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Most studies on plant‐soil feedback (PSF) and plant competition measure the feedback response at one moment only. However, PSFs and competition may both change over time, and how PSF and competition interact over time is unclear.We tested the temporal dynamics of PSF and interspecific competition for the forb Jacobaea vulgaris and the grass Holcus lanatus. We grew both species individually and in interspecific competition in soil that was first conditioned in the greenhouse by J. vulgaris, by H. lanatus or without plant growth. For a period of 11 weeks, we harvested plants twice a week and analysed the fungal and chemical composition of the different soils at the end of the first and second growth phase.During the second growth phase, when grown in isolation, both species produced more biomass in heterospecific conditioned soil than in conspecific conditioned soil. Young J. vulgaris exhibited a strong negative conspecific feedback, but this effect diminished over time and became neutral in older plants. In contrast, when grown in competition, the negative conspecific feedback of J. vulgaris exacerbated over time. Older H. lanatus plants benefited more from heterospecific conditioning when competing with J. vulgaris, then when grown isolated.Fungal community composition and soil chemistry differed significantly between soils but this was mainly driven by differences between plant‐conditioned and unconditioned soils. Remarkably, at the end of the second growth phase, fungal community composition was not explained by the legacy of the species that had been grown in the soil most recently, but still reflected the legacy of the first growth phase. We reexamined plant growth during a third growth phase. Biomass of J. vulgaris was still influenced by the treatments imposed during the first phase, while H. lanatus responded only to the plant growth treatments imposed during the second phase.Synthesis. Our study shows that the direction and magnitude of PSF depends on plant age and competition, and also on soil legacy effects of earlier plant growth. These results highlight the need to incorporate dynamic PSFs in research on plant populations and communities. This study shows that the direction and magnitude of plant‐soil feedback (PSF) varies greatly and depends on plant age and on whether the plant competes or not. However, PSF also depends on soil legacy effects of plant growth two generations earlier. These results highlight the need to incorporate dynamic PSFs in research on plant populations and communities. [ABSTRACT FROM AUTHOR]

A significant proportion of arsenic (As)-contaminated sites are temporarily or permanently under reducing condition, which may affect phytoextraction efficiency using the As-hyperaccumulator Pteris vittata L. In this work, a pot experiment was conducted to investigate the solubility and redox species of As in soil. The uptake of As by two populations of P. vittata and As-tolerant grass Holcus lanatus under different water regimes was examined. Waterlogging decreased the redox potential from 350 to−50 mV, leading to an approximately 40% reduction of As(V) to As(III) and an increased dissolved As concentration by 150%–300%. The changes in the speciation and concentration of As influenced its uptake by plants. A population collected from a temporarily waterlogged riverside in Guangxi province (GX population) had ninefold higher shoot As concentration under the waterlogged condition than that under the non-waterlogged condition, indicating that it preferred taking up As in the form of As(III). By contrast, a population of P. vittata collected from a dry land in Yunnan province (YN population) and H. lanatus demonstrated a preference to As(V). The GX population was an appropriate species for the phytoextraction of waterlogged sites. These results implied the importance of habitat ecology on the extraction efficiency of hyperaccumulators. [ABSTRACT FROM AUTHOR]

Alternative stable states have long been thought to exist in natural communities, but direct evidence for their presence and for the environmental switches that cause them has been scarce. Using a combination of greenhouse and field experiments, we investigated the environmental drivers associated with two distinctive herbaceous communities in coastal ecosystems in New Zealand. In a mosaic unrelated to micro-topography, a community dominated largely by native turf species (notably Leptinella dioica, Samolus repens, and Selliera radicans) alternates with vegetation comprising exotic (i.e., nonnative) pasture species (notably Agrostis stolonifera, Holcus lanatus, Lolium perenne, and Trifolium repens). The species of these two communities differ in functional characters related to leaf longevity and growth rate, and occupy soils of differing nitrogen levels. Both spatial and environmental factors influenced the species composition locally. Reciprocal transplants of soil, with and without associated vegetation, showed that a native turf community developed when sward or soil from either community was bounded by turf, and a pasture community developed when sward or soil from either community was surrounded by pasture. In artificial mixed communities in the greenhouse, turf was able to invade the pasture community where the vegetation was clipped to simulate grazing, and also where Trifolium was removed and/or salt spray was applied. The pasture community invaded the turf where Trifolium was present or nitrogen was added. These results were supported by trends in experimentally manipulated field plots, where the amount of turf cover increased when nitrogen was kept low and when salt spray was applied, whereas pasture cover increased in the absence of salt spray. Thus, persistence of the native turf community is dependent on grazing, both directly and via its effect on keeping nitrogen levels low by excluding the exotic, nitrogen-fixing Trifolium, and by exposing the vegetation to salt spray. If any of these factors change, there could be a state change to pasture dominance that might be resistant to reversion to turf. Managing such coastal herbaceous communities therefore requires an understanding of the environmental and species characteristics that maintain alternative states. [ABSTRACT FROM AUTHOR]

The aim of this study was to characterize the transcriptome of a balanced polymorphism, under the regulation of a single gene, for phosphate fertilizer responsiveness/arsenate tolerance in wild grass Holcus lanatus genotypes screened from the same habitat., De novo transcriptome sequencing, RNAseq (RNA sequencing) and single nucleotide polymorphism ( SNP) calling were conducted on RNA extracted from H. lanatus. Roche 454 sequencing data were assembled into c. 22 000 isotigs, and paired-end Illumina reads for phosphorus-starved (P−) and phosphorus-treated ( P+) genovars of tolerant ( T) and nontolerant ( N) phenotypes were mapped to this reference transcriptome., Heatmaps of the gene expression data showed strong clustering of each P+/ P− treated genovar, as well as clustering by N/ T phenotype. Statistical analysis identified 87 isotigs to be significantly differentially expressed between N and T phenotypes and 258 between P+ and P− treated plants. SNPs and transcript expression that systematically differed between N and T phenotypes had regulatory function, namely proteases, kinases and ribonuclear RNA-binding protein and transposable elements., A single gene for arsenate tolerance led to distinct phenotype transcriptomes and SNP profiles, with large differences in upstream post-translational and post-transcriptional regulatory genes rather than in genes directly involved in P nutrition transport and metabolism per se. [ABSTRACT FROM AUTHOR]

