水稻幼苗镉积累特征和离体叶片耐镉性的基因型差异

水稻根系对镉(Cd)的富集能力和向地上部的转运效率直接决定着水稻地上部的Cd积累量,是影响稻米中镉含量的关键因素。提高水稻根系对Cd的阻控能力有助于降低南方稻区大米镉含量超标的风险。以水稻核心种质资源中的高Cd积累品种‘齐头白谷’和低Cd积累品种‘27760’的幼苗和离体叶片为材料,对其Cd吸收转运特性和耐镉能力进行了比较研究。结果表明,根系细胞壁和原生质体的Cd吸收动力学特征都符合米氏方程,‘齐头白谷’的Cd最大吸收速率F_(max)显著大于‘27760’,Km值无显著差异。当根际环境中的Cd浓度高于0.89μmol·L~(-1)时,‘齐头白谷’的细胞壁和原生质体的Cd积累速率显著高于‘27760’。地上部细胞壁和原生质体的Cd吸收速率与根系可溶性组分中的Cd浓度呈显著的线性正相关。当根系可溶性组分中的Cd浓度相近时,‘齐头白谷’地上部细胞壁和原生质体的Cd积累速率显著高于‘27760’。在0.89~8.9μmol·L~(-1)的Cd溶液中,‘齐头白谷’离体叶片的失绿速度明显低于‘27760’。‘齐头白谷’具有耐Cd能力强、Cd积累速率快和转运效率高的特点。水稻离体叶片的耐Cd能力和幼苗根系的Cd积累能力以及幼苗的Cd转运能力高度相关,它们都可作为快速鉴定低Cd积累品种的生理指标。     

薄膜扩散梯度技术测量砷的影响因素及其应用

研究了水体中常见无机阴离子和腐植酸对以氧化锆为固定膜的新型薄膜扩散梯度技术(Zr-oxide DGT)测量砷(As)的影响及其在自然地表水体中的应用.结果表明,短期(16h)暴露,SO₄^2-无影响,而HCO₃^-、Cl^-、SiO₃^2-和腐植酸有一定的影响,其忍耐的最高浓度值分别为360mg/L、45g/L、100mg/L和36mg/L.1~4d暴露期间,37~148mg/L的HCO₃^-、1.44~2.88g/L的SO₄^2-、12~24g/L 的Cl^-、8~24mg/L的SiO₃^2-和3~9mg/L的腐植酸均无影响,而高浓度的HCO₃^-(370mg/L)、SO₄^2- (8.64g/L)、Cl^-(72g/L)和腐植酸(27mg/L) 3~4d以及SiO₃^2-(72mg/L) 2~4d的存在明显降低该技术对As的吸收富集,并对As(III)的作用更大.将Zr-oxide DGT技术应用于南京市地表水体,并与传统的主动监测方法进行比较,发现利用Zr-oxide DGT技术测得的溶解态As浓度与传统的主动采样技术测定浓度一致.     

环境浓度水平的镍对不同生命阶段秀丽线虫(Cae-norhabditis elegans)体长与运动的刺激效应

毒物兴奋效应(hormesis)受到广泛关注。本文以秀丽线虫(Caenorhabditis elegans)的L1(自虫卵开始培养10 h)、L3阶段(36 h)和年轻成虫阶段(72 h)为起始暴露阶段,进行环境浓度(3.18E-3、3.18E-2、3.18E-1和3.18μmol·L-1)水平的72 h镍暴露试验,以体长与行为学指标为终点研究了不同生命阶段对毒物兴奋效应的影响。在所有暴露浓度下,镍对L1线虫的体长均表现出显著的刺激效应,3个较高浓度下(3.18E-2、3.18E-1和3.18μmol·L-1)的刺激效应相似,均表现为比空白多23.6%(P0.05)的水平;L3线虫的体长在低浓度受到刺激,在高浓度受到抑制,表现为毒物兴奋效应;年轻成虫在所设4个浓度下均没有显著响应。在所有暴露浓度下,镍对L1线虫的身体弯曲运动无显著效应;镍对L3线虫的身体弯曲频率表现为刺激效应,并且该刺激效应随暴露浓度增加,先增加后减小,在3.18E-2μmol·L-1表现出最大刺激效应,比空白多59.0%(P0.05);镍对年轻成虫的身体弯曲频率表现为比空白多17.7%~30.1%(P0.05)的刺激效应,该刺激效应在不同浓度下不具有显著性差异。镍对L1线虫的倒退运动表现出显著的、随暴露浓度增加而增加的刺激效应,在3.18μmol·L-1表现出最大刺激效应,比空白多187.0%(P0.05);镍对L3线虫的倒退运动在3.18μmol·L-1下表现为比空白多22.7%(P0.05)的刺激效应;镍对年轻成虫的倒退运动在较高的3个浓度下(3.18E-2、3.18E-1和3.18μmol·L-1)表现为比空白多46.7%~86.7%(P0.05)的刺激效应。研究揭示环境浓度水平的镍暴露对不同生命阶段秀丽线虫的体长与运动具有不同程度的刺激效应。     

Levels and distribution of trace metals in surface sediments from Kongsfjorden, Svalbard, Norwegian Arctic

