Root uptake and distribution of radiocaesium from contaminated soils and the enhancement of Cs adsorption in the rhizosphere

Uptake by roots from contaminated soil is one of the key steps in the entry of radiocaesium into the food chain. We have measured the uptake by roots of radiocaesium and its transfer to shoots of a heathland grass, sheep fescue (Festuca ovina L.) from two contrasting agricultural soils, a sandy podzol and a clayey calcareous soil. A culture device which keeps the roots separate from the soil was used thus allowing rhizosphere soil to be obtained easily and enhancing the effect of root action. Biomass production and ¹³⁷Cs in shoots and roots were recorded. Cs adsorption was studied on both the initial, nonrhizosphere soil and on rhizosphere soil in dilute soil suspension. Cs desorption was measured by resuspending subsamples of contaminated soil in solutions containing various concentrations of stable Cs. The proportion of Cs fixed, i.e. not readily desorbable, was calculated by comparison of the adsorption and desorption isotherms. Uptake by roots varied considerably between soils and did not appear to be diffusion limited. Root-to-shoot transfer did not differ for the two soils studied. Root action considerably enhanced Cs adsorption on the soils, particularly the in sandy podzol with a low Cs affinity. The value of K_d was increased by up to an order of magnitude. A large proportion of adsorbed Cs was found to be fixed, the K_d was up to seven times greater on desorption than adsorption, indicating that up to 80% of adsorbed Cs was not readily exchangeable. Root action had little effect on the fixed fraction. This revised version was published online in June 2006 with corrections to the Cover Date.     

微生物菌剂对草坪植物高羊茅生长与土壤酶活性的影响

从生活垃圾堆肥中分离出放线菌、枯草芽孢杆菌和苏云金芽孢杆菌,通过形态学和染色鉴定,分别以微生物单菌剂施入到草坪土壤基质中,研究了几种微生物菌剂对高羊茅生长与土壤酶活性的影响。结果表明:3种微生物菌剂处理可以显著提高高羊茅株高、生物量和叶绿素含量(P0.01或P0.05),促进了高羊茅的生长。同时,施加不同的微生物菌剂对于土壤蔗糖酶、脲酶、过氧化氢酶、多酚氧化酶和过氧化物酶活性均有显著的增强作用,其中放线菌处理土壤脲酶和多酚氧化酶分别是对照的8.38倍和20.6倍。因此,从堆肥中得到的3种微生物菌剂均可有效提高土壤酶活性,改善植物根际微生态环境,提高了土壤肥力和养分的利用率,促进了草坪植物生长,改善草坪质量。该研究可为微生物菌剂在草坪建植体系中的应用提供依据。     

臭氧浓度升高对坪用高羊茅生长、亚细胞结构及活性氧代谢的影响

通过开顶箱(OTCs)模拟,以环境臭氧(O₃)浓度约40 nmol·mol^-1为对照,研究大气O₃浓度升高(80和160 nmol·mol^-1O₃)对冷季型草坪草高羊茅生长、亚细胞结构及其活性氧代谢的影响.结果表明: 14 d的80 nmol·mol^-1O₃熏蒸使高羊茅株高和叶宽降低,总生物量降低43.7%,老叶变黄,而160 nmol·mol^-1O₃处理高羊茅叶出现大量枯死褐斑,叶尖坏死,新叶卷曲,总生物量降低46.2%,叶肉细胞膜卷曲,叶绿体和线粒体受损严重.与对照相比,80和160 nmol·mol^-1O₃熏蒸下高羊茅叶片超氧阴离子(O₂^-·)产生速率、过氧化氢(H₂O₂)和丙二醛(MDA)含量显著增加,抗氧化酶活性显著升高,但叶片总酚含量和抗氧化能力随O₃浓度升高而先升高后降低.在明显O₃伤害症状出现之前,O₃已对高羊茅的生长和抗氧化代谢产生不利影响;高羊茅抗氧化系统虽对O₃浓度的升高存在一定的适应性反应,但其不能抵御过高浓度的长期胁迫和伤害.     

Lessons Learned about Research and Management: A Case Study from a Midwest Lowland Savanna,U.S.A.