Yorkshire fog ( Holcus lanatus), which belongs to the Poaceae family and is a close relative of the agronomic crop oat ( Avena sativa), is a widely adaptable grass species that is able to grow on highly acidic soils with high levels of Al, but the mechanism underlying the high Al tolerance is unknown. Here, we characterized two accessions of H. lanatus collected from an acid plot (soil pH 3.6, HL- A) and a neutral plot ( pH 7.1, HL- N) in terms of Al tolerance, organic acid anion secretion and related gene expression. In response to Al (pH 4.5), the HL- A roots secreted approximately twice as much malate as the HL- N roots, but there was no difference in citrate secretion. Cloning of the gene HlALMT1 responsible for malate secretion showed that the encoded amino acid sequence did not differ between two accessions, but the expression level in the outer cell layers of the HL- A roots was twice as high as in the HL- N roots. This difference was not due to the genomic copy number, but was due to the number of cis-acting elements for an Al-responsive transcription factor ( Hl ART1) in the promoter region of HlALMT1, as demonstrated by both a yeast one-hybrid assay and a transient assay in tobacco protoplasts. Furthermore, introduction of HlALMT1 driven by the HL-A promoter into rice resulted in significantly more Al-induced malate secretion than introduction of HlALMT1 driven by the HL-N promoter. These findings indicate that the adaptation of H. lanatus to acidic soils may be achieved by increasing number of cis-acting elements for ART1 in the promoter region of the HlALMT1 gene, enhancing the expression of HlALMT1 and the secretion of malate. [ABSTRACT FROM AUTHOR]

The greenbug, Schizaphis graminum (Rondani), is a major pest of cereals in some parts of the world and is of particular concern because it can be resistant to some insecticides and overcome the resistance of crops. In the UK, it has never been found on crops, but two rather little-known and closely-related species (Schizaphis holci and Schizaphis agrostis) are associated with the wild grasses, Holcus lanatus and Agrostis stolonifera. Since 1987, winged (alate) aphids morphologically resembling the greenbug have been found in increasing numbers in 12.2 m high suction-trap samples of the Rothamsted Insect Survey (RIS); hence, studies were undertaken to establish their identity. Clones (=asexual lineages) established from populations collected from H. lanatus in southern England showed strong preference for Holcus over Agrostis and Hordeum in laboratory tests and produced sexual morphs when transferred to short-day conditions, the males being apterous, as expected for S. holci. Multivariate morphometric comparisons of alatae caught in UK RIS suction traps in 2007 and 2011 with named specimens from museum collections, including S. graminum from many countries, indicated that the suction-trapped alatae were mostly S. agrostis and S. holci. Cytochrome c oxidase subunit I (COI) mtDNA obtained from 62 UK specimens from suction-traps had 95.4–100% sequence identity with US specimens of S. graminum. Two of the UK specimens had identical COI sequence to the US sorghum-adapted form of S. graminum, and these specimens also had 100% identity with a 640 bp fragment of nDNA CytC, indicating that this form of S. graminum may already be present in the UK. Present and future economic implications of these results are discussed. [ABSTRACT FROM AUTHOR]

Four kinds of soil material were used in a pot experiment with velvetgrass (Holcus lanatus). Two unpolluted soils: sand (S) and loam (L) were spiked with sodium arsenite (As III) and arsenate (As V), to obtain total arsenic (As) concentrations of 500 mg As kg−1. Two other soils (ZS I, ZS III), containing 3320 and 5350 mg As kg−1, were collected from Zloty Stok where gold and arsenic ores were mined and processed for several centuries. The effects of phosphate addition on plants growth and As uptake were investigated. Phosphate was applied to soils in the form of NH4H2PO4 at the rate 0.2 g P/kg. Average concentrations of arsenic in the shoots of velvetgrass grown in spiked soils S and L without P amendment were in the range 18–210 mg As kg−1 d.wt., whereas those in plants grown on ZS I and ZS II soils were considerably lower, and varied in the range 11–52 mg As kg−1 d.wt. The addition of phosphate caused a significant increase in plant biomass and therefore the total amounts of As taken up by plants, however, the differences in As concentrations in the shoots of velvetgrass amended and non-amended with phosphate were not statistically significant. [ABSTRACT FROM PUBLISHER]

Abstract: Arsenate and arsenite sensitivity and arsenate influx tests were conducted for two rice cultivars of different arsenic sensitivity, Azucena and Bala. These were to establish if the mechanism of reduced arsenic sensitivity is achieved through an altered phosphate uptake system, as shown for Holcus lanatus. High phosphate treatments (≥50μM) provided protection against both arsenate and arsenite. Unlike the H. lanatus tolerance mechanism, in the less sensitive cultivar Bala, arsenate influx did not decrease with phosphate treatment and phosphate transporters appeared to be constitutively upregulated; V max for arsenate influx remain similar when Bala was grown in the presence or absence of phosphate (V max – 0.90 and 0.63nmolg−1 f.wtmin−1 respectively). Although mean K m appear different, Bala did not show lower affinity to arsenate than Azucena in the absence of phosphate (K m – Azucena, 0.30mM and Bala, 0.18), while in phosphate treatment, Bala arsenate affinity was half that observed for Azucena (K m – Azucena, 0.14 and Bala, 0.36mM). These were low compared to a 4 and 6 fold decrease seen for similar studies on H. lanatus in the absence and presence of phosphate. Phosphate-induced arsenic protection was observed but the mechanism does not resemble that of H. lanatus. Alternative mechanisms were discussed. [Copyright &y& Elsevier]

* Premise of the study: Invasive plants represent a significant threat to ecosystem biodiversity. To decrease the impacts of invasive species, a major scientific undertaking of the last few decades has been aimed at understanding the mechanisms that drive invasive plant success. Most studies and theories have focused on a single mechanism for predicting the success of invasive plants and therefore cannot provide insight as to the relative importance of multiple interactions in predicting invasive species' success. * Methods : We examine four mechanisms that potentially contribute to the success of invasive velvetgrass Holcus lanatus : direct competition, indirect competition mediated by mammalian herbivores, interference competition via allelopathy, and indirect competition mediated by changes in the soil community. Using a combination of field and greenhouse approaches, we focus on the effects of H. lanatus on a common species in California coastal prairies, Erigeron glaucus, where the invasion is most intense. * Key results : We found that H. lanatus had the strongest effects on E. glaucus via direct competition, but it also influenced the soil community in ways that feed back to negatively influence E. glaucus and other native species after H. lanatus removal. * Conclusions : This approach provided evidence for multiple mechanisms contributing to negative effects of invasive species, and it identified when particular strategies were most likely to be important. These mechanisms can be applied to eradication of H. lanatus and conservation of California coastal prairie systems, and they illustrate the utility of an integrated set of experiments for determining the potential mechanisms of invasive species' success. [ABSTRACT FROM AUTHOR]

