Nutrient status of vegetation grown in alkaline bauxite processing residue amended with gypsum and thermally dried sewage sludge - A two year field study

Although the treatments for overcoming the high pH and exchangeable sodium percentage (ESP) of bauxite residue are well known, there is little information on long-term nutrient management of vegetation after rehabilitation. The present study examined the chemical and physical amendment of fine fraction residue (red mud) at the Aughinish Alumina Ltd. Bayer Plant, Ireland followed by a two-year field investigation. Gypsum and sewage sludge were incorporated into the residue and amended mud sown with Lolium perenne and Holcus lanatus. Aerial portions were harvested and nutrient composition determined annually for the first two years growth. Amended substrate was low in manganese and magnesium. After year one herbage contained adequate calcium levels, but there were deficiencies for nitrogen, manganese, potassium and magnesium. Sodium levels were not considered excessive and levels declined further in year two. Levels for nitrogen, calcium, manganese, magnesium, phosphorous and potassium were also reduced in the second year. As levels were already deficient in year one the further decreases suggest severe nutrient shortage in the residue substrate. For long-term success of revegetation of bauxite residue, even after gypsum and organic amendment, the deficiencies of nutrients in the substrate must be overcome.     

Population dynamics of wireworms (Coleoptera,Elateridae) in arable land after abandonment

The community of elaterid larvae of three sites (field and two fallows), representing different stages of secondary succession, were studied using soil sampling from 1986 to 1993. All three sites were abandoned arable land: a field cultivated until 1991, a fallow I abandoned in 1986, and a fallow II abandoned about 1976. The fallow II was used as a meadow after abandonment and was regularly mown until 1985, when cultivation stopped. Six species of Elateridae larvae were found at all three study sites. In the field, Agriotes obscurus, Athous niger, Athous subsuscus, Dalopius marginatus and Athous vittatus were found, A. niger and A. obscurus being the most abundant species. During cultivation, larval densities were very low, however, larval abundance increased up to 8.8 ± 8.3 ind. m^-2 when cultivation stopped. Only small A. obscurus larvae were found during cultivation, whereas larval size increased after abandonment. In fallow I A. obscurus, A. niger, A. subsuscus, D. marginatus, and Agrypnus murinus were found and the average annual abundance fluctuated between 0.8 ± 1.4 to 40.8 ± 10.9 ind. m^-2 with A. obscurus being the most abundant species. Fallow II supported the highest densities of wireworms from all plots studied (71.2±35.2 to 280.0±24.8 ind. m^-2). A. obscurus, A. niger, A. subsuscus and D. marginatus were found in fallow II. The abundance of all larval Elateridae as well as the dominant species A. obscurus decreased during the study period, while simultaneously the occurrence of small sized A. obscurus larvae decreased. The frequency of cultivation and time elapsed since last cultivation appeared to be the most important factors affecting elaterid occurrence in the field and fallow I. In fallow II, the decrease in abundance correlates with the accumulation of a dense litter layer, which may correspond with soil surface structure, plant community changes or predator pressure.     

Biomass responses to elevated CO<Subscript>2</Subscript>, soil heterogeneity and diversity: an experimental assessment with grassland assemblages

While it is well-established that the spatial distribution of soil nutrients (soil heterogeneity) influences the competitive ability and survival of individual plants, as well as the productivity of plant communities, there is a paucity of data on how soil heterogeneity and global change drivers interact to affect plant performance and ecosystem functioning. To evaluate the effects of elevated CO₂, soil heterogeneity and diversity (species richness and composition) on productivity, patterns of biomass allocation and root foraging precision, we conducted an experiment with grassland assemblages formed by monocultures, two- and three-species mixtures of Lolium perenne, Plantago lanceolata and Holcus lanatus. The experiment lasted for 90 days, and was conducted on microcosms built out of PVC pipe (length 38 cm, internal diameter 10 cm). When nutrients were heterogeneously supplied (in discrete patches), assemblages exhibited precise root foraging patterns, and had higher total, above- and belowground biomass. Greater aboveground biomass was observed under elevated CO₂. Species composition affected the below:aboveground biomass ratio and interacted with nutrient heterogeneity to determine belowground and total biomass. Species richness had no significant effects, and did not interact with either CO₂ or nutrient heterogeneity. Under elevated CO₂ conditions, the two- and three-species mixtures showed a clear trend towards underyielding. Our results show that differences among composition levels were dependent on soil heterogeneity, highlighting its potential role in modulating diversity–productivity relationships. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible to authorized users.     

