Phytase inhibition by insecticides and herbicides

The effect of three herbicides (Linuron, Diuron, and Atrazine) and three vinyl phosphate insecticides (Crotoxyphos, Phosphamidon, and Dichlorvos) on phytase was examined. All the insecticides and Atrazine were competitive inhibitors, with Linuron and Diuron being mixed inhibitors. Some implications of phytase inhibition on inorganic P availability in soil are discussed.     

Neonicotinoid insecticides: oxidative stress in planta and metallo-oxidase inhibition

Neonicotinoids not only control insect pests but also sometimes independently alter plant growth and response to stress. We find that imidacloprid, thiacloprid, acetamiprid, thiamethoxam, and clothianidin but not nitenpyram and dinotefuran induce foliar lesions and peroxidative damage in soybean ( Glycine max ) seedlings assayed with the 3,3'-diaminobenzidine stain. The chloropyridinyl-carboxylic acid (COOH) but not the -carboxaldehyde (CHO) metabolites induce peroxidative damage but in a different pattern. Surprisingly, the chlorothiazolyl -CHO and -COOH metabolites induce chlorosis but no clear superimposable peroxidative damage or cell death. Four metallo-oxidases known to modulate reactive oxygen species were not sensitive in vitro to the parent neonicotinoid itself but were to several CHO and COOH metabolites and related compounds, with a sensitivity order of CHO > COOH and tyrosinase > xanthine oxidase and aldehyde oxidase > catalase. Although metallo-oxidase inhibition does not correlate overall with lesion formation, it may play an as yet unknown role in plant response to neonicotinoids.     

Inhibition of soil urease by organophosphorus insecticides

The effect of three organophosphorus insecticides on soil urease was examined. Inhibition of urea hydrolysis, some 60 days after application of 1000 parts/10⁶ of insecticide to a sandy clay loam, approached 40% (accothion) and exceeded 50% in the case of malathion and thimet. Similar inhibitory effects were recorded using a silt loam soil with which 200 parts/10⁶ application also produced inhibition ranging from 14% (accothion) to 23% (thimet) after 10 days. With lower concentrations of insecticide (50 parts/10⁶) inhibition, though again significant, was of a more ephemeral nature.All three insecticides, at a concentration of 1000 parts/10⁺⁶, prevented almost any hydrolysis of urea by jack bean urease. Ureolytic microorganisms, isolated from the soils under investigation, were inhibited by the organophosphates to a greater or lesser extent but the development of tolerance was common.It is suggested that the application of insecticides to control soil-borne insect pests may be a factor in determining the efficiency of urea fertilizer mineralization.     

缺磷对不同耐低磷玉米基因型酸性磷酸酶活性的影响

【目的】酸性磷酸酶活性与土壤及植株体内有机磷的分解和再利用有着密切的关系。本研究以不同耐低磷玉米自交系为材料,研究低磷胁迫下玉米叶片、根组织内以及根系分泌酸性磷酸酶活性的变化及基因型差异,探讨酸性磷酸酶与玉米耐低磷之间的关系,以期更深入地了解玉米耐低磷的生理机制。【方法】以5个典型耐低磷自交系99180T、99239T、99186T、99327T、99184T和2个磷敏感自交系99152S、99270S为试验材料,采用营养液培养方法,设正常磷和低磷两种处理,分别于缺磷处理3、8和12 d时调查取样,测定地上部干重、根干重、叶片中无机磷(Pi)含量、根和地上部磷累积量、根系分泌APase活性以及叶片中APase活性,并于缺磷处理12 d测定根系内APase活性。【结果】1)缺磷使玉米地上部干重下降,根干重、根冠比增加,随着缺磷处理(3 d→8 d→12 d)时间的延长,根干重、根冠比增加幅度增大,且耐低磷自交系根干重增加幅度普遍大于敏感自交系。2)低磷条件下,玉米自交系磷吸收、利用效率存在基因型差异,耐低磷自交系99239T、99180T和99327T磷吸收效率较高,99186T和99184T磷利用效率高,敏感自交系99152S、99270S磷吸收和利用效率均较低。3)低磷处理使玉米自交系叶片无机磷(Pi)含量显著下降,耐低磷自交系99184T、99327T和99239T下降幅度较小,相对叶片无机磷含量较高。4)缺磷诱导玉米根系分泌的APase活性升高。耐低磷自交系99184T和99186T根系分泌APase活性升高幅度较大,其余3个耐低磷自交系未表现出明显优势。缺磷处理3 d、8 d,玉米根系分泌APase活性与磷累积量显著正相关,而12 d时相关性不显著;根系分泌APase活性与磷利用效率在缺磷处理12d时达显著正相关。说明玉米根系分泌APase活性与磷吸收、利用效率相关关系不稳定。5)缺磷处理12 d,各玉米自交系根组织内APase活性与根系分泌APase活性变化情况较一致,两者相关系数r=0.755(P0.05)。6)缺磷条件下各玉米自交系叶片组织内APase活性均有升高趋势,并表现出明显的基因型差异。缺磷处理8 d,耐低磷自交系99184T和99239T叶片组织内APase活性升高幅度最大,其次是99327T和99186T,99180T、99270S和99152S升高幅度较小;缺磷处理12 d,各玉米自交系叶片APase活性仍继续增加,99239T、99184T、99327T和99186T的相对APase活性均较高,99270S和99152S的相对APase活性较低。相关性分析表明,缺磷条件下玉米自交系叶片中相对APase活性与叶片中相对无机磷(Pi)含量显著正相关,与磷吸收、利用效率不显著相关。【结论】低磷诱导玉米叶片、根组织和根系分泌APase活性升高,根组织和根系分泌APase活性的大小与玉米耐低磷能力不完全相关,叶片APase活性与玉米耐低磷能力有较好的一致性。     