Velvet grass (Holcus lanatus L.) has a great potential use for winter pasture in subtropical regions due to its good establishment, persistence, high forage production, cold resistance, palatability and tillering ability. The objective of this work was to estimate genetic variability and heritability of agronomic traits and to identify superior progenies. Sixty half-sib progenies were assessed for natural height at the vegetative stage (NH), plant diameter (diameter), heading date (cycle), final height (after flowering) (FH), and tiller number (tillers). Difference among progenies was observed for all traits. Heritability estimates were 38%, 32%, 92%, 57% and 64% for NH, diameter, cycle, FH and tillers, respectively. The highest genetic gain estimate was 30.77 % for the tiller number. There is genetic variability for all the traits and gains after selection among halfsib progenies can be expected. [ABSTRACT FROM AUTHOR]

Plant species produce litter of varying quality and differ in the quality and quantity of compounds they release from live roots, which both can induce different decomposer growth in the soil. To test whether differences in decomposer growth can forecast the amount of N species acquire from plant litter, as suggested by theory, we grew individuals of three grassland plants— Holcus lanatus, Plantago lanceolata and Lotus corniculatus—in soils into which 15N-labelled litter of either Holcus, Plantago or Lotus was added. We measured the effects of live roots and litter of each species on soil microbes and their protozoan and nematode feeders, and to link decomposer growth and plant nutrient uptake, we measured the amount of N taken up by plants from the added litter. We hypothesised that those species that induce the highest growth of microbes, and especially that of microbial feeders, will also take up the highest amount of N from the litter. We found, however, that although numbers of bacterial-feeding Protozoa and nematodes were on average lower after addition of Holcus than Plantago or Lotus litter, N uptake was higher from Holcus litter. Further, although the effects on Protozoa and bacterial- and fungal-feeding nematodes did not differ between the live plants, litter-N uptake differed, with Holcus being the most efficient compared to Plantago and Lotus. Hence, although microbes and their feeders unquestionably control N mineralization in the soil, and their growth differs among plant species, these differences cannot predict differences in litter-N uptake among plant species. A likely reason is that for nutrient uptake, other species-specific plant traits, such as litter chemistry, root proliferation ability and competitiveness for soil N, override in significance the species-specific ability of plants to induce decomposer growth. [ABSTRACT FROM AUTHOR]

Belowground mechanisms involved in plant competition are still poorly understood. Since plant species are differently affected by soil organisms, changes in soil community composition might affect interspecific competition with consequences for plant community structure. We studied whether soil community composition affects competition between the grass Holcus lanatus L. and the legume Lotus corniculatus L. We established three different soil communities by adding no soil organisms (control), microorganisms <30 μm, and a soil suspension including microorganisms >30 μm, AMF and nematodes to gamma-sterilized soil. Nodulation and aboveground biomass of Lotus was decreased in the sterilized control soil and in the presence of Holcus. Contrastingly, the grass grew better in the presence of the legume than in monoculture and was not affected by soil community composition. Legume monocultures tended to produce the greatest aboveground biomass of the plant combinations when soil microorganisms were present, while the root biomass in legume monocultures was the lowest. Then, in a second experiment, we used natural (not sterilized) soil and added activated carbon to test whether the reduced nodulation of Lotus in interspecific competition is caused by allelopathic compounds of Holcus. In the natural soil, nodulation and flowering of Lotus was reduced, but the aboveground biomass was not affected by the competition with Holcus. Contrary to our expectations, activated carbon had a strong negative effect on the nodulation, growth and flowering of Lotus and shifted the interspecific competition in favour of Holcus. Probably, activated carbon impeded the nodulation by disrupting the communication between the legume and N2-fixing bacteria. We suggest that interruption of plant-microbe communications by activated carbon might be widespread and will confound interpretations on the role of allelopathy. Generally, we observed that the symbiosis of the legume with N2-fixing bacteria plays a crucial role in the grass-legume competition. When the symbiosis was deterred, the legume was outcompeted by the grass. [ABSTRACT FROM AUTHOR]

An outdoor experiment was conducted to increase understanding of apical leaf necrosis in the presence of pathogen infection. Holcus lanatus seeds and Puccinia coronata spores were collected from two adjacent and otherwise similar habitats with differing long-term N fertilization levels. After inoculation, disease and necrosis dynamics were observed during the plant growing seasons of 2003 and 2006. In both years high nutrient availability resulted in earlier disease onset, a higher pathogen population growth rate, earlier physiological apical leaf necrosis onset and a reduced time between disease onset and apical leaf necrosis onset. Necrosis rate was shown to be independent of nutrient availability. The results showed that in these nutrient-rich habitats H. lanatus plants adopted necrosis mechanisms which wasted more nutrients. There was some indication that these necrosis mechanisms were subject to local selection pressures, but these results were not conclusive. The findings of this study are consistent with apical leaf necrosis being an evolved defence mechanism. [ABSTRACT FROM AUTHOR]

The article is an overview of a study conducted by L. Crémieux and colleagues, which examined the adaptability of locally dislocated plants to genetically different types of antagonists. Holcus lanatus, a grass species, adapted to foreign insects but maladapted to new fungal pathogens. These divergent outcomes could be explained in terms of the varying ability of the two types of foreign antagonists to adapt to their new host, said the researchers. It is assumed that pathogens have evolutionary advantage over hosts because of their shorter generation time.

The effect of ozone on leaf gas diffusion was investigated by analyzing the stable oxygen isotopic signatures (δ18O) in leaves of Holcus lanatus L., Plantago lanceolata L., Ranunculus friesianus (Jord.), and Trifolium pratense L. grown in temperate, semi-natural grassland. Dried material from plants exposed to ambient or elevated ozone levels in a long-term free-air experiment was sampled in 2002 and 2003. A general increase in δ18O in elevated ozone indicated increased limitation to gas diffusion, which was strongest during the driest and warmest period in 2003. In three out of four species, the increase in δ18O paralleled an increase in δ13C measured earlier in the same samples, meaning that the dominant effect of ozone was on gas diffusion and not on CO2 fixation. Only in R. friesianus, ozone affected both processes simultaneously. It is concluded that elevated ozone not only affects productivity, but also the water status of important component species of grassland communities. [Copyright &y& Elsevier]

