土壤中镉、铅、锌及其相互作用对作物的影响

通过作物盆栽模拟试验(砂壤质褐土、pH值8.2)揭示：土壤中分别施入镉(CdCl2)、铅[Pb(CH3COO)2]或锌(ZnSO4)其影响表现为,植物各器官镉的含量超过对照植物的数倍至500倍。土壤镉浓度<5ppm和<10ppm分别造成某些蔬菜和水稻的污染。铅主要积累在植物根部,土壤铅污染对作物的影响较小。锌主要积累在植物叶片和根部,对水稻产生生长抑制的土壤锌浓度临界值不大于200ppm,此浓度对旱作无影响。土壤中同时施入镉和铅,植物对镉的吸收增加。而土壤中镉的增加却减少了植物体内铅的含量。土壤中由于镉、锌或铅、锌相互作用的结果,水稻对它们的吸收都有增加。在旱地土壤锌浓度的增高,降低了植物对镉、铅的吸收。镉、铅、锌同时施入土壤由于相互作用的结果,除锌之外,植物对镉、铅的吸收有明显下降。评价土壤重金属污染,不仅要看它们的含量及其存在形态,而且要分析它们之间的相互作用(促进或拮抗)特点。     

Influence of cadmium and mercury on activities of ligninolytic enzymes and degradation of polycyclic aromatic hydrocarbons by Pleurotus ostreatus in soil

The white-rot fungus Pleurotus ostreatus was able to degrade the polycyclic aromatic hydrocarbons (PAHs) benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenzo[a,h]anthracene, and benzo[ghi]perylene in nonsterile soil both in the presence and in the absence of cadmium and mercury. During 15 weeks of incubation, recovery of individual compounds was 16 to 69% in soil without additional metal. While soil microflora contributed mostly to degradation of pyrene (82%) and benzo[a]anthracene (41%), the fungus enhanced the disappearance of less-soluble polycyclic aromatic compounds containing five or six aromatic rings. Although the heavy metals in the soil affected the activity of ligninolytic enzymes produced by the fungus (laccase and Mn-dependent peroxidase), no decrease in PAH degradation was found in soil containing Cd or Hg at 10 to 100 ppm. In the presence of cadmium at 500 ppm in soil, degradation of PAHs by soil microflora was not affected whereas the contribution of fungus was negligible, probably due to the absence of Mn-dependent peroxidase activity. In the presence of Hg at 50 to 100 ppm or Cd at 100 to 500 ppm, the extent of soil colonization by the fungus was limited.     

Effects of addition of varying levels of copper,as oxide or phosphate,on nitrogen mineralisation and nitrification during incubation of a slightly calcareous soil receiving dried blood

Summary The addition of 100, 1000 and 10,000 ppm copper, as oxide or hydrogen phosphate, stimulated nitrogen mineralisation and nitrification during incubation of a sandy loam (0.5% calcium carbonate) treated with 200 ppm N as dried blood. The maximum effects occurred with 1000 ppm added copper and were similar with both sources of added copper. EDTA-extractable copper was higher where copper hydrogen phosphate than where copper oxide had been added.     

Dose-related effects of dichloromethane on rat brain in short-term inhalation exposure

Male Wistar rats were exposed to 500, 1000 or 100 ppm as time-weighted average (t.w.a.) concentrations of dichloromethane vapour. The 1000 (t.w.a.) ppm exposure consisted of two 1-h peak concentrations (2800 ppm) on a basal exposure of 100 ppm. All exposures lasted for 6 h, 5 days weekly and for 2 weeks. The solvent burdens were analyzed in the perirenal fat samples which showed a relation to the dose with the highest values in the 1000 (t.w.a.) ppm exposures. The solvent concentrations increased in the perirenal fat between the two weeks of exposure. Blood carbon monoxide concentrations did not accurately reflect the body solvent burdens. Neurochemical effects also displayed a dose relationship, and included decreased succinate dehydrogenase activity in the cerebellum at the two higher doses and increased acid proteinase activity at 1000 ppm in the cerebrum. Withdrawal of the animals for 7 days from the 2-week exposure showed that the biochemical changes were largely abolished with the exception of decreased succinate dehydrogenase activity at 1000 ppm (t.w.a.).     

