Is The Ca + K + Mg/Al Ratio in the Soil Solution a Predictive Tool for Estimating Forest Damage?

The ratio between (Ca +K +Mg) and Al in nutrientsolution has been suggested as a predictive tool forestimating tree growth disturbance. However, the ratiois unspecific in the sense that it is based on severalelements which are all essential for plant growth;each of these may be growth-limiting. Furthermore,aluminium retards growth at higher concentrations. Itis therefore difficult to give causal and objectivebiological explanations for possible growthdisturbances. The importance of the proportion ofbase-cations to N, at a fixed base-cation/Al ratio, isevaluated with regard to growth of Picea abies.The uptake of elements was found to be selective;nutrients were taken up while most Al remained insolution. Biomass partitioning to the roots increasedafter aluminium addition with low proportions of basecations to nitrogen. We conclude that the low growthrates depend on nutrient limitation in thesetreatments. Low growth rates in the high proportionexperiments may be explained by high internal Alconcentrations. The results strongly suggest thatgrowth rate is not correlated with the ratio in therooting medium and question the validity of usingratios as predictive tools for estimating forestdamage. We suggest that growth limitation of Picea abies in the field may depend on lowproportions of base cations to nitrate. It istherefore important to know the nutritional status ofthe plant material in relation to the growth potentialand environmental limitation to be able to predict andestimate forest damage.     

凋落物覆盖及掩埋对不同质量的藜蒴种子萌发和幼苗生长的影响

以南亚热带常见的先锋乡土树种藜蒴(Castanopsis fissa)为研究对象.通过室内萌发试验,分析了种子质量、凋落物覆盖和掩埋对种子萌发及幼苗早期生长的影响.结果表明,藜蒴种子能否成功萌发并形成幼苗的决定性因素是种子的掩埋深度.掩埋显著抑制了藜蒴种子萌发及形成幼苗的过程,随掩埋深度的增大,这种抑制作用越明显.掩埋对幼苗的存活和生物量没有显著影响,但可提高幼苗根部生物量的分配.深度掩埋时,质量大的种子在幼苗形成过程中具明显优势;而置于土壤表层或浅埋的种子成苗率与种子质量的相关性较低.大质量种子形成的幼苗更易于存活,在生物量的积累方面也表现H{一定的优势.凋落物覆盖未抑制幼苗的出土,且对幼苗的存活和生长具有明显的促进作用,表现在可提高幼苗的相对生长率以及生物量的积累.另外,凋落物的覆盖明显提高了幼苗生物量在其冠部的分配.因而,若利用直接播撒藜蒴种子的方式改造南亚热带退化草坡.理论上应尽可能选用大质量的种子直接播种于地表,并覆以原有的地表凋落物,以促进藜蒴幼苗成功建立.     

模拟氮沉降对大豆萌发和幼苗生长的影响

氮沉降是当今倍受关注的全球性环境问题.采用大田试验和室内培养的方法,研究大豆种子萌发和幼苗生长对氮沉降的响应.实验设4组处理(CK、T1、T2、T3),所施氮肥为NH4NO3,在室内培养实验中,4组处理的浓度分别为0、0.08、0.16、0.24mol/L.大田实验中,4组处理的氮施入量分别为0,50,100,150 kg·hm-2·a-1.结果表明:过量氮沉降对种子萌发有一定的抑制作用,降低了种子的发芽速度和发芽率;抑制了幼苗的生长速度,降低了植株的株高、叶面积和生物量,并减小了根冠比;随着氮施入量的增加幼苗的蒸腾速率逐渐降低,但叶片叶绿素含量逐渐增加.     

云南粳稻核心种质杂种后代孕穗期耐冷性研究

以236份云南地方粳稻核心种质和云南主栽梗稻Oryza satica品种合系35配制的杂种F5、BC1F4、BC2F3和BC3F2为材料,在昆明自然低温平均17.8℃(冷害)条件下,对亲本及其后代进行孕穗期耐冷性研究.结果表明:①亲本耐冷性状间的相关性明显高于其杂种后代,不同世代间总体趋势为随着回交世代增加其性状间相关性减弱.在亲本及其杂种后代间耐冷指标性状穗颈长、穗下节长、每穗实粒数、每穗秕粒数与结实率均呈较高的(≥0.370)极显著(n=236,R0.01=0.181)相关.②株高、穗颈长、穗下节长等耐冷性状在亲本强弱耐冷系统群间的差异明显,表现为亲本耐冷性强的材料秆和穗较长、穗粒数较多,同一性状变异程度减小.但随着回交代数的增加,这些性状的平均值逐渐趋同于轮回亲本,差异减小.③穗颈长、穗下节长、每穗实粒数、每穗秕粒数与结实率在5个稻作区间的变化规律呈现一致性,亲本和F5的差异较大,而BC2F4、BC2F3和BC3F2的差异较小,且趋同于轮回亲本.通过连续回交,在BC3F1即可获得耐冷性状表现良好的材料.     

