The CaCl₂‐extractable Al and Fe in the 0–15 cm layer increased with N application, which closely followed the decrease in soil pH from various N sources. Extractable Al and Fe concentration in the 15–30 cm layer increased in response to reduction in soil pH by AS only, and there was no change in the extractable Al and Fe below the 30‐cm depth by any form of N. The DTPA‐extractable Mn in soil generally changed in response to N application. There was no effect of N source on the DTPA‐extractable Zn and Cu in soil. When soil pH had been lowered from N application, the concentration of Al in hay decreased while Zn concentration increased. The Mn concentration in forage increased markedly in response to reduced soil pH from application of AN, urea and AS. There was no effect of N fertilization on the Cu and Fe concentration in hay. In conclusion, the magnitude of soil acidification, changes in the Al, Fe, and Mn concentrations in soil and changes in the Al, Zn, and Mn concentrations in bromegrass hay varied with N source. The results suggest the need for periodic monitoring of soil pH and consideration of liming costs in the economics of various N fertilizers.     

Negligible effect of X-ray μ-CT scanning on archaea and bacteria in an agricultural soil

X-ray Microfocused Computed Tomography (X-ray μ-CT) allows a non-destructive and three-dimensional observation of microbial habitats (i.e. pore space) in soil. A major premise for microbiological studies integrating X-ray μ-CT is that soil microorganisms are not affected by irradiation dose in terms of physiology and composition. However, the compatibility of X-ray μ-CT and soil biological experiments has been evaluated controversially.We performed an incubation experiment with packed microcosms to assess the effect of X-ray μ-CT on native microbial populations with emphasis on soil archaea and bacteria. Before (14 days) and after (1 and 14 days) scanning we analyzed (i) respiration, (ii) enzyme activity, (iii) microbial biomass, (iv) abundance and (v) community structure in scanned and control treatments.None of the microbial parameters exhibited significant differences among scanned and unscanned soil samples at all sampling times with the exception of lower archaeal cell numbers subsequent to X-ray μ-CT. Incubation time was the main factor that induced a significant alteration of microbial soil populations while irradiation had no or only very little effect thereupon. Taken together, three-dimensional in situ data obtained via X-ray μ-CT may well be combined with microbiological analyses in soil.     

Effect of fused magnesium phosphate on paddy grown on “akiochi” soil with particular reference to phosphorus and silicon

In order to increase the p:tady prodution of our country, a better fertilizer practice is needed Particularly in the low productive areas known as “akiochi” fields which are now said to occupy about one fifth of the whole paddy areas in Japan.     

Comparison of the α-amylase inhibitor-1 from common bean (Phaseolus vulgaris) varieties and transgenic expression in other legumes--post-translational modifications and immunogenicity

The seeds of peas (Pisum sativum) and chickpeas (Cicer arietinum) expressing a gene for α-amylase inhibitor-1 (αAI) from the common bean (Phaseolus vulgaris) are protected from damage by old world bruchids (pea and cowpea weevils). Here, we used electrospray ionization time-of-flight mass spectrometry to compare the post-translational modifications of αAI from transgenic sources with the processed forms of the protein from several bean varieties. All sources showed microheterogeneity with differences in the relative abundance of particular variants due to differences in the frequency of addition of glycans, variable processing of glycans, and differences of C-terminal exopeptidase activity. The structural variation among the transgenics was generally within the range of the bean varieties. Previously, mice showed allergic reactions following ingestion of transgenic pea αAI but not bean αAI. Here, only minor differences were observed following intraperitoneal sensitization. Both of the transgenic pea and bean forms of αAI elicited Th1 and Th2 antibody isotype responses, suggesting that both proteins are immunogenic and could potentially be allergenic.     