Differential effects of cadmium on blood lymphocyte subsets

This work was designed to analyze the possible dose dependent effects of cadmium on the blood lymphocyte subset distribution and if these effects are related to circulating cadmium concentration. For that purpose, adult male rats were exposed for one month to 0, 5, 10, 25, 50 or 100 ppm of cadmium chloride (CdCl2) in the drinking water. B lymphocytes decreased in peripheral blood with the doses of 5 and 10 ppm of CdCl2. From the dose of 25 ppm on, B cells increased. T lymphocytes were increased with the doses of 25, 50 and 100 ppm of CdCl2. The lower doses of the metal induced opposite effects. CD4+ and CD8+ cells decreased with the doses of 5 and 10 ppm whereas they were increased with the dose of 25 ppm of CdCl2 on. From the dose of 10 ppm on, cadmium concentration was increased. The results on the distribution of blood lymphocyte subsets suggest that cadmium inhibits the humoral and cellular immune response with the lower doses of the metal used, and opposite effects were detected with the higher doses, the effect not being dependent on the circulating cadmium.     

Oxidative stress and cholinesterase inhibition in saliva and plasma of rats following subchronic exposure to malathion

The aim of this study was to examine whether malathion, a commonly used organophosphate (OP), might induce oxidative stress and cholinesterase (ChE) depression in saliva and plasma in rats following subchronic exposure mimicking human exposure. Malathion was administered orally at doses of 100, 500 and 1500 ppm for 4 weeks. Oxidative stress was determined by measuring the malondialdehyde concentration, the end product of lipid peroxidation, and assessing total antioxidant power. Four weeks oral administration of malathion at doses of 100 ppm, 500 ppm and 1500 ppm depressed plasma ChE activity to 45% (P<0.01), 48% (P<0.01) and 41% (P<0.01) of control, respectively. Malathion at doses of 100 ppm, 500 ppm and 1500 ppm depressed saliva ChE activity to 73% (P<0.01), 75% (P<0.01) and 78% (P<0.01) of control, respectively. Malathion at doses of 100 ppm, 500 ppm and 1500 ppm increased plasma antioxidant power by 33% (P<0.01), 59% (P<0.01) and 118% (P<0.01) of control, respectively. Malathion did not change saliva antioxidant power. Malathion at doses of 100 ppm, 500 ppm and 1500 ppm increased plasma thiobarbituric acid reactive substances (TBARS) by 61% (P<0.01), 69% (P<0.01) and 63% (P<0.01) of control, respectively. Malathion at doses of 500 ppm and 1500 ppm increased saliva TBARS by 19% (P<0.01) and 22% (P<0.01) of control, respectively. Malathion (100 ppm) did not change saliva TBARS level. We concluded that in OP subchronic exposure, depression of ChE is accompanied by induction of oxidative stress that might be beneficial in monitoring OP toxicity.     

Boron,an essential micro-element forAzotobacter chroococcum

Summary 1. It was shown that boron is an essential micro-element forAzotobacter chroococcum.2. Multiplication, CO₂ production, N fixation and pigmentation are closely related to the boron content of the culture medium. Of these, pigmentation is most susceptible to slight boron deficiency; with an easily assimilable carbon source (mannite, glucose) nitrogen fixation seems to be more susceptible than multiplication to boron deficiency.3. With increasing gifts of boron, the CO₂ production curves in quartz sand with nutrients as well as in liquid cultures follow each other at regular sequences.4. The optimum boron content for normal development ofAzotobacter amounts toca 2 ppm in liquid cultures, to 5 ppm in quartz sand cultures, whereas in soils sometimes 8 ppm B are tolerated, without noticeable loss of activity.     

土壤镉污染与作物

通过土壤镉污染对作物影响的盆栽模拟试验,以揭示重金属镉在土壤—植物系统中的转移、分布规律及其对植物生长、发育的影响。试验证明不同化合形态的镉施入土壤(砂壤质褐土,pH值8.2),水稻对镉吸收的多寡依次为CdCl2>CdSO4>CdO>CdS>CdCO3。白菜的镉吸收表现为CdSO4>CdCl2>CdO>CdCO3。土壤的不同镉浓度(施加CdCl2,以纯镉计)对作物影响的试验结果表明,可食部位达到食品污染标准(谷物含镉量0.4ppm、蔬菜0.2ppm为暂定标准)时的土壤镉污染临界值分别为：小麦、莴苣、白菜<1ppm,茄子、萝卜<2.5ppm,番茄、菜豆<20ppm。土壤因子的处理影响镉的活动性;降低土壤pH值,水稻的镉吸收增加。增施有机肥、ZnSO4、S、CaO、CaSO4可降低糙米含镉量13.4%一30%。白菜的镉吸收,由于增施有机肥、FeSO4、Fe2O3、CaO或S而降低菜叶含镉量28%一61%。以Cd,Zn比1:100或1:200施入土壤,叶内含镉量分别下降61%和76.4%,但白菜产量减少61%和76%。     