Types of Ectomycorrhiza as Pollution Stress Indicators: Case Studies in Slovenia

Mycorrhiza is the main spatial and temporal linkage between different constituents in a forest ecosystem. The functional compatibility and stress tolerance of ectomycorrhizal types is species specific, and therefore the information on the ectomycorrhizal community structure can add to the understanding of processes in forest ecosystems and can also be applied as tools for bioindication of pollution stress in forest soils. We have studied the effects of pollution (N and S) on trees and forest soils by: (1) quantification of ECM types diversity as in situ indicators in forest stands, (2) determination and quantification of pollution-sensitive or -insensitive ECM types as passive monitors, (3) root growth and development of ECM on nonmycorrhizal spruce seedlings, planted at the studied sites (active monitors), and (4) ECM infection (a bioassay based on mycorrhizal inoculum potential) of seedlings in an experimental set-up as ex situ testers. ECM species richness for Norway spruce trees (Picea abies) showed higher values in unpolluted sites than in polluted ones, while the differences were not significant for European beech trees (Fagus sylvatica). As pollution-sensitive or -insensitive ECM species in spruce forests, we suggest Hydnum rufescens (sensitive) and Paxillus involutus (unsensitive). Mycorrhizal potential in Norway spruce seedlings as a bioassay for soil N and S pollution was effective, and is suggested as an additional, standardized and widely comparable system in bioindication of soil pollution.     

Types of Ectomycorrhiza of Mature Beech and Spruce at Ozone-Fumigated and Control Forest Plots

In the Kranzberg forest near Freising (Germany) a novel “Free-Air Canopy O₃ Exposure” system has been employed for analysing O₃-induced responses from sub-cellular to ecosystem levels that are relevant for carbon balance and CO₂ demand of 60-year-old beech trees. The below-ground ectomycorrhizal community was studied in two-fold ambient O₃ concentrations (five cores per sampling) and in a control plot with an ambient O₃ concentration (four cores per sampling). Five samplings were taken throughout two vegetation seasons (2003 and 2004). Types of ectomycorrhiza were determined by their morphological, anatomical and molecular characteristics and quantified by counting. The total number of mycorrhizal fine roots was higher at the fumigated plot as compared with the control site. The numbers of ectomycorrhizal types at the fumigated and control plots were 28 and 26, respectively. Cenococcum geophilum was present in all soil cores at all sampling times with a significant increase in abundance under ozone-fumigated trees. Other mycorrhizal types present at higher abundance at the fumigated than at the control plot were identified as Russula densiflora, R. fellea, R. illota, Tuber puberulum, Lactarius sp. 2 and Russula sp. 2. Some mycorrhizal types were present exclusively at the fumigated plot (Fagirhiza fusca, F. setifera, Lactarius acris, Piceirhiza nigra and Russula sp. 1). A possible ecological role for the abundant types of ectomycorrhiza and their putative application in bio-indication is discussed.     

水稻专用叶面喷剂对水稻幼苗生长的影响

用水稻专用叶面喷剂喷施水稻秧苗,1670~2500mg/L浓度处理可改善秧苗素质,控制株高,秧苗粗壮,假茎宽,干物质增多,促进分蘖．5000mg/L浓度处理抑制秧苗生长．水稻专用叶面喷剂可提高秧苗叶片可溶性糖、可溶性蛋白质、叶绿素含量和硝酸还原酶活性．     

Modulation of steroidogenesis by coastal waters and sewage effluents of Hong Kong, China, using the H295R assay