柠檬酸盐和磷酸盐存在下酸性磷素酶在矿物和土壤胶体上的吸附

The aim of this work was to study the influence of phosphate and citrate, which are common inorganic andorganic anions in soils, on the adsorption of acid phosphatase by kaolin, goethite and the colloids separatedfrom yellow-brown soil (YBS) and latosol (LS) in central-south China. The YBS colloid has the major claymineral composition of 1.4 nm mineral, illite and kaolinite while the LS colloid mainly contains kaolinite andoxides. The adsorption isotherm of acid phosphatase on the examined soil colloids and minerals fitted tothe Langmuir model. The amount of enzyme adsorbed in the absence of ligands was in the order of YBScolloid ＞LS colloid＞kaolin≈goethite. In the presence of phosphate or citrate, the amounts of the enzymeadsorbed followed the sequence YBS colloid＞kaolin＞LS colloid＞goethite. The presence of ligands alsodecreased the binding energy between the enzyme and soil colloids or minerals. With the increase of ligandconcentration from 10 mmol L-1 to 400 m mol L-1, different behaviors for the adsorption of enzyme werefound in the colloid and mineral systems studied. A sharp decrease in enzyme adsorption was observed ongoethite while gradual decreases of enzyme adsorption were recorded in the two soil colloid systems. However,no any decrease was found for the amount of enzyme adsorbed on kaolin at higher ligand concentrations.When phosphate or citrate was introduced to the system before the addition of enzyme, the ligands usuallyenhanced the adsorption of enzyme. The results obtained in this study suggested the important role ofkaolinite mineral in the adsorption of enzyme molecules in acidic soils in the presence of various ligands.     

选用解磷菌剂改善缺磷土壤磷素的有效性

山西省大部分土壤为石灰性土壤,耕地土壤缺磷较严重,施入土壤的化学磷肥极易被固定,为了提高缺磷土壤磷素的有效性,分离筛选的B2和B67菌株研制的解磷菌剂(后称菌剂),首先接种到以磷酸三钙为唯一磷源的培养基中,液体速效磷含量比CK提高12.92倍和9.18倍,然后又接种到其它典型缺磷土壤中,可使土壤速效磷含量较CK增加1.35~3.04倍,且发现其溶磷效果和液体的pH值有关,也与土壤磷酸酶活性和有效活菌数相关,而且菌剂在提高土壤速效磷含量的同时,也提高了土壤速效钾的含量。另外菌剂在缺磷的盆栽和大田试验中取得相同效果,除显著提高土壤速效磷含量,培肥土壤外,同时还有改善作物农艺性状,提高作物产量的功效。     

Enhancement of acid phosphatase activity in Capsicum annuum L. plants in response to phosphate deficiency

This study examined acid phosphatase activity in the extracts of Capsicum annuum L. cv. ”︁Sweet Banana” seedlings grown axenically on water-agar medium or plants grown in a hydroponic system with or without phosphate. Initially, no elevated phosphatase activity was detected in the root surface, in root surface extractions or cell-free tissue extracts from plants that were not showing morphological symptoms of stress. Then elevated specific phosphatase activity was evident in all organ tissue extracts of the plants that showed signs of growth inhibition. The increase in specific activity in the cell free extracts of different organs appeared to be primarily the result of increased activity of the dominant isozyme present in all these extracts, instead of due to de novo synthesis of new isozymes. These and other experiments indicate the lack of phosphate starvation-inducible (psi) excreted phosphatase in Capsicum annuum L. cv. ”︁Sweet Banana”. Some limitations with the use of XP, 5-bromo-4-chloro-indolyl phosphate p-toluidine, particularly when incorporated into growth media and buffer with or without phosphate for the study of phosphate starvation-inducible excreted phosphatase activity were noted.     