Phylogeny of tall fescue and related species using RFLPs

The wild species of tall fescue (Festuca arundinacea var.genuina Schreb.) represent a wide range of genetic variation and constitute potential germplasm for tall fescue improvement. Our objective was to evaluate genome specificity of the previously-identified DNA probes and to examine the phylogenetic relationship of tall fescue with six related species by using RFLP data. A total of 29 DNA probes from aPstI-genomic library of tall fescue were hybridized toEcoRI-orHindIII-digested DNA of 32 plants from sixFestuca species and fromLolium perenne L. Fifteen probes hybridized to all seven species. The remaining 14 probes showed differential hybridization patterns (i.e., ±), especially at the diploid and tetraploid levels. This hybridization pattern reflected genome divergence in these species. The DNA probes will be useful markers in breeding programs involving interspecific and intergeneric hybridization. Cluster analyses were performed using the average genetic distances calculated with the RFLP data from 53 probe-enzyme combinations. Generally, genotypes from the same species were grouped in the same cluster. These data indicated that tall fescue has a close relationship withF. pratensis Huds. (diploid),F. arundinacea var.glaucescens Boiss. (tetraploid), andL. perenne L. (diploid) and thatFestuca pratensis andL. perenne had the closest degree of relationship.This paper is a contribution of the Missouri Agricultural Experimental Station, Journal Series no. 11,798     

Temporal and spatial patterns of soil water following wildfire-induced changes in plant communities in the Great Basin in Nevada,USA

Infection of tall fescue (Festuca arundinacea Schreb.) with its endemicNeotyphodium coenophialum-endophyte (Morgan-Jones and Gams) Glenn, Bacon and Hanlin appears to reduce copper (Cu) concentrations in forage and serum of grazing animals, contributing to a range of immune-related disorders. A greenhouse experiment was conducted to identify effects of novel endophyte strains on Cu acquisition by tall fescue (Festuca arundinacea Schreb.) varieties Grasslands Flecha and Jesup infected with a novel, non ergot producing endophyte strain AR542, and two perennial ryegrass (Lolium perenne L.) varieties Aries and Quartet infected with a novel, non lolitrem B producing strain AR1, and their noninfected (E−) forms. Individual endophyte/grass associations were cultivated in nutrient solutions at 1.0 (P+) and 0.0 mM (P−) phosphorus concentrations. The Cu²⁺-binding activity of extracellular root exudates, and concentrations of Cu and other heavy metals in roots and shoots were measured. Extracellular root exudates of AR542-infected vs. E− tall fescue had higher Cu²⁺-binding activity only in P− nutrient solution as shown by lower concentration of free Cu²⁺ (0.096 vs. 0.188 mmol Cu²⁺ g⁻¹ root DM, respectively). The Cu²⁺-binding activity by root exudates of perennial ryegrass was not affected by endophyte infection, but was higher (i.e., lower concentration of free Cu²⁺) in P− vs. P+ nutrient solution (0.068 vs. 0.114 mmol Cu²⁺ g⁻¹ root DM). In this hydroponic experiment, Cu concentrations in shoots of both grasses were not a function of Cu²⁺-binding activity and endophyte effects on heavy metal concentrations in shoots and roots were specific for each variety. The Cu²⁺-binding activity of extracellular root exudates may affect Cu accumulation by field-grown, endophyte-infected tall fescue under P-limiting growth conditions and warrants verification by more specific methods.     

Transgenic ryegrasses (Lolium spp.) with down-regulation of main pollen allergens

Ryegrass pollen (Lolium species) is a widespread source of air-borne allergens and is a major cause of hayfever and seasonal allergic asthma, which affect approximately 25% of the population in cool temperate climates. The main allergens of ryegrass pollen are the proteins Lol p 1 and Lol p 2. These proteins belong to two major classes of grass pollen allergens to which over 90% of pollen-allergic patients are sensitive. The functional role in planta of these pollen allergen proteins remains largely unknown. Here we describe the generation and analysis of transgenic plants with reduced levels of the main ryegrass pollen allergens, Lol p 1 and Lol p 2 in the most important worldwide cultivated ryegrass species, L. perenne and L. multiflorum. These transgenic plants will allow the study of the functional role in planta of these pollen proteins and the determination of potential for development of hypo-allergenic ryegrass cultivars.     