Trace metal contents (Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb and Zn) have been measured in 27 surface sediment samples collected from Kongsfjorden, Svalbard, Norwegian Arctic. The analyses yielded concentration values (in mg kg^?1) of 0.13–0.63 for Cd, 11.89–21.90 for Co, 48.65–81.84 for Cr, 21.26–36.60 for Cu, 299.59–683.48 for Mn, 22.43–35.39 for Ni, 10.68–36.59 for Pb, 50.28–199.07 for Zn and 8.09–65.34 for Hg (in ng g^?1), respectively. Relative cumulative frequency method has been used to define the baseline values of these metals, which (in mg kg^?1) were 0.14 for Cd, 13.56 for Co, 57.86 for Cr, 25.14 for Cu, 364.08 for Mn, 26.22 for Ni, 17.46 for Pb, 70.49 for Zn and 9.76 for Hg (in ng g^?1), respectively. The enrichment factor analysis indicated that Hg showed some extent of anthropogenic pollution, while Pb, Zn and Cd showed limited anthropogenic contamination in the study areas.     

Interrelation of Cd‐lon concentrations and the growth and activities of microorganisms in two growth media†

Partitioning of native or anthropogenic heavy metals in solid and solution phases of soil is a result of network of several physico‐chemical reactions. The attainment of equilibrium between two phases is also regulated by biochemical processes. For practical purposes, the bioavailability of metal present in soil is predominantly regulated by the soil solution phase which is in dynamic equilibrium with the solid phase. The results of a model laboratory and greenhouse growth experiments have been used to investigate the effect of Cd‐ion concentrations (either in soil solution or in nutrient solution) on the growth and activities of microorganisms. The soil solution has been simulated by preparing a suspension of soil with 0.1 M NaNO₃ (1: 2.5) equilibrated for two hours. Important conclusions are as follows:

Increase in Cd‐ion concentration in soil solution or in nutrient solution induces corresponding adverse effect on the growth and activities of microorganisms. Thus, it seems that Cd‐ion concentration is a more sensitive indicator for assessing the effect of metal pollution upon the growth and activities of soil microorganisms in comparison to total Cd contents.

During active microbial growth phase, a large part of the organically bound Cd was released in the soil solution which is largely bioavailable. This process is termed as mobilisation. There was momentary increase of Cd‐ion concentration in soil solution which intoxicated the growing organisms. After this stage, the Cd ions from the solution phase were removed by the newly formed solid phase (nonviable biomass) and were transformed in non‐available form. This process is termed as immobilisation.

The consequences and importance of these results for practical agriculture and in deciding the limits or guidelines on the maximum tolerable metal load in soils are discussed.     

Denitrification in bottom sediment near oil production facilities off the Louisiana Gulf Coast

There is little information on denitrification in Gulf of Mexico bottom sediment. Potential denitrification rates in surface sediment were measured along transects legs extending 0–800 m from two offshore oil production platforms. The average potential denitrification ranged from approximately 50 mg N m^?2 d^?1 in surface sediment near the platforms to 15 mg N m^?2 d^?1 in sediment 800 m from the platforms. Measured denitrification rates were correlated to a higher organic matter content in sediment nearer the platforms. This research examined only a small component of nitrogen processing in Gulf of Mexico sediment. Additional research should examine the effect of nitrogen loading and temporal and spatial variability on denitrification rate.     

Ecological planning for promoting urban sustainable development: A case study of Shenzhen Special Economic Zone,China

Based on the case study of Shenzhen Special Economic Zone, China, this paper investigates the theories and application of ecological planning for promoting urban sustainable development. The stated significance of such development is to promote the co-ordination of relationships between man and nature, and man and the environment.     

Ecological properties of soil water and effects on forest vegetation in the Loess Plateau

In the Loess Plateau of China, soil water has three ecological properties: high infiltration capacity, high storage capacity and availability to deep plant roots. Soil desiccation is the most serious problem for forest vegetation in the Loess Plateau. Arid soils are the result of intensified soil desiccation caused by disturbances in plant succession, which constitute the ecological foundation of soil water. The negative effects of the arid soil layer on surface water infiltration for recharging underground water are discussed in terms of ecological hydrology. The arid soil layer disrupts the link between surface water and underground water and prevents vertical precipitation infiltration from supplementing underground water. Forest vegetation has a significant runoff-retaining efficiency that reduces total runoff from forest areas leading to low surface and ground runoff which affect the water cycle on a watershed scale.     

There are many ways to be a mutualist: endophytic fungus reduces plant survival but increases population growth

One of the challenges to quantifying the costs and benefits of symbiosis is that symbionts can influence different components of host fitness. To improve understanding of the ecology of inherited symbionts, we developed general theory for a perennial host-hereditary symbiont interaction, in which symbionts can have independent and potentially opposing effects on host regeneration and survival. The model showed that negative effects on one component of fitness may be outweighed by positive effects on another, leading to a net positive impact of symbiosis on population growth. Model predictions depended on the availability of suitable patches, which influenced the relative contributions of survival vs. regeneration to host fitness. We then used experimental symbiont removal to quantify effects of a hereditary, fungal endophyte on a grass host. Endophyte presence strongly reduced host survival but increased regeneration. Application of the model revealed that negative effects on plant survival were overwhelmed by beneficial effects on regeneration, resulting in stable endophyte persistence at 100% frequency, consistent with field observations. Our work demonstrates the utility of a demographic perspective for predicting the dynamics of symbioses and supports the hypothesis that symbionts function as mutualists when host and symbiont fitness are coupled through vertical transmission.