Phosphate release from synthetic glasses and inhibition of phosphate fixation on ferric hydroxide

Release of phosphate from glasses in the systems basalt-K₃PO₄ granite-K₂SiO₃ Na₂SiO₃-apatite has been studied. Equilibrium leachate concentrations in water are attained in 3-5 hr (K⁺, 5-60 μg cm^-3; PO₄ ³-, 2-15 μg cm^-3). Glass composition, pH, and grain size influence solubility.

Phosphate fixation on freshly precipitated Fe(OH)₃ and on iron-rich laterites appear to be inhibited when glasses are rich in Na-K silicates. This may be due to surface modification of Fe(OH)₃ by the formation of sodium ferric silicates which are known to be stable at low temperatures.     

Sorption of phosphate by bayerite

The chemisorption of phosphate on aluminium hydroxide (bayerite) and its kinetics were studied. A rate equation was derived on the basis that each phosphate molecule replaces a surface hydroxyl group and binds directly to an aluminium atom. The rate constants were evaluated and the free energy change of the sorption reaction was calculated as 20.4 KJ/mol.     

Effect of insecticides on the availability of nutrients,nitrogen fixation,and phosphate solubility in the rhizosphere soil of rice

A field experiment was conducted to investigate the effects of 1,2,3,4,5,6-hexachlorocyclohexane (BHC), phorate, carbofuran, and fenvalerate, at their recommended doses, on some chemical and microbiological properties of the rhizosphere soil in relation to rice yields. In general, the insecticides had a beneficial effect on rhizosphere soil properties. Carbofuran strongly stimulated the mineralization of organic C. BHC and phorate led to the retention of less total N in the soil. BHC released more NH _inf4 ^sup+ -N than the other insecticides. Phorate, however, liberated the most NO _inf3 ^sup- -N. Phorate and fenvalerate released more available P than BHC and carbofuran did. All the insecticides stimulated the proliferation of aerobic non-symbiotic N₂-fixing and phosphate-solubilizing microorganisms, resulting in an overall increase in rice yield. BHC had the greatest effect on rice yields, followed by phorate.     

Analysis of vinyl chloride by mass fragmentography.

Vinyl chloride is analyzed by mass fragmentography by simultaneously recording its m/e 62 and 64 ions. The minimum quantity necessary for detection is 8.7 X 10(-12) g/10 ml injection. At this level the coefficient of variation is 8.51%.     

Adsorption and desorption of phosphate by soils

Abstract

Added P adsorbed, expressed as a percentage of total added P, was closely and inversely related to added P subsequently desorbed, expressed as a percentage of added P adsorbed. This relationship was not linear but followed a hyperbola‐like curve. For the limiting cases where adsorption was 0% and 100%, desorption was 100% and 0%, respectively. If desorption is the mechanism limiting the release of P into the soil solution for plant utilization, then the well‐established relationship between P adsorbed in the laboratory and the recovery of fertilizer P under field conditions is accounted for.     

Alkaline dissolution of starch facilitated by microwave heating for analysis by size-exclusion chromatography

A rapid, straightforward starch dissolution method was developed to facilitate analysis of starch by size-exclusion chromatrography (SEC). Soft wheat starch was dispersed in 6 M urea and 1 M KOH and subjected to heating for 35, 45, or 60 s in a microwave oven as a potential means of starch dissolution. An increase in microwave heating time enhanced starch solubility but resulted in a steady decrease in amylopectin peak area and a consequent, artifactual increase in the amylose peak area due to molecular degradation. However, microwave heating for 35 s afforded a reasonable separation of starch fractions by SEC while minimizing molecular degradation of starch in comparison to a traditional starch dissolution procedure. This procedure provides a fast (<30 min), simple, and reproducible starch dissolution method for preparation of starches for SEC analysis and represents the first successful report of direct dissolution of granular starch via microwave heating.     

Uptake of residual phosphate and freshly applied diammonium phosphate by Lolium perenne and Trifolium repens

Residual fertilizer phosphorus (residual P) may significantly contribute to crop P nutrition. To test this hypothesis, a pot experiment was conducted with ryegrass (Lolium perenne) and clover (Trifolium repens) grown separately on three different soils which either had not received P fertilizer for at least nine years (0F) or had received P fertilizer equivalent to crop P off‐take (F). Soils in the pot experiment were given either none (0F, F) or a single rate of 15 mg P (kg soil)^–1 as diammonium phosphate (0F+DAP, F+DAP). In the treatments 0F+DAP and F+DAP DAP had been labeled with ³³PO₄ while in the treatments 0F and F the pool of available soil P had been labeled with carrier‐free ³³PO₄. This allowed estimating the quantities of P in plant dry matter that derived from native soil P, residual fertilizer P or fresh fertilizer P. Fourteen to 62 % of the P in the above ground biomass of white clover or perennial ryegrass were derived from residual P whereas 7 to 28 % were derived from freshly applied DAP. The proportion of P derived from residual P was correlated to the total amount of P fertilizer added to the soils, while the proportion of P derived from DAP was correlated to the concentration of P in the soil solution of the 0F and F soils.     