Role of Bacillus licheniformis in Phytoremediation of Nickel Contaminated Soil Cultivated with Rice

Heavy metal contamination in soil is an important environmental problem and it has negative effect on agriculture. Bacteria play a major role in phytoremediation of heavy metals contaminated soil. In this study, the effect of Bacillus licheniformis NCCP-59, a halophilic bacterium isolated from salt mines near Karak, Pakistan, were determined on a three week old greenhouse grown seedling and germinating seeds of two rice varieties (Basmati-385 (B-385) and KSK-282) in soil contaminated with different concentrations (0, 100, 250, 500, and 1000 ppm) of Nickel. Nickel significantly reduced the germination rate and germination percentage mainly at 500 and 1000 ppm. Significant decrease in ion contents (Na, K, and Ca) was observed while Ni ion concentration in the plant tissues increases as the concentration of Ni applied increases. The photosynthetic pigments (chlorophyll a (chl a), chlorophyll b (chl b), and carotenoids) were also decreased by the application of different concentrations of Ni. Total protein and organic nitrogen were found to be reduced at higher concentrations of Nickel. Inoculation of Bacillus Licheniformis NCCP-59 improved seed germination and biochemical attribute of the plant under Ni stress. It is clear from the results that the Bacillus Licheniformis NCCP-59 strain has the ability to protect the plants from the toxic effects of nickel and can be used for the phytoremediation of Ni contaminated soil.     

The effect of abamectin seeds treatment on plant growth and the infection of root-knot nematode Meloidogyne incognita (Kofoid and White) chitwood

In this study, three concentrations (250, 500, and 1000 ppm) of abamectin 2% suspension concentration (SC) were used as cucumber seeds treatment. The seeds were treated with abamectin to reduce nematodes reproduction and their ability to penetrate the roots, then seed germination and plant growth were observed. All the concentrations didn’t negatively affect seeds germination wherever the germination percent reached 80% at the concentration (1000 ppm) after 20 days of sowing. The effect of abamectin on root-knot nematode was studied by recording numbers of nematodes in 100 g/soil, numbers of the galls, egg mass on the root, and the nematode reproduction factor. All concentrations significantly affected the nematode reproduction parameters compared to control. Abamectin at (500 ppm) was the most effective concentration on reducing nematodes parameters, i.e., 26.57, 38.83, 47.40 %, and 3.15 for the above-mentioned parameters, respectively at the end of experimint. No significant difference between 500 ppm and 1000 ppm. We recommended using the abamectin in (500 ppm) concentration as a seed application to control Meloidogyne incognita in cucumber plants under greenhouse conditions to reduce its environmental toxic effect.     

Incubation study on effects of adding varying levels of nickel (as sulphate) on nitrogen and carbon mineralisation in soil

The effects were studied of adding 10, 100 and 1000 ppm Ni (as sulphate) to a sandy soil (pH 5·9) on N and C mineralisation during subsequent aerobic incubation for 6 weeks at 30° C. With increasing Ni level, nitrification decreased to a greater extent than did N and C mineralisation. The toxic effects of 1000 ppm Ni were not much greater than those of 100 ppm Ni. Nitrification and N and C mineralisation were decreased by 68, 36 and 35% respectively with 1000 ppm Ni. Results are discussed in relation to exchangeable and EDTA-extractable Ni levels.     

Cadmium and Lead Accumulation in the Earthworm Eisenia fetida (Savigny) and its Impact on Cholinesterase and Metabolic Pathway Enzyme Activity

The uptake of cadmium and lead was studied in the earthworm Eisenia fetida (Annelida: Oligochaeta) using an artificial soil exposure. Although cadmium and lead are bioconcentrated in Eisenia fetida tissue, bioaccumulation is not shown for concentrations below 100 ppm for lead, individuals eliminating as much metal as they ingest or the interactions between lead and organic matter in our substratum reduce the bioavailability of lead at low concentration. The cholinesterase activity was not inhibited when individuals were exposed for 8 weeks to either 8 or 80 ppm of cadmium or 100 or 2,000 ppm of lead. Results are different from those reported in another species Eisenia fetida andrei (= E. andrei) showing an inhibitory effect of lead on ChE activity; thus, differences in cholinesterase inhibition reflects the existence of two separate species. No effect of cadmium and lead on the activity of esterases, malate dehydrogenase, phosphoglucomutase and glutamate oxalate transferase was found in our experimental conditions, but we observed the disappearance of the fast moving band after electrophoretic separation for phosphoglucose isomerase.     