Size and morphology of root systems of perennial grasses from contrasting habitats as affected by nitrogen supply

This paper discusses interspecific differences and phenotypic responses to nitrogen supply in various root parameters of five perennial grasses from contrasting habitats. The following root parameters were studied: root:shoot ratio, specific root length, specific root area, mean root diameter, frequency of fine roots, and the length and density of root hairs. Significant between-species variation was found in all of these features. Species from fertile sites had higher root:shoot ratios at high nitrogen supply than species from infertile habitats. All species growing at low nitrogen supply showed a significant increase in root:shoot ratio. Specific root length, specific root area, mean root diameter and frequency of fine roots were not affected significantly by nitrogen supply. Species from infertile sites responded to low nitrogen supply by a significant increase in root hair length and root hair density.     

不同种植方式下两种草本营养元素对土壤厚度和水分减少的响应

为了探究不同种植方式下草本植物对喀斯特"土层浅薄"和"岩溶干旱"生境的养分调节响应,选择苇状羊茅(Festuca arundinacea)和黑麦草(Lolium perenne)为研究材料,在盆栽水分控制条件下设置了2种土壤厚度[对照土壤厚度(T_(CK))和浅土(T_S)]、2种水分处理[对照水分(W_(CK))和干旱(W_D)]和2种种植方式(单种和混种),研究土壤厚度和水分减少对混种下两种草本植物元素含量、积累和分配的影响。结果表明:(1)与对照组(CK:T_(CK)W_(CK))相比,在浅土组(S:T_SW_(CK))、干旱组(D:T_(CK)W_D)和浅土+干旱组(SD:T_SW_D),苇状羊茅和黑麦草的地上和根系C和N含量在单种和混种下(浅土除外)显著增加,P含量和各部分元素积累量显著降低;而苇状羊茅的根系各元素分配比在3种低资源水平下(S、D、SD)由单种时增加转为混种时降低,而黑麦草的根系营养元素分配比在浅土中增加,但在干旱处理下减少。(2)在对照资源水平下(CK),混种后苇状羊茅的地上部分C含量、根系P含量、地上、地下和总的元素积累量和根系元素分配比显著高于单种,而在3种低资源水平下达到各参数在单种和混种下无显著差异。(3)在各资源水平下,混种后黑麦草各部分C、N、P的含量、积累量和根系元素分配比大体上与单种无显著差异。结果表明,在低资源水平下,苇状羊茅和黑麦草通过增加C和N元素含量表现出较强的资源获取和防御能力。在混种条件下,苇状羊茅能够通过调节自身元素的积累和分配来提高竞争力,而黑麦草保持相对恒定的策略来响应竞争。     

Loss of exudates from the roots of perennial ryegrass inoculated with a range of micro-organisms

To determine the effect of microbial metabolites on the release of root exudates from perennial ryegrass, seedlings were pulse labelled with [¹⁴C]-CO₂ in the presence of a range of soil micro-organisms. Microbial inoculants were spatially separated from roots by Millipore membranes so that root infection did not occur. Using this technique, only microbial metabolites affected root exudation. The effect of microbial metabolites on carbon assimilation and distribution and root exudation was determined for 15 microbial species. Assimilation of a pulse label varied by over 3.5 fold, dependent on inoculant. Distribution of the label between roots and shoots also varied with inoculant, but the carbon pool that was most sensitive to inoculation was root exudation. In the absence of a microbial inoculant only 1% of assimilated label was exuded. Inoculation of the microcosms always caused an increase in exudation but the percentage exuded varied greatly, within the range of 3–34%.     

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.     

Fatality of house crickets on perennial ryegrasses infected with a fungal endophyte

Plants of perennial ryegrass, Lolium perenne L., infected with an endophytic fungus, Acremonium loliae Latch et al. were toxic to house crickets, Acheta domesticus L. Death followed progressive inactivity, culminating in 100% cricket mortality by 84 h. The epithelial lining of the crop and proventriculus of affected crickets was progressively loosened and detached, resulting in complete failure of the alimentary process.Besides the house cricket which is an acridid, antibiosis of a number of coleopterous and lepidopterous pests on endophyte-infected ryegrasses has been previously reported. Thus, the endophyte is an important source of insect resistance which plant breeders can incorporate into new crop varieties.