Competitive degradation and detoxification of carbamate insecticides by membrane anodic Fenton treatment

The competitive degradation of six carbamate insecticides by membrane anodic Fenton treatment (AFT), a new Fenton treatment technology, was carried out in this study. The carbamates studied were dioxacarb, carbaryl, fenobucarb, promecarb, bendiocarb, and carbofuran. The results indicate that AFT can effectively degrade these insecticides in both single component and multicomponent systems. The carbamates compete for hydroxyl radicals, and their kinetics obey the previously developed AFT kinetic model quite well. Hydroxyl radical reaction rate constants were obtained, and they decrease in the following order: dioxacarb approximately carbaryl > fenobucarb > promecarb > bendiocarb > carbofuran. The AFT is shown to have higher treatment efficiency at higher temperature. Degradation products of the carbamates were determined by gas chromatography/mass spectrometry, and it appears that degradation can be initiated by hydroxyl radical attack at different sites in the molecule, depending on the individual structure of the compound. Substituted phenols are the commonly seen degradation products. The AFT treatment can efficiently remove the chemical oxygen demand of the carbamate mixture, significantly increasing the biodegradability. Earthworm studies show that the AFT is also an effective detoxification process.     

Isolation of Hemicellulose from Corn Fiber by Alkaline Hydrogen Peroxide Extraction

For the first time, alkaline hydrogen peroxide (AHP) extraction conditions were used to isolate hemicellulose (arabinoxylan) from destarched corn fiber. Yields of the water-soluble hemicellulose B ranged from 35% (24 hr extraction at 25°C) to 42% (2 hr extraction at 60°C). The hemicellulose B resulting from the 2 hr extraction (pH 11.5) was off-white in color, and a very low proportion (1.7%) of water-insoluble hemicellulose A was extracted. AHP treatment caused delignification and facilitated the alkaline extraction of hemicellulose from the lignocellulosic fiber matrix. In the absence of H₂O₂, yields were reduced by more than one-third when using otherwise identical extraction conditions of time, temperature and pH. In the standard protocol, corn fiber, NaOH solution, and H₂O₂ were mixed in a 1:25:0.25 (w/v/w) ratio. Extractions were conducted at pH 11.5 at 25°C or 60°C. The pH was adjusted to 11.5 by addition of NaOH at ambient and elevated temperatures. The optimum hemicellulose yield (51.3%; dry, starch-free basis) was obtained when the pH was increased to 12.5 for the final one-half of the extraction period. Products obtained after extraction at pH values greater than 11.5 were tan in color, however, and the goal of the research has been to isolate white hemicellulose B and then evaluate its properties. Under most conditions, the yields ofhemicellulose B, potentially the most useful form for food and industrial applications, exceeded those of hemicellulose A by more than 10-fold. The hemicellulose B products were lighter in color than those obtained using traditional alkaline extraction conditions of refluxing with calcium or sodium hydroxide. Steps prior to extractions with alkaline H₂O₂, such as grinding to 20 mesh and extracting with azeotropic toluene-ethanol, were found to be unnecessary.     

Organic phosphate sorption by neutral and basic soils

Abstract

The sorption of several organic phosphates were measured on soil, peat and other organic and inorganic materials. The behavior of the phosphates on these materials differed from that reported for similar studies on acidic soil materials. In contrast to the sorption on acidic soils, where sorption maxima occur, the sorption on basic soils may reach a maximum but does not decline thereafter. Both clay and organic matter content govern the amount of sorption but calcium seems to account for the differences observed from those on acidic soil materials     

Phosphorus fertilizer requirements as estimated by phosphate sorption

Abstract

Twenty‐nine soil samples representing 12 soil series and varying levels of P fertility were obtained from cooperating agricultural experiment stations in the southern U.S. Fertilizer P requirements were estimated from P sorption curves and correlated with P requirements established by field experiments. Estimated and measured P requirements were highly correlated (r =0.93**) with the quantitative relationship being nearly 1:1. With one exception, P sorption also accurately estimated needs of fertilized soils; in that one case, fertilizer needs were estimated at 45 kg P/ha although there was no response to P in the field.

The quantity of sorbed P in equilibrium with 0.02 μg P/ml apparently was a good estimate of fertilizer P requirement. The value 0.02 was somewhat lower than has been reported from other research; this lower value may be associated with somewhat lower yields, warm soil temperatures, and relatively long growing season in the southern U.S.A. It also may have been caused by under‐evaluating the effectiveness of residual fertilizer P or by a more stable P concentration in soil solution for soils receiving long‐term applications of fertilizer P.