基于物种敏感性分布（Burr-Ⅲ）模型预测Cd对水稻毒害的生态风险阈值HC5

Burr-Ⅲ型分布是一种灵活的分布函数模型,对有害物质产生毒性的物种敏感性数据有很好的拟合效果。本研究采用水培实验研究了我国常见的17种不同水稻对Cd毒性的剂量-效应关系,结合Burr—Ⅲ物种敏感性分布模型对不同水稻Cd毒性的物种敏感性分布频次和基于保护95％水稻品种的Cd毒性阈值HC5进行了预测。结果表明：水培条件下,随着Cd处理浓度（0．30 - 6．0mg·L^-1）的增加,水稻对Cd富集系数（SCV）明显下降,而转运系数（TF）呈现出增加的趋势,总体而言,杂交品种水稻对Cd的转运系数高于常规品种水稻。不同水稻对Cd胁迫的半抑制浓度阈值（EC50）变化范围为0．552—24．01mg·L^-1,不同水稻品种EC50相差1．18-43．49倍,10％抑制浓度（EC10）变化范围为0．033～1．624mg·L^-1,不同水稻品种EC50相差1．758-49．21倍。不同水稻对Cd的毒性呈现出明显的敏感性差异特征,Bur-Ⅲ分布模型预测结果表明,基于保护95％的水稻品种,Cd的10％抑制浓度值（HC5^10%）为0．045mg·L^-1,50％抑制浓度值（HC550％）为0．594mg·L^-1。研究结果为我国水稻Cd污染防治及土壤Cd质量标准的修订提供了依据。     

Changes in Anthocyanin Content as Indicator of Maize Sensitivity to Selenium

The aim of this experiment was to examine the effect of exogenous selenium (Se) on anthocyanin and chlorophyll accumulation, Se content, as well as the growth of maize (Zea mays var. ‘saccharata Kcke’) cv. ‘Zlota Karlowa’ seedlings. Plants were grown hydroponically in Hoagland's nutrient solution at different pH values: 4.5, 6.2, and 7.5. Selenium was added to the solution as either selenate (Na₂SeO₄) or selenomethionine (C₅H₁₁NO₂Se) to a final concentration of: 0 (control), 5, 25, 50, and 100 μ M Se. Generally, the presence of Se in the medium caused an increase in the anthocyanin content and a simultaneous decrease of the total chlorophyll concentration depending on the Se form and dosage. Higher concentrations of anthocyanin were detected in the presence of selenomethionine than selenate, notably at pH 4.5. The effect of individual Se forms on maize seedlings, expressed on the basis of the fresh weight, indicate that selenomethionine was more phytotoxic than selenate. Selenium content both in roots and shoots increased linearly with increasing Se concentration in solution culture. However, a much higher Se level was found in the maize organs when plants were supplied with selenomethionine than selenate. Experimental evidence shows that the changes in anthocyanin content can be used as a test parameter reflecting the degree of Se toxicity in maize plants, and may be potential useful for bioindication of Se phytotoxicity in other higher plants.     

Effects of pH and selenium oxidation state on the selenium accumulation and yield of alfalfa

Experiments were performed in greenhouse sand culture to determine the effect of pH and Se oxidation state on the tissue composition and yield of alfalfa (Medicago sativa L.). Alfalfa was planted and irrigated with nutrient solution containing 0, 0.25, 0.5, 1.0 or 3.0 mg Se L^‐1 as Na₂SeO₃ or Na₂SeO_l4. The solution pH was maintained at 7.0 ± 0.2 or 4.5±0.2. Three harvests were made and the shoots and roots weighed and analyzed for total Se. At the levels tested, additions of Se to the treatment solutions increased the tissue Se concentrations and depressed alfalfa shoot growth regardless of Se oxidation state or pH. Root growth was reduced in the presence of Se(VI) but was unaffected by Se(IV). Selenium was accumulated to higher concentrations in the shoot when supplied as Se(VI) compared to Se(IV) and accumulated to higher concentrations in the root when added as Se(IV) compared to Se(VI). Relative shoot yields were depressed more by Se(IV) then Se(VI) at pH 7, but there was no difference between Se(IV) and Se(VI) at pH 4.5. Relative root yields were depressed by Se(VI) but not by Se(IV).     