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Résumé Des expériences ont été faits sur des grillons, Acheta domesticus L., avec des plantes de raygrass vivaces, Lolium perenne L., qui étaient, ou non-infectées par un champignon endophyte, Acremonium loliae Latch, Christensen et Samuels. Les grillons se nourrisant de raygrass infectés ont montré un degré de mortalité beaucoup plus elevé, en 48 heures, que les grillons se nourrissant de raygrass non-infectés. En l'espace de 84 heures, les grillons se nourrissant des trois sortes de raygrass infectés ont montré un pourcentage de mortalité de 100%. La mort a suivi l'inactivité progressive qui est symptomatique des inhibiteurs métaboliques.Les dissections de grillons paralysés ont révélé l'existence d'un estomac antérieur distendu et plus transparent. Le proventricule aussi était transparent, mais moins que l'estomac antérieur. La transparence de l'estomac antérieur, spécialement le jabot, a résulté d'une extension progressive et du ramollissement de l'épithélium intestinal et des groupes de muscles longitudinaux insérés dedans, et éventuellement ces cellules sont éliminées. Ces profonds changements histopathologiques inhibent apparemment le fonctionnement de l'estomac antérieur du grillon avec comme résultat l'inhibition de tout le processus alimentaire.En plus, des excroissances ressemblant à des tumeurs ont été observées dans les jabot des grillons, qui avaient été nourris d'un des trois raygrass infectés par le champignon endophyte. Apparemment, ces excroissances anormales ont été les résultats de l'activation prématurée des groupes de nidi. Quand elles étaient pleinement formées, ces masses se sont séparées de l'épithélium du jabot et ont obstrué la lumière. L'étude de l'étologie et de la pathologie de ces excroissances anormales requiert un travail supplémentaire.Les raygrass infectés par un champignon endophyte sont toxiques pour un certain nombre d'éspèces différentes d'insectes, tels que le Argentine stem weevil Listronotus bonariensis (Kuschel), le bluegrass billbug Sphenophorus parvulus (Gyllenhal) et les larves de sod webworm lépidoptères (plusieurs orthographes). Ainsi, l'endophyte est une source importante de résistance des insectes que les éleveurs de plantes peuvent incorporer donc les nouvelles variétés de cultures.

     

Decomposition of leaf and root tissue of three perennial grass species grown at two levels of atmospheric CO2 and N supply

Leaf and root tissue of Lolium perenne L., Agrostis capillaris L. and Festuca ovina L. grown under ambient (350 μl l^-1 CO₂) and elevated (700 μl l^-1) CO₂ in a continuously ¹⁴C-labelled atmosphere and at two soil N levels, were incubated at 14°C for 222 days. Decomposition of leaf and root tissue grown in the low N treatment was not affected by elevated [CO₂], whereas decomposition in the high N treatment was significantly reduced by 7% after 222 days. Despite the increased C/N ratio (g g^-1) of tissue cultivated at elevated [CO₂] when compared with the corresponding ambient tissue, there was no significant correlation between initial C/N ratio and ¹⁴C respired. This finding suggests that the CO₂-induced changes in decomposition rates do not occur via CO₂-induced changes in C/N ratios of plant materials. We combined the decomposition data with data on ¹⁴C uptake and allocation for the same plants, and give evidence that elevated [CO₂] has the potential to increase soil C stores in grassland via increasing C uptake and shifting C allocation towards the roots, with an inherent slower decomposition rate than the leaves. An overall increase of 15% in ¹⁴C remaining after 222 days was estimated for the combined tissues, i.e., the whole plants; the leaves made a much smaller contribution to the C remaining (+6%) than the roots (+26%). This shows the importance of clarifying the contribution of roots and leaves with respect to the question whether grassland soils act as a sink or source for atmospheric CO₂. This revised version was published online in June 2006 with corrections to the Cover Date.     