A new species of Holcus L. (Poaceae), endemic to the Azores archipelago (Portugal), is described. The vegetative and reproductive structures were studied. The diagnostic characters were compared with those of closely related species. New chromosome counts in Holcus azoricus M. Seq. & Castrov. (2 n = 35) and H. rigidus Hochst. (2 n = 28) are included. A possible hybrid origin is hypothesized; the potential parents are H. lanatus L. and H. rigidus. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 154, 259–267. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Patterns of resource availability and heterogeneity shape the composition, productivity, and dynamics of plant assemblages in a wide variety of terrestrial ecosystems. Despite this, the responses of plant assemblages to simultaneous changes in the availability and heterogeneity of more than a single resource are virtually unknown. To fill this gap, microcosms consisting of assemblages formed by Lolium perenne, Plantago lanceolata, Anthoxantum odoratum, Holcus lanatus, and Trifolium repens were grown in a factorial experiment with the following treatments: nutrient availability (NA), water availability (WA), spatial nutrient heterogeneity (NH), and temporal water heterogeneity (WH). Assemblages exhibited precise root foraging patterns in response to nutrient heterogeneity, which were modified by NA and WA. A series of two- and three-way interactions involving the four factors evaluated determined biomass production, the belowground : aboveground biomass ratio, the patterns of root biomass allocation with depth, and the relative contribution to aboveground biomass of Lolium and Anthoxanthum. In all cases, these interactions explained significant amounts of the variation found in the data. Our study demonstrates that considering the interactions between resource availability and heterogeneity allows for a refinement of predictions that can detectably reduce the error associated with extrapolating from single factor analyses. [ABSTRACT FROM AUTHOR]

Changes in the atmospheric concentration of carbon dioxide ([CO2]), nutrient availability and biotic diversity are three major drivers of the ongoing global change impacting terrestrial ecosystems worldwide. While it is well established that soil nutrient heterogeneity exerts a strong influence on the development of plant individuals and communities, it is virtually unknown how nutrient heterogeneity and global change drivers interact to affect plant performance and ecosystem functioning. We conducted a microcosm experiment to evaluate the effect of simultaneous changes in [CO2], nutrient heterogeneity (NH), nutrient availability (NA) and species evenness on the biomass and nutrient uptake patterns of assemblages formed by Lolium perenne, Plantago lanceolata and Holcus lanatus. When the nutrients were heterogeneously supplied, assemblages exhibited precise root foraging patterns, and had higher above- and belowground biomass (average increases of 32% and 29% for above- and belowground biomass, respectively). Nutrient heterogeneity also modulated the effects of NA on biomass production, complementarity in nitrogen uptake and below: aboveground ratio, as well as those of [CO2] on the nutrient use efficiency at the assemblage level. Our results show that nutrient heterogeneity has the potential to influence the response of plant assemblages to simultaneous changes in [CO2], nutrient availability and biotic diversity, and suggest that it is an important environmental factor to interpret and assess plant assemblage responses to global change. [ABSTRACT FROM AUTHOR]

Decreased arsenate [As(V)] uptake is the major mechanism of naturally selected As(V) hypertolerance in plants. However, As(V)-hypertolerant ecotypes also show enhanced rates of phytochelatin (PC) accumulation, suggesting that improved sequestration might additionally contribute to the hypertolerance phenotype. Here, we show that enhanced PC-based sequestration in As(V)-hypertolerant Holcus lanatus is not due to an enhanced capacity for PC synthesis as such, but to increased As(V) reductase activity. Vacuolar transport of arsenite -thiol complexes was equal in both ecotypes. Based on homology with the yeast As(V) reductase, Acr2p, we identified a Cdc25-like plant candidate, HlAsr , and confirmed the As(V) reductase activity of both HlAsr and the homologous protein from Arabidopsis thaliana. The gene appeared to be As(V)-inducible and its expression was enhanced in the As(V)-hypertolerant H. lanatus ecotype, compared with the non-tolerant ecotype. Homologous ectopic overexpression of the At ASR cDNA in A. thaliana produced a dual phenotype. It improved tolerance to mildly toxic levels of As(V) exposure, but caused hypersensitivity to more toxic levels. Arabidopsis asr T-DNA mutants showed increased As(V) sensitivity at low exposure levels and enhanced arsenic retention in the root. It is argued that, next to decreased uptake, enhanced expression of Hl ASR might act as an additional determinant of As(V) hypertolerance and As transport in H. lanatus. [ABSTRACT FROM AUTHOR]

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 withLolium perenneandHolcus 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. [ABSTRACT FROM AUTHOR]

We have developed a method to extract and separate phytochelatins (PCs)—metal(loid) complexes using parallel metal(loid)-specific (inductively coupled plasma-mass spectrometry) and organic-specific (electrospray ionization-mass spectrometry) detection systems—and use it here to ascertain the nature of arsenic (As)-PC complexes in plant extracts. This study is the first unequivocal report, to our knowledge, of PC complex coordination chemistry in plant extracts for any metal or metalloid ion. The As-tolerant grass Holcus lanatus and the As hyperaccumulator Pteris cretica were used as model plants. In an in vitro experiment using a mixture of reduced glutathione (GS), PC2, and PC3, As preferred the formation of the arsenite [As(III)]-PC3 complex over GS-As(III)-PC2, As(III)-(GS)3, As(III)-PC2, or As(III)-(PC2)2 (GS: glutathione bound to arsenic via sulphur of cysteine). In H. lanatus, the As(III)-PC3 complex was the dominant complex, although reduced glutathione, PC2, and PC3 were found in the extract. P. cretica only synthesizes PC2 and forms dominantly the GS-As(III)-PC2 complex. This is the first evidence, to our knowledge, for the existence of mixed glutathione-PC-metal(loid) complexes in plant tissues or in vitro. In both plant species, As is dominantly in non-bound inorganic forms, with 13% being present in PC complexes for H. lanatus and 1% in P. cretica. [ABSTRACT FROM AUTHOR]

The effect of competition and artificially created soil heterogeneity was studied in a pot experiment. A tussock grass, Holcus lanatus, and the rhizomatous sedge Carex hartmanii were grown alone and in combination with another tussock grass, Molinia caerulea, in homogeneous and heterogeneous soil treatments. The heterogeneous treatment consisted of four compartments, two nutrient rich and two nutrient poor. In the homogenous treatment total nutrient content was the same as in the heterogeneous treatment. Soil heterogeneity increased M. caerulea total production, and increased C. hartmanii root:shoot ratio; no effect on H. lanatus was observed. Both M. caerulea and C. hartmanii were able to place their underground organs preferentially into nutrient rich patches. M. caerulea and H. lanatus total biomass was lower in the presence of the competitor; C. hartmanii responded to competition only by increased allocation to rhizoms. M. caerulea was more affected by competition in the heterogeneous environment [ABSTRACT FROM AUTHOR]

Discusses the distribution of arsenate and arsenite in shoots and roots of holcus lanatus. Role of phytochelatins in the arsenic detoxification in terrestrial plants; Metabolism of arsenic in plant material; Use of high-performance liquid chromatography-inductively coupled plasma mass spectrometry.

