Polarographic investigation of binding of Cu++ and Cd++ by DNA

The equilibrium binding constants of Cd⁺⁺ and Cu⁺⁺ to native and denatured calf thymus DNA were determined polarographically. The binding constants are an exponential function of the potential at the binding site and as such they vary with ionic strength and with the charge on the DNA molecule. The correlation between the fraction of sites occupied by heavy metal ions and between the thermal stability of DNA in solution is discussed.     

Retention of Panjet‐applied alcian blue by cyprinids

Panjet‐applied alcian blue did not produce a reliable long‐term (> 5 months) mark. Average time to mark loss was 9·5 months for chub Leuciscus cephalus, 6·0 months for dace Leuciscus leuciscus and 11·1 months for roach Rutilus rutilus. Growth rate did not influence retention.     

Retention and absorption of foliar applied Cr

Summary Direct contamination studies of bean and lettuce leaves using single drops or spraying under controlled environmental conditions indicate that Cr whether it is applied as CrCl₃ or Na₂CrO₄ penetrates the leaves and accumulates at the treated areas without any significant translocation away from that area. The fractions retained or which could subsequently be washed or exchanged varied with the form of the salt. This publication is contribution no. 843 of the EURATOM Biology Division. This publication is contribution no. 843 of the EURATOM Biology Division.     

Accumulation of Cu++ onto modified bone-gelatin beads

1 Summary Cu²⁺ adsorbs onto modified bone gelatin beads as a function of pH. The amount of Cu²⁺ adsorbed is similar to that which has been shown to be adsorb onto other biological materials including bacterial biomass. Langmuir adsorption isotherms were fitted to this data and both the asymptotic maximum solid-phase concentration and the equilibrium constant for these isotherms are presented as a function of the solution pH. The adsorption rate for a typical set of experimental conditions is presented.Research supported by the Office of Basic Energy Scineces, Divisions of Engineering and Geosciences. U.S. Department of Energy under contract DE-AC05-84OR21400 with Martin Marietta Energy Systens, Inc.     

Ammonia volatilization from applied nitrogen in alkali soils

Incubation studies in a highly alkali soil showed ammonia volatilization losses from applied nitrogen to be largely governed by pH/alkalinity of the system. Submergence of the soil decreased the pH value resulting in lower losses. The anion of ammonium did not influence the losses. Ammonia volatilization obeyed first order kinetics. The losses were considerably reduced by deep placement of urea but were unchanged with variation in temperature from 20° to 40°C. Urea or ammonium sulphate lost similar amounts of nitrogen. Losses from green manure were very low. The results are discussed for their implication in nitrogen fertilizer efficiency and management in alkali soils.     

Retention of amylase in the secretory granules of parotid gland after extensive release of Ca++ by ionophore A-23187

The effect of the ionophore A-23187 was tested on isolated secretory granules of rat parotid gland. The ionophore caused extensive release of calcium from the granules without effecting release of amylase or other secretory proteins. It is therefore concluded that the role of calcium in the granules is probably not that of a stabilizing agent.     

Inhibition of photosystem II activity by Cu++ ion. Choice of buffer and reagent is critical

Cupric ion (Cu⁺⁺) inhibits the rate of photosystem II electron transport and the intensity of the variable part of chl a fluorescence in isolated chloroplast thylakoids. The inhibition is markedly dependent on the nature of the buffer used in the assay medium. In MES and HEPES buffers, complete inhibition of photosystem II occurs at 30 M of Cu⁺⁺, while in Tricine no inhibition occurred even at 200 M Cu⁺⁺. In other buffers used (TES, Phosphate, Tris), the efficacy of Cu⁺⁺ inhibition is intermediate. The calculated binding constants are found to correspond to the observed I₅₀ values for the six buffers used. It is concluded that the previous reports on copper inhibition, where buffers have been used indiscriminately should be reconsidered. Certain reagents such as hydroxylamine, ascorbate and diphenyl carbazide, which react with Cu⁺⁺, should be avoided.Abbreviations Chl chlorophyll - DCIP 2,6-dichlorophenol indophenol - DCMU 3-(3,4 dichlorophenyl)-1,1-dimethyl urea - DAD diaminodurene - DPC diphenyl carbazide - Fv variable chl fluorescence - HEPES N-2-hydroxyethyl piperazine sulfonic acid - I ₃₀ inhibitor concentration causing 30% inhibition of Fv - MES 2-(N-morpholino) ethane sulfonic acid - MV Methyl viologen - PS II Photosystem II - PS I Photosystem I - TES N-tris(hydroxymethyl)-methyl-2-amino sulfonic acid - TMPD N,N,N,N-tetramethyl-p-phenylenediamine - Tricine N-tris(hydroxymethyl) ethylglycine - Tris N-tris(hydroxymethyl)amino ethane     