Interactive effects of sodium chloride,sodium sulfate,calcium sulfate,and calcium chloride on snapbean growth,photosynthesis, and ion uptake

Excessive sodium (Na) accumulation in soil, which can be a problem for production agriculture in arid and semiarid regions, may be ameliorated by calcium (Ca). The mechanisms of Ca amelioration of Na stress in plants have received much more attention than has the effect of the anion of the Ca salt. Our objective was to determine the relative effects of the chloride (Cl^‐) and sulfate (SO₄ ^2‐) anions on Ca amelioration of Na stress. We exposed Phaseolus vulgaris L., cv. Contender seedlings growing in 1‐L styrofoam pots under greenhouse conditions to sodum chloride (NaCl) or sodium sulfate (Na₂SO₄) at concentrations of 0, 15, 30, 45, and 60 mmol/L combined with either 15 and 30 mmol/L of calcium sulfate (CaSO₄) or calcium chloride (CaCl₂). Plants in each styrofoam pot were irrigated with 300 mL of salt solution (leaching fraction = 0.25) every fourth day for four weeks. Increasing Na concentration decreased shoot dry weight, number and weight of pods, and number of nodules. The photo‐ synthesis rate was affected by all levels and types of Na salts. Calcium sulfate treatments ameliorated Na‐induced salinity in snapbeans more than did comparable CaCl₂ treatments. The thermodynamic activity of Ca, Na, and Cl was linearly related to the tissue content of each ion.     

不同性质土壤中钼的植物毒性及预测模型

以我国9个地区不同理化性质的土壤为研究对象,通过外源添加钼酸盐（Mo⁶⁺）评估了土壤Mo对大麦（Hordeum vulgare L.）的毒性,在此基础上分析了土壤性质因子和毒性阈值之间的相关性,并建立了一元和多元线性回归方程。结果表明,在9个地区的土壤中,Mo对大麦根伸长10%抑制率（EC₁₀）和50%抑制率（EC₅₀）的变化范围分别为262.64~3 301.70 mg·kg^-1和851.10~5142.62 mg·kg^-1;土壤阳离子交换量（CEC）是影响土壤Mo毒性阈值最重要的因子;基于CEC建立的回归方程中引入pH值和锰氧化物含量时,预测能力显著提升,可以分别解释EC₁₀和EC₅₀的82.2%和88.5%的变异（P<0.05）。利用欧洲9个地区土壤的大麦毒性数据对模型进行验证,发现基于我国土壤建立的Mo毒性预测模型并不适用于欧洲土壤,进一步分析了我国和欧洲18个地区的土壤性质和毒性阈值的相关性并建立了预测模型。研究表明,CEC对Mo的大麦毒性有显著影响,基于CEC、pH值和锰氧化物含量建立的预测模型可以准确评估我国和欧洲18个地区土壤Mo的毒性。本研究可为土壤Mo的风险评价和修复提供重要参考。     

Alleviation effects of calcium and potassium on cadmium rhizotoxicity and absorption by soybean and wheat roots

The objectives of the present study were to investigate the root responses of soybean (Glycine max L.) and wheat (Triticum aestivum L.) seedlings to cadmium (Cd) stress and to investigate the alleviation effects of Ca and K on rhizotoxicity and absorption of Cd by roots. Soybean and wheat seedlings in a hydroponic system were exposed to Cd‐spiked solutions (0, 4, 8, 12, and 16 μM) with different Ca (0.5, 1, and 10 mM) and K (0.3, 1.2, and 9.6 mM) levels for 7 d. The results showed a dramatic reduction in root elongation of soybean due to increased Cd, but increasing Ca and K levels alleviated this reduction in soybean. The amelioration of Cd toxicity by the addition of Ca may be associated with reduced Cd absorption. However, the addition of K in reducing Cd toxicity might not be dependent upon Cd absorption. Compared with soybean, wheat showed a relatively high tolerance to Cd. The alleviation of Cd rhizotoxicity in wheat was more apparent by K than by Ca. We found that the addition of K promoted root elongation but not directly prevent Cd stress, and that the addition of Ca minimized acute rhizotoxicity of Cd in wheat. Moreover, the addition of Ca reduced Cd absorption by soybean and wheat roots. However, the addition of K only reduced Cd absorption by wheat roots.     