The role of boron in plant response to mycorrhizal infection

Summary In a Morrison sandy loam marginal in boron, fertilization with 1.1 ppm boron increased the shoot dry weight of mycorrhizal red clover (Trifolium pratense L.) an average of 16%, but did not affect nonmycorrhizal clover weight. Root colonization and foliar phosphorus concentrations were not significantly affected by B deficiency. With alfalfa (Medicago sativa L.) and Morrison soil in which B deficiency had been intensified by the addition of 100 ppm nitrogen as NH₄NO₃, inadequate B reduced the shoot dry weight of mycorrhizal plants 71%vs a reduction of 35% for nonmycorrhizal plants. Boron deficiency was more severe in the earlier cuttings and delayed the onset of mycorrhizal infection and the subsequent spread of mycorrhizal fungi within the roots. This delay may contribute to the lower concentrations of P and Cu seen by others during early developmental stages of B-deficient alfalfa.     

Genotypic variability among peanut (Arachis hypogea L.) in sensitivity of nitrogen fixation to soil drying

Peanuts (Arachis hypogea L.) are often grown on sandy soils and drought stress can be a major limitation on yield. In particular, loss in nitrogen fixation activity associated with soil drying might be limiting due to the need for high nitrogen amounts in both vegetative tissues and seeds of peanut. This study examined the response of nitrogen fixation of intact plants of seventeen peanut genotypes when subjected to soil drying in pots over approximately a 2-wk period. A large range in the sensitivity of nitrogen fixation to soil drying was observed among the seventeen genotypes. Genotype ICGV86015, in particular, was found to have nitrogen fixation that was especially tolerant of soil drying. Significant positive (P?<?0.0001) correlation was found between the soil water content at which nitrogen fixation began decreasing and the amino acid concentration in the leaves of severely stressed plants.     

Effect of aldrin on nodulation,nitrogen fixation and yield of bengal gram (Cicer arietinum)

Summary The effect of aldrin on nodulation (nodule number and their dry weight) in bengal gram (Cicer arietinum) was not very clear. Aldrin decreased nitrogen fixation and yield at the concentration of 1, 5 and 10 ppm in soil. The application of farm yard manure eliminated completely the adverse effects on yield and partially, the adverse effects on nitrogen fixation. There was an increase in yield with the application of aldrin along with farm yard manure. Nodulation and nitrogen fixation at 1 ppm level of aldrin were more than control in presence of FYM. re]19760102     

Are cadmium effects on plasma gonadotropins, prolactin, ACTH, GH and TSH levels, dose-dependent?

It is well established that cadmium affects plasma levels of the pituitary hormones studied. However, whether the effects of the metal are dose dependent needs to be clarify. This work was designed to evaluate the possible changes in plasma levels of gonadotropins, prolactin, ACTH, GH and TSH after oral cadmium exposure in adult male rats. Plasma levels of these hormones were measured in adult male rats exposed to cadmium chloride (CdCl₂) in the drinking water at the doses of 5, 10, 25, 50 or 100 ppm for one month. The lower dose of cadmium increased plasma prolactin levels and higher doses of the metal (25 or 50 ppm) decreased them. There was a continuous increase of plasma ACTH levels from the lower to 25 ppm dose of CdCl₂ and decreased them after to basal values with the highest dose. Plasma GH levels were increased with the dose of cadmium of 10 ppm, although the doses of 5, 25 and 50 ppm decreased them. Plasma LH levels were only reduced with the dose of 50 ppm of CdCl₂, whereas those of FSH increased. Plasma TSH levels were increased with the doses of 5, 25 and 100 ppm of CdCl₂. Cadmium concentration increased in pituitary with the doses of 125, 50 and 100 ppm of CdCl₂. These data suggest that cadmium differentially affects the secretory mechanisms of the pituitary hormones studied depending on the dose used. The effects of the metal on prolactin and ACTH are dose-dependent.     