The volatilization of ammonia from cattle urine applied to soils as influenced by soil properties

The amounts of ammonia volatilized, following the application of cattle urine to 22 soils, were measured in the laboratory during an incubation period of 10 days. The urine contained 12.0 g N dm^-3 and was applied to small columns of soil at a rate equivalent to 26.5 g N m^-2. The soils were from fields of both grassland and arable cultivation and varied widely in properties. Ammonia volatilization ranged from 6.8 to 41.3% of the total urinary N, with a mean value of 26.4%. The soil property most closely related to the extent of volatilization was cation exchange capacity (CEC), and this was so whether all 22 soils were considered together or whether the 14 grassland and 8 arable soils were considered separately. In general, the higher the CEC the less the amount of ammonia volatilized. However, for a given value of CEC, volatilization tended to be greater from a grassland than from an arable soil. The pH of a soil/urine mixture measured after 24 hours was also quite closely correlated with the amount of ammonia volatilized, but the initial pH and titratable acidity of the soil were poorly correlated with ammonia volatilization. ei]H Marschner ei]H Lambers     

Transformation of applied phosphorus in soils under rice-wheat cropping sequence

Summary The transformation of phosphorus in a rice-wheat cropping sequence was studied on alluvial, black, red and laterite soils of India. Phosphorus applied to rice increased Al-P and Fe-P in all soils, R-P in alluvial, black and laterite, and Fe-P and Ca-P in laterite soil only, while it increased native Fe-P in black and red soils. Phosphorus applied to rice and recovered as Al-P was higher after wheat than after rice in alluvial, red and laterite soils. In alluvial and laterite soils, the sum of total inorganic phosphorus fractions in no-P treatment was almost the same after the harvest of rice or wheat, while in black and red soils it was lower after wheat than after rice.     

Fractionation of applied 32P labeled TSP in calcareous soils

Calcareous dark brown red soil (calcixerollic xerochrept) from northern Syria was used in a pot experiment to study the fate of triple super phosphate fertilizer (TSP) with and without a crop (local durum wheat [Triticum turgidum L. group durum (Desf.)] cv. Bohouth). The soil received 17 μg P/g soil of ³²P-labeled TSP, and samples were collected from soils and plants at successive dates. Soil inorganic P was ≈?94% of total soil P, with only 50–80% being soluble. Calcium phosphate compounds were the dominant fraction (≤?68%) of the soluble inorganic soil P followed by occluded iron phosphate (≤?48%), and all other fractions were ≤?9%. Isotopic measurements showed that ≈?50% of fertilizer P was non–exchangeable within 2 days, and TSP values in each fraction of soil inorganic P fluctuated in relatively similar proportions to the concentrations of P fractions in soil. Available P (soil & TSP) in cropped soil was more than that in the uncropped soil, and plants had no effect on the distribution of P from fertilizer amongst the different soil P fractions.     