Integrating research and practice is a fundamental challenge for restoration and conservation. Scientists recognize restoration as an opportunity to test basic ecological principles, and that core scientific practices such as establishing control plots, replication, monitoring, and data management are fundamental to learning from restoration and management. However, practical constraints inherent to many projects often work against fully integrating research and management. In 2005, we had the opportunity to evaluate a lowland savanna that had been undergoing restoration by The Nature Conservancy since 1997. We used the data generated as a case study to evaluate how the restoration process might have changed had scientists been involved from the outset. Prescribed fire is the primary tool used to restore upland savanna and was chosen by The Nature Conservancy to manage the lowland savanna. In open areas dominated by Reed canary grass (Phalaris arundinacea), fire was associated with reduced cover of this highly invasive species and an increase in native species richness. However, other results suggested that management options beyond the use of fire are needed to restore this lowland savanna. In retrospect, an approach that integrated the skills of researchers and managers at the outset of the study would have altered many of the restoration goals and processes. Pretreatment data, greater replication, and systematically varying treatments could have provided a more robust assessment of treatment effects. We recognize, however, that impediments in staffing, funding, and time were barriers to following this course of action.     

Parental genome composition and genetic classifications of derivatives from intergeneric crosses of Festuca mairei and Lolium perenne

Intergeneric hybridization between Festuca and Lolium has been a long-term goal of forage and turfgrass breeders to generate improved cultivars by combining stress tolerance of Festuca and rapid establishment of Lolium. However, wide-distance hybridizations usually result in the wild genome being eliminated from the hybrid due to incomplete chromosome pairing and crossovers. In this study, random amplified polymorphic DNA (RAPD) and simple sequence repeat (SSR) markers were used to detect the parental genome composition of F₁ hybrids and backcross, generated from crosses between Festuca mairei St. Yves (Fm) and Lolium perenne L. (Lp). Each of the hybrids exhibited integration of Fm and Lp genomes with varying levels of Fm/Lp genome ratios. However, cluster and principle component analyses of the progeny consistently revealed four groups depending on the amount of genome introgression from both parents. The parental genome composition and classifications of intergeneric progeny would be useful for breeding material selection. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

高羊茅MAPK基因的克隆与表达分析

丝裂原活化蛋白激酶(M APK)是生物体内信号转导的重要组分,与生长、发育和逆境胁迫反应密切相关.为了研究草坪草对非生物逆境胁迫反应的分子机理,利用同源基因克隆法从4℃低温诱导的草坪草高羊茅(F estu-ca arund inacea Schreb.)幼苗cDNA文库中分离得到一个M APK的cDNA即F aMAPK 1,F aMAPK 1编码369个氨基酸残基的蛋白激酶,该蛋白激酶具有TEY的磷酸化基序.据推测的氨基酸序列的BLA ST同源性分析表明,F aM APK 1蛋白与水稻O sM APK 4蛋白的一致性为91.1%.N orthern杂交检测F aMAPK 1基因对逆境胁迫反应的结果表明冷(4℃)处理对根中F aMAPK 1基因的表达没有明显影响,但诱导叶中F aMAPK 1上调表达.而且低温(4℃)、高盐(250 mm o l/L N aC l)、干旱和100μm o l/L ABA都诱导叶中F aMAPK 1上调表达,表明F aM APK 1蛋白可能在高羊茅对非生物逆境胁迫的反应中起重要作用.     

On the after‐use and restoration of abandoned extracted peatlands in the Baltic countries

In the Baltic countries (Estonia, Latvia, and Lithuania), mires directly affected by peat extraction cover almost 90,000 ha. Of these, over 26,200 ha have already been extracted and are abandoned. The main aim of this article is to give an overview of the extent of extracted peatlands in the Baltics, the legislative background around the land‐use options, and the directions of after‐use of peatlands since the middle of the 20th century. We also critically review results from restoration of abandoned extracted peatlands and assess whether they are on a trajectory toward reinitiation of paludification and functioning mire ecosystems. Almost all currently existing abandoned extracted peatlands in the Baltics were abandoned during and shortly after the Soviet period (1940–1991) without any restoration measures. The rest of the extracted areas were mostly afforested, converted into agricultural lands, berry plantations, or water bodies. The after‐use was mostly experimental, lacking systematic, proper assessment of outcome, cost and benefits, and side effects. The data are scarce but it could be estimated that only <10% (Estonia and Lithuania) and <20% (Latvia) of the total area of abandoned extracted peatlands were used for some purposes after peat extraction. Recently, several trials aimed at restoring the mire vegetation and ecosystem functions have been started in abandoned extracted peatlands in all three countries. In the coming years, the restoration of extracted peatlands in the Baltics will start on much bigger areas within different projects and initiatives cofinanced by the European Union.     