Summary 1 We examined the effects of plant-feeding nematodes on competition between Holcus lanatus and Anthoxanthum odoratum . In the Drentse A nature reserve, the Netherlands, a relatively productive grassland, represented by H. lanatus , has gradually been replaced by a less-productive community, represented by A. odoratum , after the application of fertiliser was stopped. Stressed plants are generally considered to be more sensitive to herbivory. 2 We hypothesized that plant-feeding nematodes would exacerbate the competitive disadvantage of H. lanatus resulting from nutrient limitation. We compared performance in an adjusted De Wit replacement series with monocultures, grown in soil that was either treated or untreated with nematicides at both low and high nutrient supply. 3 The biomass production of both plant species was negatively affected by intra- and interspecific competition. Although H. lanatus was a stronger competitor than A. odoratum in mixed cultures, it was more sensitive to plant-feeding nematodes and nutrient limitation. Nematodes and nutrient stress therefore reduced the competitive suppression of A. odoratum by H. lanatus . Low nutrient availability did not enhance the effect of plant-feeding nematodes on plant growth and competition, indicating additive rather than synergistic effects on plant performance. 4 We conclude that plant-feeding nematodes may contribute to species replacements in grasslands after fertilization has been stopped, albeit to a lesser extent than reduced nutrient availability. Plant species-specific differences in tolerance to plant-feeding nematodes in general, rather than host specificity of nematodes, are responsible for any effects. [ABSTRACT FROM AUTHOR]

Summary • The role of arbuscular mycorrhizal fungi (AMF) in arsenate resistance in arbuscular mycorrhizal associations is investigated here for two Glomus spp. isolated from the arsenate-resistant grass Holcus lanatus . • Glomus mosseae and Glomus caledonium were isolated from H. lanatus growing on an arsenic-contaminated mine-spoil soil. The arsenate resistance of spores was compared with nonmine isolates using a germination assay. Short-term arsenate influx into roots and long-term plant accumulation of arsenic by plants were also investigated in uninfected arsenate resistant and nonresistant plants and in plants infected with mine and nonmine AMF. • Mine AMF isolates were arsenate resistant compared with nonmine isolates. Resistant and nonresistant G. mosseae both suppressed high-affinity arsenate/phosphate transport into the roots of both resistant and nonresistant H. lanatus . Resistant AMF colonization of resistant H. lanatus growing in contaminated mine spoil reduced arsenate uptake by the host. • We conclude that AMF have evolved arsenate resistance, and conferred enhanced resistance on H. lanatus. [ABSTRACT FROM AUTHOR]

Summary 1 The long-term benefits of root foraging in heterogeneous environments are unclear. The short duration of many previous studies may have overlooked the effects of patch depletion and root turnover, which may limit the long-term rewards of root foraging for perennial plants. 2 The benefits of root foraging were investigated for Holcus lanatus and Nardus stricta over two growing seasons. Shoot biomass of each species was measured in homogeneous nutrient-rich and nutrient-poor treatments and in a heterogeneous treatment consisting of a nutrient-rich and a nutrient-poor side, at a high and a low overall level of nutrient availability at the same patch contrast. Large initial differences in nitrate concentrations in the soil solution between the soil types disappeared so that, after several months, nitrate levels were low in all soil types. 3 In heterogeneous treatments, Holcus was able to proliferate roots in the nutrient-rich side compared with the nutrient-poor side, but only at the high overall level of nutrient availability. Nardus did not selectively place roots in the nutrient-rich side of the heterogeneous treatment at either nutrient level. 4 Root longevity, as determined by minirhizotron observations, revealed that roots of Holcus tended to be shorter lived than those of Nardus , and to live longer in nutrient-poor soils. 5 Initially, Holcus produced more shoot biomass in the heterogeneous treatments, at both overall levels of nutrient availability, than expected from values in the homogeneous treatments, but this advantage disappeared by the end of the first growing season and, after 2 years, shoot biomass in the heterogeneous treatments was much less than expected. At the high overall level of nutrient availability, Holcus shoot biomass was not significantly greater than that produced in the homogeneous nutrient-poor treatment. In contrast, shoot biomass of Nardus in the heterogeneous treatment was similar to the expected value, both after the... [ABSTRACT FROM AUTHOR]

Abstract The biochemical responses of Holcus lanatus L. to copper and arsenate exposure were investigated in arsenate-tolerant and -non-tolerant plants from uncontaminated and arsenic/copper-contaminated sites. Increases in lipid peroxidation, superoxide dismutase (SOD) activity and phytochelatin (PC) production were correlated with increasing copper and arsenate exposure. In addition, significant differences in biochemical responses were observed between arsenate-tolerant and -non-tolerant plants. Copper and arsenate exposure led to the production of reactive oxygen species, resulting in significant lipid peroxidation in non-tolerant plants. However, SOD activity was suppressed upon metal exposure, possibly due to interference with metallo-enzymes. It was concluded that in non-tolerant plants, rapid arsenate influx resulted in PC production, glutathione depletion and lipid peroxidation. This process would also occur in tolerant plants, but by decreasing the rate of influx, they were able to maintain their constitutive functions, detoxify the metals though PC production and quench reactive oxygen species by SOD activity. [ABSTRACT FROM AUTHOR]

In normal populations of the common grass Holcus lanatus there is a polymorphism for arsenite resistance, manifested as suppressed phosphate uptake (SPU), and controlled by a major gene with dominant expression. A natural population of SPU plants had greater arbuscular mycorrhizal colonization than wild type, non SPU plants. It was hypothesized that, in order to survive alongside plants with a normal rate of phosphate (P) uptake, SPU plants would be more dependent on mycorrhizal associations. We performed an experiment using plants with SPU phenotypes from both arsenate mine spoils and uncontaminated soils, as well as plants with a nonSPU phenotype. They were grown with and without a mycorrhizal inoculm and added N, which altered plant P requirements. We showed that grasses with SPU phenotypes accumulated more shoot P than non SPU plants, the opposite of the expected result. SPU phenotypes in normal populations is not necessarily related to mycorrhizal colonization as there were no differences in percentage AM colonization between the phenotypes. Being mycorrhizal reduced flower biomass production, as mycorrhizal SPU plants had lower shoot P concentrations and produced fewer flower panicles than non-mycorrhizal, nonSPU plants. We now hypothesize that the SPU phenotype is brought about by a genotype that result in increased accumulation of P in shoots, and that suppression of the rate of uptake is a consequence of this high shoot P concentration, operating by means of a homeostatic feedback mechanism. We also postulate that increased flower production is linked to a high shoot P concentration. SPU plants thus allocate more resources into seed production, leading to a higher frequency of SPU genes. Increased reproductive allocation reduced vegetative allocation and may affect competitive ability and hence survival, explaining the maintenance of the polymorphism. As mycorrhizal SPU plants behave more like nonSPU plants. AM colonization itself could play a major part in the maintenance of the SPU polymorphism. [ABSTRACT FROM AUTHOR]

Describes the influence of arbuscular mycorrhizal infection on competition between Holcus lanatus and Dactylis glomerata. Comparison between monocultures and mixtures; Implications of increased shoot biomass; Calculating relative yield totals.