Transformation of recalcitrant turfgrass cultivars through improvement of tissue culture and selection regime

Tissue culture techniques, medium composition, pH value and targeted tissues, agroinfection and co-culture conditions, selection process were optimized for efficient turfgrass transformation. A highly regenerable callus lines were produced in callus induction medium modified from N6 basal medium. Six-week-old calluses were cultured on Pre-regeneration medium I for 4 days and then subjected to Agrobacterium tumefaciens. After co-cultivation at 20±1 °C in a 16 h light/8 h darkness for 3 days, the calluses were cultured on non-selective Pre-regeneration medium II supplemented with 400 mg l⁻¹ l-cysteine for 7 days. Plantlets were regenerated on the Regeneration medium without selection pressure. A selection pressure was given to the regenerated plantlets when they were rooted on the Plantlet rooting medium. Roots appeared within 8–12 days in putative transformed plantlets. Resistant plants obtained were phenotypically normal and fully fertile. Chemical and molecular analyses confirmed that foreign genes were successfully introduced into the genome of perennial ryegrass or tall fescue. The transformation efficiency can attain 23.3% in perennial ryegrass.     

15N estimates of nitrogen fixation by white clover (Trifolium repens L.) growing in a mixture with ryegrass (Lolium perenne L.)

The ¹⁵N isotope dilution technique and the N difference method were used to estimate N₂ fixation by clover growing in a mixture with ryegrass, in a field experiment and a controlled environment experiment. Values obtained using N difference were approximately 25% lower than those estimated using ¹⁵N isotope dilution. In the field experiment there was a measured N benefit to grass growing with clover, equivalent to 42.7 kgN ha^-1. The grass in the mixture had a lower atom %¹⁵N content and a higher N content than grass in a monoculture; therefore values for N₂ fixation were different depending on choice of control plant i.e. monoculture or mixture grass. In the controlled environment experiment there were no significant differences between either the atom %¹⁵N contents or the N contents of monoculture grass and grass growing in a mixture with clover. It is concluded that there is a long term indirect transfer of N from clover to associated grass which can lead to errors in estimates of N₂ fixation.     

Food preference of the trichopteran larva Anabolia nervosa from two streams with different food availability

The food preference of the trichopteran shredder Anabolia nervosa from two streams with different food availability was studied in laboratory preference experiments. One stream was unshaded and had abundant growth of the submerged macrophyte Potamogeton perfoliatus. The other was shaded by trees (Alnus glutinosa) and had very sparse growth of submerged macrophytes. To test the food preference of Anabolia nervosa for terrestrial leaf litter and submerged plants we offered leaves of: conditioned Alnus glutinosa, fresh green Alnus, conditioned Fagus sylvatica, fresh green Fagus, and fresh submerged Potamogeton perfoliatus. For both larval populations conditioned Alnus was the most consumed food item, followed by Potamogeton. Larvae from the Alnus-shaded stream preferred conditioned Alnus over all other food items, while larvae from the macrophyte stream did not clearly discriminate between conditioned Alnus and Potamogeton. The three remaining food items were largely rejected. Food items were analyzed for dry matter, organic matter, fibre, nitrogen, phosphorus and toughness. Preference was not correlated to any of these food characteristics, but we suggest that they may still be important and influence food choice in a complex manner. The study indicates that the preference pattern of Anabolia nervosa is not clearly related to previous feeding habituation. The ability to feed on fresh Potamogeton is, therefore, not acquired by certain populations of larvae through long exposure to this resource in the field. The high preference for fresh Potamogeton suggests that Anabolia nervosa may actively select Potamogeton as food even when alternative food sources such as terrestrial leaf litter are abundant in the field.     

Frankia in the rhizosphere of nonhost plants: A comparison with root-associated N2-fixing Enterobacter,Klebsiella and Pseudomonas

Bacterial growth in the rhizosphere and resulting changes in plant growth parameters were studied in small aseptic seedlings of birch (Betula pendula and B. pubescens) and grasses (Poa pratensis and Festuca rubra). The seedlings were inoculated with three Frankia strains (Ai1a and Ag5b isolated from native Alnus root nodules and Ai17 from a root nodule induced by soil originating from a Betula pendula stand), and three associative N₂-fixing bacteria (Enterobacter agglomerans, Klebsiella pneumoniae and Pseudomonas sp., isolated from grass roots). Microscopic observations showed that all the Frankia strains were able to colonize and grow on the root surface of the plants tested without addition of an exogenous carbon source. No net growth of the associative N₂-fixers was observed in the rhizosphere, although inoculum viable counts were maintained over the experimental period. Changes in both the biomass and morphology of plant seedlings in response to bacterial inoculation were recorded, which were more dependent on the plant species than on the bacterial strain.