蚯蚓对土壤中铜、镉生物有效性的影响

以第四纪红黏土红壤和长江冲积物形成的高砂土为供试土壤、分别加入3个浓度的Cu^2 (100、200、400mg／kg)或Cd^2-(5.10、20mg/kg)模拟土壤污染．设置接种蚯蚓(Pheretima sp.)处理与不加蚯蚓对照．并种植黑麦草(Lolium multiflorum)、研究蚯蚓活动对土壤中Cu、Cd生物有效性的影响．以揭示蚯蚓在植物修复重金属污染土壤中的作用。结果表明：蚯蚓活动显著增加红黏中DTPA提取态Cu的含量、只有在浓度低于200mg／kgCu的处理中．才能增加CaCl2提取态Cu的含量．对H2O提取态Cu影响甚微;而对高砂土上Cu、Cd的各种形态影响均不显著;除红黏中浓度高于100mg／kgCu和10mg／kgCd处理外．蚯蚓活动显著提高了两种土壤上黑麦草地上部的生物量;接种蚯蚓后各种重金属处理中黑麦草对Cu的吸收量也显著增加,而Cd的吸收量变化不大。蚯蚓可能通过提高重金属的生物有效性而间接影响植物对重金属的修复效率。     

Plant availability of applied and native boron in soils with diverse properties

Laboratory and greenhouse research was conducted to study effects of soil properties on the availability of native and applied B in 14 Virginia soils. Boron absorption could be described by the Langmuir equation in 12 of the 14 soils, and maximum B adsorption (Vmax) in these 12 soils ranged from 3.3 to 26.5 mg kg⁻¹. A multiple regression equation, −19.3+3.51 pH+0.048 clay content, accounted for 89.6% of the variation in Vmax for the 12 soils. Curvilinear relationships (α=0.01) occurred between B in corn (Zea mays L.) tissue from native B and hot-water soluble B, mannitol exchangeable B, and NH₄-acetate and Mehlich III extractable B. Among these four procedures, mannitol exchangeable B correlated most closely (r=0.923) with B in corn tissue from native B. From 0.4 to 13.5% of the applied B was absorbed by corn plants and translocated to shoots. Curvilinear relationships (α=0.01) occurred between B in corn tissue from applied B and soil clay content, NH₄-oxalate extractable Al and Fe, and acidified NH₂OH·HCl extractable Mn. It is evident from these relationships that soil clay and oxyhydroxides of Al, Fe, and Mn have an affinity to adsorb B in somewhat unavailable forms.     

Biotechnological strategies applied to the decontamination of soils polluted with heavy metals

Soils have been submitted to several contaminants that vary in concentration and composition. Heavy metals can be widely spread and accumulated in those environments due to some inappropriate actions. In this present review some remediation techniques to remediate soils are presented, focusing on the use of plants that are capable of surviving in soils with heavy metals along with the function of some microorganisms in the restoration process.     

热带亚热带常绿阔叶林维持酸性土壤有效磷水平的磷转化过程

热带和亚热带酸性土壤磷矿物的沉淀通常被认为会限制土壤有效磷的供应.选择以西双版纳山地季风常绿阔叶林和哀牢山中山湿性常绿阔叶林为代表的热带亚热带酸性土壤,探讨两类森林维持土壤有效磷水平的磷转化过程.哀牢山中山湿性常绿阔叶林腐殖质厚、而西双版纳山地季风常绿阔叶林的腐殖质几乎不存在.两地均显示土壤有效磷库随着土壤有机质含量的减少而降低.有机质含量较低的西双版纳表层矿质土（0～10 cm）的微生物生物量磷库大于有机质含量相对较高的哀牢山表层矿质土的微生物生物量磷库,且微生物对磷的固定占有效磷来源（磷矿物的溶解和有机磷的矿化）的比例为74%,高于哀牢山表层矿质土的63%.哀牢山表层矿质土的土壤有效磷库大于西双版纳,其土壤有效磷库可能更多的依赖于覆盖于其上的腐殖质分解后向下的磷输入.与两地的矿质土相比,哀牢山腐殖质具有高的磷净溶解率、总有机磷矿化速率和磷微生物固定速率.结果表明,热带山地季风常绿阔叶林主要通过微生物固定来避免土壤磷矿物的沉淀和保持土壤磷的有效供应;而亚热带中山湿性常绿阔叶林除具有较高的微生物固定外,地表腐殖质层的存在也帮助避免土壤磷矿物的沉淀而保持土壤有效磷的供应.