Describes two glasshouse bioassays using field soil which were designed to test for effects of removal experiment methodology on plant growth. Experiment on Holcus lanatus plants; Mycorrhizal infection of Holcus lanatus roots; Effects of the disturbance resulting from total plant removal.

Investigates the effect of clipping on the outcome of interclonal competition in the Holcus lanatus grass. Use of response surface analysis; Effect of clipping treatment and the relative densities of competing clonal grasses; Role of environmental heterogeneity in the outcome of intergenotypic competition.

1. Species in plant communities generally shown an aggregated distribution at one or more spatial scales. This, and the fact that competition between sessile organisms occurs chiefly between neighbours, suggests that the spatial configuration of plants should affect the process and outcome of interspecific competition. 2. Cellular automaton models were constructed to simulate the competitive interaction of five grass species. Agrostis stolonifera, Holcus lanatus, Cynosurus cristatus, Poa trivialis and Lolium perenne, based on experimentally determined rates of invasion. 3. A model with a random initial starting arrangement showed a very rapid loss of species compared to initial arrangements in which species occurred in monospecific bands. 4. Different arrangements of monospecific bands produced quite different results from each other, depending only upon the initial juxtaposition of species in the model community. Non-linear dynamics, with transitory increases followed by decreases in species' abundance, were observed with some starting arrangements. Community change followed trajectories that could not be deduced in any simple manner from a knowledge of pairwise interactions alone. These results suggest that the spatial pattern and configuration of competing species may be just as important as the density and frequency of competitors in determining the outcome. [ABSTRACT FROM AUTHOR]

(1) This study assessed the relative contributions of plant genotype and two environmental variables to phenotypic variability in demographic traits within adjacent populalions of the perennial grass Holeus lanatus Replicated clones were established in six simulated introductions, or cohorts, in a a reciprocal-transplant experiment (2) In the 'impoved' population, when clonal replicates were transplanted back into their field of origin, survival to reproduction and survival over the two years of the experiment had no significant genetic components of variation In the 'traditional' poputation, in its field of origin, varianon in survival to reproduction had a genetic component of 47%, and survival to the end of the experiment had a generic component of 16%. Because the total phenotypic variances were not different, this suggests that the first populalation had greater phenotype plasticity Variation in number of inflorescences produced by each transplant had a genetic componcnt of 9% in the improved population and 45% in the traditional population. (3) Genotype-environment interaction effects resulted in different relative contributions of genetic and environmental effects when the same traits were measured in the alien field. In all cases variation due to the environment, or phenotypic plasticity, was greater than the genetic variation plus phenotypic carry-over effects. (4) There was no evidence to suggest that clonal transplants had greater vegatative survival in their home fields. For the reproductive character measured (the number of inflorescences per transplant, however, two clones from the traditional populations produced more inflorescenecs in their field of origin; the number of seeds per inflorescence did not vary No evidence for a trade-off between reproduction and survival over the twoyear experiment was found. (5) Repeating the reciprocal-transplant experiment at bye-week intervals showed that time of transplanting significandly... [ABSTRACT FROM AUTHOR]

(1) The growth of three grasses whose natural distribution ranged from acidic to calcareous soils was measured in response to the concentration of two major pH-linked soil chemical factors, nitrogen and aluminium, supplied in flowing culture. (2) All three species showed one or more of the basic responses proposed in four hypotheses based on their ecological distribution. (3) Deschampsia Jlexuosa grew equally fast with either NO3-N or NH4 N as the nitrogen source. It was tolerant of any combination of N source and aluminium except for the highest concentration of Al (5.4 mg 1-1) supplied with NO3 N. (4) Holcus lanatus grew significantly faster in NO3 N than it did in NH4N and showed classical symptoms of aluminium toxicity in the presence of NO3-N. The strongly adverse effect of NH4- N was significantly ameliorated by the addition of aluminium. (5) Bromus erectus also grew significantly faster in NO3-N than it did in NH4-N and was susceptible to aluminium toxicity in the presence of NO3-N. The very small extent of growth in NH4-N masked any possible effects of aluminium and growth was not increased in the presence of aluminium. (6) A revision of ideas on the roles of inorganic toxins in acidic soils is proposed. [ABSTRACT FROM AUTHOR]

Plots of rough grassland dominated by Holcus lanatus L. were cleared of vegetation in three successive years and allowed to regenerate without grazing or harvesting. Vegetation cover and foliar disease severity were measured using pin sampling in each plot, two to four times per year. One third of plots were sprayed regularly with propiconazole to reduce fungal disease; one third of plots were sprayed with rust (Puccinia coronata f. sp. holci Corda.) urediospores in the second and third years of the study and with conidia of the leaf-spotting fungus Ascochyta leptospora (Trail) Hara. in the third year. The fungicide had direct effects on the growth of perennial herbs and grasses, and indirect effects through disease control on perennial herbs. Both fungicide treatment and disease augmentation tended to raise diversity in plots where grasses were only partly dominant. Fungicides increased diversity because both direct and indirect effects were greater in perennial herbs than in grasses. Disease augmentation raised diversity because the diseases introduced were more specific to the most common component of the vegetation, H. lanatus. [ABSTRACT FROM AUTHOR]

The effects of clipping and daylength treatments and their carryover effects on the clonal growth of the perennial grass Holcus lanatus L. were investigated. Plants from ten clones were grown in six combinations of two daylength and three clipping treatments. Both clipping and low daylength reduced the tillering rate of all the clones but the clones differed in their degree of response to these treatments. After eight weeks, the treatments were discontinued and plants were grown in a common environment for seven weeks. Four-week-old tillers from the plants were repotted and grown in a common environment to examine the possibility of `carryover' effects of the parental environments. After 8 wk of growth, there were main and interaction carryover effects of daylength and clipping on the tillering rates, biomass and tiller extension rates of the plants, which, however, differed greatly among clones. These differences among clones in both direct and carryover treatment effects, on clonal growth, indicate how the effects of many different environmental variables may interact to produce an environment that is highly heterogeneous in space and time, influencing the coexistence of genotypes and species. [ABSTRACT FROM AUTHOR]