脲酶抑制剂氢醌对大豆结瘤、固氮和木质部溶质氮形态的影响

首次报导了在白浆土和砂壤土上使用氢醌(HQ)抑制土壤脲酶活性,有效地缓解尿素分解产物及其随后的氧化产物对大豆结瘤和固氮活性的抑制效应,结果表明:1.HQ浓度在40PPM以内对大豆幼苗生长及初生结瘤表现促进作用;进一步提高HQ浓度将使大豆根系生长受阻变态而阻止结瘤。2.HQ(10—50PPM)提高了离体活性大豆根瘤类苗体悬液的耗氧量(79.4—86.1％)和琥珀酸脱氢酶活性(124.7—138.4％)。3.盆栽和田间试验证实,由于HQ缓解了尿素的分解,从而颇大减轻了尿素对大豆结瘤和固氮(乙炔还原活性)的抑制效应;通过大豆木质部中溶质氮形态(酰胺、酰脲和硝酸盐)的分析进一步证实了,大豆植株从根部向地上部运输的氮素形态同土壤氮转化强度和根瘤固氮强度(酰脲相对丰度)之间的紧密联系。4.由于麦秸还田土壤脲酶活性提高,故应提高HQ剂量;与此同时,通过麦秸的“氮因子效应”便能完全解除尿素对大豆结瘤固氮的抑制,并为大豆籽实发育提供了丰富的土壤氮源。     

In situ Carica papaya stem matrix and Fusarium oxysporum (NCBT-156) mediated bioremediation of chromium

Removal of heavy metal chromium was carried out using the fungus Fusarium oxysporum NCBT-156 strain isolated from soil of leather tanning effluent in in situ condition using potassium dichromate solution with 10 per cent Czapek-dox liquid medium. Biosorbent matrix was developed using Carica papaya plant dry stem to colonize the fungal strain to facilitate bioabsorption process. Bioabsorption of chromium was by metabolically mediated intracellular accumulation process. Maximum efficiency of chromium removal by biosorption upto 90 per cent was achieved at the end of 5th day of incubation (120 h of contact time) for 100 and 200 ppm concentration, upto 80 per cent for 300 and 400 ppm, and upto 65 per cent for 500 ppm to 1000 ppm concentrations with pH ranging from 5.8, 5.6, 5.5, 5.4 and 5.2, respectively for 100, 200, 300, 400, 500-1000 ppm concentration. SDS-PAGE protein profile showed significant difference in 34 kDa protein band after chromium absorption by the fungus. FTIR spectroscopic analysis revealed that the main functional groups involved in the uptake of chromium by F. oxysporium strain were carbonyl, carboxyl, amino and hydroxyl groups.     

Effects of a soil conditioner on some physical and biological features of soils: results from a greenhouse study

A soil amendment substance-organic bio-stimulator, Terralyt Plus (TP), was used to observe its impact on the properties of clay loam (CL), sandy clay loam (SCL) and sandy loam (SL) soils and the growth of corn (Zea mays indentata L.) and wheat (Triticum aestivum ssp./vulgare Vill. v. lutescens) under greenhouse conditions. The diluted TP solutions (1:500, 1:1000 and 1:2000) were sprayed onto the soil surfaces. The wheat growth increased for CL and SCL with the application of TP at 1:1000. The highest dry weights were detected with 1:500 TP and corn in all the soils. Penetration resistance of CL containing corn increased with increasing TP concentration. TP was also effective in improving the aggregate stability for CL but not for the other soils. Catalase enzyme activity (CEA), soil evolution (SE) and the total aerobic bacterial population (TABP) were significantly increased (P<0.05) by spraying TP at 1:1000 onto CL.     

In vitro exposure of heavy metals on nucleotidase and cholinesterase activities from the digestive gland of Helix aspersa

Zinc, copper and cadmium are important environmental contaminants and differences in purinergic and cholinergic systems of invertebrates have been described when compared to characteristics of these signaling systems in vertebrates. Here we evaluate the effect in vitro of these metals on the ATPase, 5'-nucleotidase and cholinesterase (ChE) activities in the digestive gland of Helix aspersa. Zinc (500 and 1000 microM) promoted a significant decrease in 5'-nucleotidase activity. However, it did not induce changes in ATP hydrolysis. Copper (25 and 50 microM), inhibited significantly ATPase activity, but did not alter 5'-nucleotidase when compared to control (no metal added). In relation to effects of cadmium, an inhibitory effect on ATP hydrolysis has been observed at concentrations of 100, 500 and 1000 microM and a similar decrease of AMP hydrolysis was observed at 500 and 1000 microM. However, there were no significant changes in ChE activity from homogenates of the digestive gland of H. aspersa for all metals tested. This study demonstrated that zinc, cadmium and copper affect ATPase and 5'-nucleotidase in digestive gland, but not ChE, suggesting that the purinergic system may be a target related to toxicity induced by these metals and a possible indicator of biological impact of exposure to these contaminants.