Infection with the fungal endophyte Epichloë festucae may alter the allelopathic potential of red fescue

Red fescue (Festuca rubra) is a perennial grass used as both forage and turfgrass. Asymptomatic plants of this species are systemically infected by the fungal endophyte Epichloë festucae, which has a beneficial effect on the infected plants. The aim of this study was to determine the effect of the endophyte Epichloë festucae on the allelopathic potential of F. rubra against four associated pasture species that are also considered as weeds in lawns, Trifolium pratense, Trifolium repens, Lotus corniculatus and Plantago lanceolata. Two experiments were designed to evaluate the allelopathic effect of extracts from the roots and leaves of endophyte‐infected (E+) and non‐infected (E?) plants on the germination and seedling growth of the four target species. Regardless of the endophyte status of the host plant, leaf extracts elicited a stronger reduction in germination and seedling growth than root extracts. Extracts from E+ plants reduced the speed of germination index of Trifolium spp. to a greater extent than those from E? plants. Radicle length of the target species was the parameter most affected by the presence of the endophyte in F. rubra. Root extracts from E+ plants had a greater inhibitory effect on the radicle growth of the target species than did root extracts from E? plants. A greater concentration in total phenolic compounds was found in the roots of E+ plants than of E?; however, this difference was not observed in the leaves. Thus, the allelopathic potential of F. rubra is altered in infected plants.     

Small-scale shifting mosaics of two dominant grassland species: the possible role of soil-borne pathogens

We analyzed the dynamics of dominant plant species in a grazed grassland over 17 years, and investigated whether local shifts in these dominant species, leading to vegetation mosaics, could be attributed to interactions between plants and soil-borne pathogens. We found that Festuca rubra and Carex arenaria locally alternated in abundance, with different sites close together behaving out of phase, resulting in a shifting mosaic. The net effect of killing all soil biota on the growth of these two species was investigated in a greenhouse experiment using gamma radiation, controlling for possible effects of sterilization on soil chemistry. Both plant species showed a strong net positive response to soil sterilization, indicating that pathogens (e.g., nematodes, pathogenic fungi) outweighed the effect of mutualists (e.g., mycorrhizae). This positive growth response towards soil sterilization appeared not be due to effects of sterilization on soil chemistry. Growth of Carex was strongly reduced by soil-borne pathogens (86% reduction relative to its growth on sterilized soil) on soil from a site where this species decreased during the last decade (and Festuca increased), while it was reduced much less (50%) on soil from a nearby site where it increased in abundance during the last decade. Similarly, Festuca was reduced more (67%) on soil from the site where it decreased (and Carex increased) than on soil from the site where it increased (55%, the site where Carex decreased). Plant-feeding nematodes showed high small-scale variation in densities, and we related this variation to the observed growth reductions in both plant species. Carex growth on unsterilized soil was significantly more reduced at higher densities of plant-feeding nematodes, while the growth reduction in Festuca was independent of plant-feeding nematode densities. At high plant-feeding nematode densities, growth of Carex was reduced more than Festuca, while at low nematode densities the opposite was found. Each plant species thus seems to be affected by different (groups of) soil-borne pathogens. The resulting interaction web of plants and soil-borne pathogens is discussed. We hypothesize that soil disturbances by digging ants and rabbits may explain the small-scale variation in nematode densities, by locally providing “fresh” sand. We conclude that soil-borne pathogens may contribute to plant diversity and spatial mosaics of plants in grasslands. Received: 19 January 2000 / Accepted: 11 April 2000