BACKGROUND, AIM, AND SCOPE: The presence of a variety of pollutants in the aquatic environment that can potentially interfere with the production of sex steroid hormones in wildlife and humans has been of increasing concern. The aim of the present study was to investigate the effects of extracts from Hong Kong marine waters, and influents and effluents from wastewater treatment plants on steroidogenesis using the H295R cell bioassay. After exposing H295R cells to extracts of water, the expression of four steroidogenic genes and the production of three steroid hormones were measured. MATERIALS AND METHODS: Water samples were collected during the summer of 2005 from 24 coastal marine areas and from the influents and effluents of two major waste water treatment plants (WWTPs) in Hong Kong, China. Samples were extracted by solid phase extraction (SPE). H295R cells were exposed for 48 h to dilutions of these extracts. Modulations of the expression of the steroidogenic genes CYP19, CYP17, 3betaHSD2, and CYP11beta2 were determined by measuring mRNA concentrations by real-time polymerase chain reaction (Q-RT-PCR). Production of the hormones progesterone (P), estradiol (E2), and testosterone (T) was quantified using enzyme linked immunosorbent assays (ELISA). RESULTS: Extracts from samples collected in two fish culture areas inhibited growth and proliferation of H295R cells at concentrations greater or equal to 10(5) L equivalents. The cells were exposed to the equivalent concentration of active substances in 10,000 L of water. Thus, to observe the same level of effect as observed in vitro on aquatic organisms would require a bioaccumulation factor of this same magnitude. None of the other 22 marine samples affected growth of the cells at any dilution tested. Twelve of the marine water samples completely inhibited the expression of CYP19 without affecting E2 production; inhibition of CYP17 expression was observed only in one of the samples while expression of CYP11beta2 was induced as much as five- and ninefold after exposure of cells to extracts from two locations. The expression of the progesterone gene 3betaHSD2 was not affected by any of the samples; only one sample induced approximately fourfold the production of E2. Although more than twofold inductions were observed for P and T production, none of these values were statistically significant to conclude effects on the production of these two hormones. While influents from WWTPs did not affect gene expression, an approximately 30% inhibition in the production of E2 and a 40% increase in P occurred for the exposure with influents from the Sha Tin and Stonecutters WWTPs, respectively. Effluents from WWTPs did not affect the production of any of the studied hormones, but a decrement in the expression of the aldosterone gene CYP11beta2 was observed for the Sha Tin WWTP exposure. No direct correlation could be established between gene expression and hormone production. DISCUSSION: Observed cytotoxicity in the two samples from fish culture areas suggest the presence of toxic compounds; chemical analysis is required for their full identification. Although effluents from WWTPs did not affect hormone production, other types of endocrine activity such as receptor-mediated effects cannot be ruled out. Interactions due to the complexity of the samples and alternative steroidogenic pathways might explain the lack of correlation between gene expression and hormone production results. CONCLUSIONS: Changes observed in gene expression and hormone production suggest the presence in Hong Kong coastal waters of pollutants with endocrine disruption potential and others of significant toxic effects. The aromatase and aldosterone genes seem to be the most affected by the exposures, while E2 and P are the hormones with more significant changes observed. Results also suggest effectiveness in the removing of compounds with endocrine activity by the WWTPs studied, as effluent samples did not significantly affect hormone production. The H295R cell showed to be a valuable toll in the battery required for the analysis of endocrine disrupting activities of complex environmental samples. RECOMMENDATIONS AND PERSPECTIVES: Due to the intrinsic complexity of environmental samples, a combination of analytical tools is required to realistically assess environmental conditions, especially in aquatic systems. In the evaluation of endocrine disrupting activities, the H295R cell bioassay should be used in combination with other genomic, biological, chemical, and hydrological tests to establish viable modes for endocrine disruption and identify compounds responsible for the observed effects.     

毒死蜱生态毒理与风险研究综述

毒死蜱被认为是一种高效、安全和广谱的含氮杂环类杀虫杀螨剂,被广泛应用于农业生产病虫害的防治中。在中国,毒死蜱曾被列为取代高毒农药的重要品种,并被农业部推荐用于无公害农产品生产的专用杀虫杀螨剂。近年来,由于不断发现的毒死蜱生物毒性及其产生的环境安全问题,美国和欧盟国家已经在某些范围内禁用毒死蜱。综合近几年文献,从环境介质含量、转化行为、生物活性检测以及国外水质基准等方面,对其分别叙述,旨在为今后中国地区毒死蜱的环境健康风险评价、生态风险评价和水质基准制定提供基本参考依据。     

外源NO对NaCl胁迫下黄瓜幼苗生长和根系膜脂过氧化作用的影响

采用营养液水培,研究外源NO对NaCl胁迫下黄瓜幼苗生长、根系膜脂过氧化作用的影响.结果表明,100 μmol·L-1NO供体硝普钠(SNP)能显著缓解50 mmol·L-1NaCl胁迫对黄瓜植株造成的伤害,提高幼苗生长量,增强幼苗根系抗氧化酶活性,提高根系脯氨酸(Pro)含量,缓解根系膜脂过氧化作用,从而提高植株耐盐性.