Arsenate influx isotherms in Deschampsia cespitosa (L.) Bieauv. and Agrostis capillaris L. showed that tolerance to arsenate in these grasses is achieved at least in pan by adaptation of the arsenate uptake system, which leads to reduced influx of arsenate in arsenate-tolerant plants. In D. cespitosa this reduction in arsenate influx was by suppression of the Vmax the high-affinity uptake system and by an increase in the Km of the low-affinity uptake system. In A. capillaris the reduction in arsenate uptake in arsenate-tolerant plants was by a decrease in the Vmax of both uptake systems and by an increase in the Km of the high-affinity uptake system. The differences in the rates of arsenate influx between tolerant and non-tolerant plants was much greater for D. capillaris than for A. capillaris. The mechanism of arsenate tolerance in D. cespitasa and A. capillaris was the same mechanism of tolerance that had been demonstrated in arsenate-tolerant Holcus lanatus L. Reduced arsenate influx by adaptation of the arsenate uptake mechanism is a mechanism of tolerance that has evolved in three separate species. [ABSTRACT FROM AUTHOR]

Uptake, translocation and accumulation of arsenate was determined in arsenate-tolerant and non-tolerant genotypes of Holcus lanatus L. Over a 6 h period of growth in 0.05 mol m-3 a arsenate, non-tolerant genotypes accumulated arsenate to a much greater extent than tolerant plants. Tolerant plants transported a much greater proportion of As to then shoots compared with non-tolerant plants. Phosphate at a concentration of either 0.05 or 0.5 mol m-3 decreased arsenate uptake in both tolerant and non-tolerant genotypes. When arsenate uptake was determined over 3 d at the same arsenate concentration, non-tolerant plants grown in the presence of 0 and 0.05 mol m-3 phosphate died, while those growing in 0.5 mol m-3 phosphate survived and continued to take up arsenate. At all three phosphate levels tolerant plants survived. Over the 3 d period transport of arsenate to the shoots decreased. With increasing phosphate levels in solution transport of arsenate to the shoots increased in tolerant plants. The results from these experiments are discussed in terms of strategies for metal tolerance in this species. [ABSTRACT FROM AUTHOR]

The mechanism of phosphate and arsenate uptake was investigated in arsenate-tolerant and non-tolerant genotypes of Holcus lanatus L. It appeared that arsenate and phosphate were taken up by the roots by the same uptake system in both genotypes, although the uptake system had a much greater affinity for phosphate than arsenate. In non-tolerant plants the uptake of both anions was much greater than for tolerant plants at low phosphate and arsenate concentrations. High-affinity uptake appeared to be absent in the tolerant plants for both arsenate and phosphate. The absence of this high-affinity uptake is discussed in terms of arsenate tolerance in this species. The identification of a mutant with only one phosphate uptake system provides further evidence that 'normal' uptake of ions occurs via two distinct transport systems. The theoretical and ecological implications of this altered phosphate uptake mechanism are considered. [ABSTRACT FROM AUTHOR]

To examine the ecological relevance of slow growth for survival in unproductive environments, responses to nutrient depletion were compared between two ecologically contrasted grasses with reference to their ability to utilize a nutrient flush. Dry weight growth, ability of roots to absorb nitrogen and subsequent distribution between root and shoot were determined for Holcus lanatus L. and Festuca ovina L. before and after subjecting them to nutrient depletion at warm and cool temperatures. Initially, the relative growth rates (RGR) of H. lanatus were much higher than those of F. ovina, but after 21 days of nutrient depletion, F. ovina attained higher RGR. During nutrient depletion, F. ovina maintained higher shoot N concentrations than H. lanatus, mainly due to lower rates of dry matter accumulation in F. ovina. Maintenance of N concentrations in F. ovina may contribute to sustaining of the shoot activity under N-depleted conditions. Nutrient depletion caused an increase in the proportion of N allocated to roots relative to shoots, but F. ovina exhibited less plasticity than H. lanatus. Following nutrient depletion, the ability of roots to absorb nitrate declined markedly in H. lanatus and to a much lesser extent in F. ovina. The ability to absorb ammonium was also reduced at warm temperatures, while at cool temperatures it was unchanged in H. lanatus, but increased in F. ovina. These results suggest that F. ovina has a greater potential to exploit 'nutrient flushes' than H. lanatus under unproductive conditions, especially at cool temperatures. [ABSTRACT FROM AUTHOR]

After 7 weeks' growth in varying NaCI concentrations in sand culture, dry matter production and tiller number were compared for the progenies of NaCI-tolerant selection lines and the progenies of unselected control lines of Holcus lanatus L., Lolium perenne L., Dactylis glomerata L. and Festuca rubra L. The tolerant lines had been produced by selection at the seedling stage. In each species, selected lines produced significantly more dry matter and had greater tiller numbers than unselected material, particularly at high levels of NaCI. Shoot/root ratios differed Significantly only in L. perenne, unselected material having a higher shoot/root ratio. These data confirm that for these four species, selection based upon differences in seedling root growth is a valid means of selecting for improved NaCI tolerance in adult plants, and that this tolerance does not lead to any reduced performance in the absence of NaCl. [ABSTRACT FROM AUTHOR]

Holcus lanatus is the dominant grass over large areas of thin peat soil on the western sea-cliffs of Lundy Island, exposed to salt spray. Its tolerance of artificial sea water (ASW) on peat or loam soils when grown alone or in mixture with either an agricultural cultivar of H. lanatus, Massey Basyn or with `Aberystwyth S. 23' Lolium perenne was investigated. Under salt spray, on peat soil, `Lundy' H. lanatus had the highest tiltering ability and, unlike the others, its yield was unaffected by the spray. When high levels of salt were applied to the soil, the yield of L. perenne was lowest when it was grown on peat and was also in competition with `Lundy' H. lanatus. On peat soil, the agricultural cultivar of H. lanatus was more productive than L. perenne. It was also at least as productive as `Lundy' H. lanatus when grown on peat with a high level of salt in the soil solution. When immersed in a solution of ASW, the leaves of L. perenne retained approximately 17 times more salt than did those of either `Lundy' or `Massey' H. lanatus. There was no evidence for sodium ions being adsorbed on to the cuticle of any of the grasses. `Seeds' of both L. perenne and `Massey' H. lanatus germinated readily in 40% ASW. However, germination of `Lundy' H. lanatus `seeds' was much reduced at this salt level, especially from intact spikelets, although they germinated readily when transferred to fresh water. The establishment of `Lundy' H. lanatus under 120 kg ha&sup-1; day' of sea-salt was slower than that of the other two grasses. [ABSTRACT FROM AUTHOR]