Mechanism of manganese toxictty and tolerance of plants VII. effect of light intensity on manganese‐induced chlorosis

Effect of light intensity on Mn‐induced chlorosiss was investigated with bush bean (Phaseolus vulgaris L.) and corn (Zea mays L.) seedlings. The seedlings were grown in nutrient solutions containing different concentrations of Mn in enclosures which transmitted different percentages of the total solar radiation. At high levels of Mn in nutrient solution, the increase in light intensity increased the Mn uptake by the plant and resulted in a decrease in the chlorophyll content of the leaves. Even at similar levels of Mn concentrations within the leaves, high light intensity increased the severity of Mn‐induced chlorosis.

Photobleaching experiments were carried out with isolated chloroplasts suspended in media containing 0, 10^‐4 , 10^‐3,10^‐2 and 10^‐1 M Mn²⁺. Addition of Mn²⁺ to the medium decreased the extent of photobleacing of chlorophyll with increaing Mn²⁺ concentration up to 10^‐3 M . In concentrations of Mn²⁺ higher than 10^‐3 M, the extent of bleaching was increased again, accompanied by precipitation of oxidized manganese in the medium.

It is suggested that high light intensity stimulates not only the Mn uptake by the plant but also the destruction of chlorophyll when Mn in excess.     

Effect of extractable zinc,phosphorus, and soil ph on zinc concentrations in leaves of field‐grown corn

Abstract

The variability in corn yield responses to applications of Zn fertilizer appears to be associated with several complex soil and climatic factors that affect the availability of endogenous soil Zn to the crop under specific conditions. Among the soil chemical properties that influence availability of endogenous Zn are soil pH, organic matter content, and extractable P. Over a period of several years, soil and plant analysis data were collected from 54 field experiments, field trials, and diagnostic visits to producer's fields. These data were subjected to multiple regression analysis, resulting in an equation: Zn_leaf = 37.14 + 1.513 Zn_st ‐4.04 pH_st ‐ 1.791 ln(P_st/100) where Zn_st, pH_st, and P_st were 0.1N HC1 extractable soil Zn (kg/ha), 1:1 soil‐water pH, and Bray's 1 extractable soil P (kg/ha), respectively. These factors accounted for 67% of variation in leaf Zn, which was a large portion of the variability in Zn_leaf considering that climatic conditions, management levels, and varietal differences were uncontrolled in most instances. Using the previously published critical level in the leaf opposite and below the ear as 17 μg Zn/g, these data can be used to set required soil test levels of Zn at different levels of extractable P and soil pH. Inadequate levels of extractable Zn would range from 2.5 (at pH 6.0, P = 70 kg/ha) to, 9.5 kg/ha (at pH 7.5, P = 420 kg/ha).     

Effect of nitrogen and phosphorus on ‘delicious’ apple trees grown in caliche soil in the greenhouse

Abstract

In a greenhouse study, mono‐ammonium phosphate applications to ‘Delicious’ (Oregon spur cv) apple trees, Malus domestica Borkh., improved a low‐vigor condition associated with a caliche soil. The moderate rate of mono‐ammonium phosphate (6 grams per tree) resulted in trees with greater shoot extension, leaf numbers, a higher percent leaf phosphorus, and less purple leaf margins or spots than other soil treatments or the control. By September, trees treated with the highest rate of mono‐ammonia phosphate (12 grams per tree) had the highest level of leaf phosphorus and significantly higher levels of leaf phosphorus than all forms of nitrogen‐only fertilizer (ammonium nitrate, ammonium sulfate, calcium nitrate, and urea). In most cases, applications of the nitrogen‐only fertilizers, reduced leaf phosphorus levels throughout the experiment.     

Toxic concentrations of iron and manganese in leaves of Phaseolus vulgaris L. growing on freely‐drained soils of pH 6.5 in Northern Tanzania

Abstract

A bronzing symptom of trifoliolate leaves of Phaseolus vulgaris is described which has been found to be widespread on the southern slopes of the Meru and Kilimanjaro massifs in northern Tanzania. The symptom occurred on plants growing on freely draining soils of moderate pH and has led to complete loss of yield of badly affected plants. Leaves with the bronzing symptom contained large concentrations of iron (>3080 mg/kg) and manganese (>760 mg/kg) considered to be toxic in Phaseolus plants.