Promoting Forest Recovery on a Surface Mine Site With Nutritional Amendments

Selected nutrient amendments were evaluated for their capacity to enhance growth and nutrition of Jeffrey pine (Pinus jeffreyi Grev. & Balf.) seedlings 3 yr after planting on an acidic Sierra Nevada surface mine. The amendments were applied by topdressing at four rates each and consisted of Forestcote 22-4-6 + Minors, a controlled release formulation; Free Flow 29-3-4 and Hydro Agri 21-7-14, two conventional fertilizers with the former featuring urea as the predominant N source while that for the latter was exclusively ammoniacal and nitrate forms; and Milorganite 6-2-0 + Iron, an organic amendment derived from municipal biosolids. The Forestcote and Free Flow formulations proved most adept at reinvigorating seedling growth while Hydro Agri and Milorganite were the least stimulatory. The lowest application rates employed were inadequate but the most advantageous rate differed somewhat by formulation. Foliar analysis revealed that fertilized seedlings had more N and P but less Mn and Al than the control. Enhanced N nutrition especially, but also that of P, probably accounted for most of the growth stimulation by the amendments, as availability of both in the soil was limiting. Of the two metallic elements, reduced Mn was likely most critical because concentrations encountered here were exceedingly elevated overall, including that in the soil, although soil Al was high also. These results suggest that a variety of nutritional amendments can be employed in forest restoration on surface mine sites and those similarly degraded, including sites for which dry climates greatly influence the selection of remedial practices.     

Organic Amendment,Fertilizer, and Lime Effects on Bareroot Jeffrey Pine Outplanted on a Sierra Nevada Surface Mine

Abstract

Composted organic matter, controlled release fertilizer, and dolomitic lime soil amendments were evaluated for their effectiveness in facilitating the reforestation of an acidic, semiarid Sierra Nevada surface mine with bareroot Jeffrey pine (Pinus jeffreyi Grev. & Balf.). Single application rates were used for the organic matter (2.0 L) and lime (28 g) amendments while low and high rates (8 g and 16 g, respectively) of the chemical fertilizer, High N 22-4-6 + Minors, were employed. All amendments were administered at outplanting using the minisite application method. The organic and lime amendments suppressed seedling survival, more so with the former than the latter, but this result did not extend to the High N fertilizer. Growth was also suppressed by the organic and lime amendments, although there was some evidence that these responses were waning late in the study, while High N was exceedingly stimulatory, especially with the high application rate. Annual assessment of seedling nutrition during this three-year study revealed numerous High N and organic matter treatment influences. Among them, increases in foliar N, P, and K and reductions in Fe, Mn, Zn, and Al were prominent within the High N treatments, but particularly so at the high application rate. For the organic matter treatment, the above increases and decreases in elemental concentrations were again noted, although the nutritional responses to this treatment were generally more subdued and somewhat ephemeral in comparison with those to High N. Calculation of base cation/metallic element molar ratios revealed that the organic matter treatment had the highest Ca/Al, Ca/Mn, Mg/Al, Mg/Mn, K/Al, K/Mn, and K/Cu during the initial season, but exerted little influence on these ratios thereafter. The High N treatments produced the highest Ca/Cu and Mg/Cu in the first season, the highest Ca/Al, Mg/Al, K/Al, and K/Mn in the second, and the highest Ca/Al, Mg/Al, Mg/Mn, K/Al, and K/Mn in the third season, with the high application rate especially prominent. Seedling nutrition was, at best, minimally affected by liming, with perhaps its most notable influence that of counteracting the positive responses indicated above with regard to the organic amendment effects on molar ratios. Overall, these results indicate that in the reforestation of difficult sites such as eastern Sierra Nevada surface mines, the favorable responses to controlled release fertilization can not be duplicated using composted organic amendments, and furthermore, dolomitic lime applications by the method used here are likely to prove exceedingly detrimental to seedling establishment.     

Effects of Tembotrione on Potato Crop in a Tropical Soil

ABSTRACT

Tembotrione is an herbicide with a high persistence in soil, a characteristic that affects the growth and development of susceptible cultures in succession. In this sense, the objective of this research was to evaluate the residual effects of tembotrione on production and quality of potato tubers in a tropical soil. A field experiment (2014/2015) with randomized blocks design with four replications was conducted. The treatments consisted of five doses of tembotrione (0, 8.4, 16.8, 33.6, and 50.4 g a.i. ha^?1) incorporated into the soil before planting the potato cultivar Atlantic. At 115 days after herbicide application were evaluated: total solids (%), dry matter content (DMCT %), nitrogen and potassium of the tubers, total yield and classification. The productivity of normal tubers decreased as doses of tembotrione were increased. The percentage of class I tubers was reduced at doses of 33.6 and 50.4 g a.i. ha^?1. The increase in the doses increased the percentage of class II tubers and did not influence the percentage of class III and discard. The appearance of cracked tubers increased with increasing herbicide doses. Tembotrione affected the productivity of potato tubers and caused cracks in the tubers, which are dependent on the applied doses.