Three grasses were grown in a split-root solution culture experiment in which only a fraction of the root system of each plant was supplied with 4.0 mol m&sup-3; N as NH4NO3. The solutions were labelled with 15NO2 or 15NH4 during the final 24 h of the experiment. Deschampsia flexuosa, unlike Holcus lanatus and Lolium perenne, showed no reduction in total dry weight production relative to the controls. Proportionately greater increases in specific N-absorption rate were measured in D. flexuosa compared with H. lanatus and L. perenne. All three species exhibited large changes in root morphology (length: dry weight). In D.flexuosa such changes were confined only to those roots having direct access to N (+ N roots); in H. lanatus and L. perenne this response occurred also in the rest of the root system (-N roots). The proportion of 15N transported to the - N roots was greater in H. lanatus and L. perenne. Increased transport of ammonium-N to the shoot was found in D. flexuosa and, it is suggested, this stabilized the root: shoot ratio and maintained maximum relative growth rate. The smaller absolute N demand of D. flexuosa was such that responses to maximize N uptake, to confine to a greater extent the utilization of N to + N roots, and to maintain N supply to the shoot, ensured full compensation for the restricted N supply. The inherently higher N demands of H. lanatus and L. perenne could not be met by increases in specific absorption rates. In addition, the transport of relatively greater amounts of 15N to -N roots rather than to the shoot, and the consequent increase in root:shoot ratios prevented compensation from being achieved to the same extent. Thus, the efficient utilization of dry matter and nutrient resources appear to be important factors enabling D. flexuosa to grow effectively under restricted conditions of nutrient supply. [ABSTRACT FROM AUTHOR]

Both Bromus erectus and Holcus lanatus grew better in NO3-N than in NH4-N. NH4-N inhibited Mn uptake and NO3-N enhanced it. The concentration of Mn found in both species was greater in NO3-N than NO4-N treated plants and increased severity of toxicity symptoms was observed in plants given NO3-N treatments. In general, uptake and concentration of Mn was greater in Holcus than in Bromus, although Holcus displayed less severe symptoms of toxicity. Root concentrations of Mn were greater than those of shoots in Holcus. As excess Mn generally affects plant tops more severely than roots it is possible that a mechanism reducing upward translocation of Mn conferred a degree of tolerance in Holcus. Growth of the population of Holcus used was affected to a lesser extent than Bromus by large concentrations of Mn in nutrient solution which may partially account for the markedly different frequency of occurrence of these species on soils which contain high concentrations of both NO4-N and Mn. In Bromus NO4-N and Mn interact to reduce their combined effects but in both species the adverse effects of NO4-N on growth for the most part masks that of Mn. Conversely with NO3-N, itself beneficial, Mn uptake is not depressed as it is with NO4-N and when Mn-toxicity occurs, it is more marked. In solution culture Bromus is very sensitive to NO4-N and also to Mn in the presence of NO4-N or NO3-N, whereas in the kind of habitat in which Bromus occurs N is present as NO3 and the adverse effect of any Mn present is neutralized by Ca. [ABSTRACT FROM AUTHOR]

A cadmium tolerant and a non-tolerant population of Holcus lanatus were subjected to a pretreatment with either no or low (0.2 μg ml-1) concentrations of cadmium prior to normal tolerance testing in 1.0 μg Cd ml-1 solution. When pretreated roots were not removed prior to the tolerance test, the cadmium pretreatment resulted in significantly greater root growth of both populations in the test solution relative to plants given no cadmium pretreatment. Repeating the tolerance test on plants which had their pretreated roots excised prior to testing showed no significant effect of any pretreatment on subsequent root growth in either population. There was an overall difference between the two populations in terms of their response to pretreatment and test concentrations in that when exposed to cadmium, plants of the tolerant population grew significantly better than those of the non-tolerant population. The data presented provide evidence for a stimulation of cadmium tolerance following low-level exposure of roots to cadmium. The mechanisms associated with these effects are not clear although cadmium tolerance in animals is known to show similar trends. [ABSTRACT FROM AUTHOR]

The tolerance of Holcus lanatus to lead, zinc and cadmium alone and in combination was studied in a factorial experiment. Cadmium/zinc, lead/cadmium and lead/cadmium/zinc interactions, as measured by their effect on root growth, occurred but were not consistent between the two populations. The population from a contaminated site showed a distinct tolerance to lead, zinc and cadmium in combination, compared to the non-tolerant population. These results are discussed in relation to the literature of heavy metal tolerance and metal effects on plants. [ABSTRACT FROM AUTHOR]

Holcus lanatus, collected 2.8 km from a large smelting complex, exhibited distinct tolerance to cadmium. Tolerant plants grew less well on normal culture solution than non-tolerant plants but grew roots at normal rates in the presence of concentrations of cadmium related to those present in the field. These results are discussed in relation to the previous literature of metal tolerance and reference is made to the problems associated with the quantitative measurement of tolerance. [ABSTRACT FROM AUTHOR]

Group V grass pollen allergens belong to the major grass pollen allergens causing reactions of type I allergy. cDNAs coding for two isoforms of the group V allergen of velvet grass pollen (Holcus lanatus), a widespread grass species, were isolated from a cDNA library by hybridization with a 5′-terminal reverse-transcribed PCR-derived cDNA probe. Amino acid sequences of the two isoforms, designated rHol l 5.01 and rHol l 5.02, revealed high similarity between them (78 % identity) and to group V allergens and their isoforms found in other grass species. Recombinant Hol l 5 isoforms were expressed in Escherichia coli and purified as fusion proteins. To compare their immunological reactivities with group-V-specific monoclonal antibodies and patients' IgE, immunoblotting, ELISA and histamine release assay were performed. Interestingly, monoclonal antibody Bo9, specific for group Vb isoforms of timothy grass, bound only to isoform rHol l 5.01, not to rHol l 5.02. On the other side, IgE reactivities of patients' sera revealed no differences between the two isoforms when investigated by immunoblotting and only slight differences when investigated by ELISA. In histamine release assay both isoforms released comparable amounts of histamine from basophils of four individual patients. Thus, the two group V isoforms of velvet grass pollen exhibit differential binding when tested with monoclonal antibodies, i.e. different structure of single epitopes, but negligible differences concerning overall IgE-binding capacity and histamine-releasing capacity. [ABSTRACT FROM AUTHOR]

(1) Plants of Holcus lanatus L. and Lolium perenne L. were grown in monocultures and in 50:50 mixture in free-draining conditions and with the water table at 5, I 1 or 21 cm below the soil surface. (2) The shoot dry weight and nitrogen contem (%) of both species declined similarly with increasing height of water table, in both monocultues and mixtures. (3) However, only H. lanatus responded to the high water table by producing large numbers of nodal roots and fine surface roots which may enable it to survive better in such conditions. [ABSTRACT FROM AUTHOR]