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The vegetation of the embankments of the Zak van Zuid-Beveland were surveyed phytosociologically, the vegetation being assigned to the Lolio-Cynosuretum plantaginetosum mediae, Arrhenatheretum elatioris picridetosum, Arrhenatheretum elatioris alopecuretosum and Ulmo-Rubetum ulmifolii . In total, including the subordinate fragmentary communities and variants, 12 communities are described, together with an indication of their synecology. The composition of the vegetation in 1986 is compared to that in 1972 and the influence of different management practices, i.e. grazing, mowing, burning and no management, on the vegetation changes is illustrated. The changes in vegetation composition and structure are clearly related to management practices. This even applies to the low level of syntaxonomic hierarchy, i.e. subassociations and variants. In general the highest intensities of grazing by the flock, i.e. between 8 and more than 15 h a month by 200 sheep per 500 m of embankment, were best suited for the improvement or maintenance of the conservation value. Under the same conditions, light grazing (less than 8 hours) proved to be insufficient.

International audience; Free-living nitrogen (N) fixation can be important for sustainable soil fertility, particularly in extensively managed soils with low abundance of leguminous plant species. However, the factors affecting free N-2-fixation in situ are still poorly documented. We investigated the role of microbial active biomass activity, particularly substrate-induced respiration (SIR) and net N mineralization, on the free-living N-2 fixation in soils under a semi-natural grassland ecosystem in France. Analysis of replicated bulk soil and rhizospheric soil samples obtained from sites experiencing contrasting grazing regimes revealed highly significant negative relationships (P < 0.01) between free-living N-2-fixation and SIR or N-mineralization with a significant rhizosphere effect. The study has demonstrated that the activity of free-living N-2-fixers is more important in soils having low active microbial biomass and low N-mineralization rates in these permanent grasslands.

Several studies have shown that the contribution of individual species to the positive relationship between species richness and community biomass production cannot be easily predicted from species monocultures. Here, we used a biodiversity experiment with a pool of nine potentially dominant grassland species to relate the species richness–productivity relationship to responses in density, size and aboveground allocation patterns of individual species. Aboveground community biomass increased strongly with the transition from monocultures to two-species mixtures but only slightly with the transition from two- to nine-species mixtures. Tripartite partitioning showed that the strong increase shown by the former was due to trait-independent complementarity effects, while the slight increase shown by the latter was due to dominance effects. Trait-dependent complementarity effects depended on species composition. Relative yield total (RYT) was greater than 1 (RYT > 1) in mixtures but did not increase with species richness, which is consistent with the constant complementarity effect. The relative yield (RY) of only one species, Arrhenatherum elatius, continually increased with species richness, while those of the other species studied decreased with species richness or varied among different species compositions within richness levels. High observed/expected RYs (RYo/RYe > 1) of individual species were mainly due to increased module densities, whereas low observed/expected RYs (RYo/RYe < 1) were due to more pronounced decreases in module density (species with stoloniferous or creeping growth) or module size (species with clearly-defined plant individuals). The trade-off between module density and size, typical for plant populations under the law of constant final yield, was compensated among species. The positive trait-independent complementarity effect could be explained by an increase in community module density, which reached a maximum at low species richness. In contrast, the increasing dominance effect was attributable to the species-specific ability, in particular that of A. elatius, to increase module size, while intrinsic growth limitations led to a suppression of the remaining species in many mixtures.

The purpose of this study was to investigate, under standard conditions, the bioaccumulation of zinc and cadmium in Arrhenatherum elatius, a perennial grass with a high biomass production. Nine populations of three different origins were tested: three metallicolous populations (mpop); three non-metallicolous populations (nmpop) and three populations developing on soils moderately metal polluted (medpop). We have found that bioaccumulation differs among these populations, with nmpop accumulating significantly more zinc (p0.0001) and cadmium (p0.0001) than mpop. Indeed, we have observed a concentration of 325 mg kg(-1) of zinc and 52 mg kg(-1) of cadmium in A. elatius shoots from mpop, whereas in nmpop, the concentration reached on average 524 mg kg(-1) zinc and 83 mg kg(-1) cadmium. In the same way, medpop accumulated as much zinc but more cadmium than nmpop. Moreover, the standard deviation of medpop was larger than the one for mpop and nmpop. Indeed, some A. elatius samples from medpop presented a high metal content whereas, others presented low concentrations in their shoots (ranging from 60 to 210 mg kg(-1) cadmium). Hence, these medpop exhibited a large variability among and within populations in accumulating zinc and cadmium in their shoots. Based on these results, the possibility of selecting A. elatius plants with the best accumulating capacity from medpop was proposed. We concluded that if the accumulation capacity is genetically controlled in A. elatius, this species fulfils this necessary condition for efficiently increasing species bioaccumulation by crossbreeding A. elatius plants with the higher accumulation capacity.

International audience; Theoretical models predict that the net outcome of biotic interactions among plants is the sum of co-occurring negative and positive interactions, with facilitation generally increasing in importance with increasing abiotic stress. However, species differ in fundamental niche optima; thus the intensity of stress is relative among species and important only in the context of these relative differences. We tested the hypothesis that the facilitative response of a species is relative to how much abiotic conditions deviate from the optimum conditions for that particular species (stress), and the competitive "response" ability of the species (i.e., its ability to tolerate the inhibitory effects of neighbors). In a field experiment, we examined the responses of three co-occurring species with different ecological optima, Bromus erectus, Brachypodium rupestre, and Arrhenatherum elatius, to the alleviation of a primary limiting resource (water), and to biotic interactions in a mesoxeric grassland in eastern France. We found that A. elatius had a strong positive response to watering, the response of B. rupestre was moderately positive, and B. erectus did not respond significantly, suggesting that water stress was only important for the first two species. Most importantly, the net outcome of the interaction between each species and its neighbors depended on the degree of water stress it experienced in its natural habitat. For survival, in the control plots we found no significant interactions for B. erectus (not stressed) whereas B. rupestre and A. elatius (stressed species) were facilitated. Enhancing water availability suppressed facilitation of B. rupestre and A. elatius and led to competitive exclusion of B. erectus. In contrast to survival, there was no facilitation for growth in the control plots, and competition intensity increased for all three species with watering. In our experiment the competitive response of a species was inverse to its ability to tolerate stress, indicating a trade-off between these components of the species response. A facilitative outcome appears to be a function of a species having both a low tolerance to a particular abiotic stress and a strong competitive-response ability.

Summary 1 Summer floods whose severity is affected by flooding duration, submergence depth and underwater light availability, have a large impact on the zonation of riparian plant species. 2 We analysed the range and variability of these flooding components in the River Rhine and quantified their effects on the ability of Arrhenatherum elatius, Achillea millefolium, Rumex acetosa and Rumex crispus, to survive periods of submergence under experimental conditions. 3 Survival characteristics were used to model species’ lower distribution boundaries for extreme and average floods and were compared with the current field distribution. Different light conditions were simulated by implementing three scenarios of suspended load. 4 Extreme deep Rhine floods are characterized by very low median light transmission levels (i.e. below 0.5%). The largest survival responses in the experiment were observed at such low levels (0.4–3.5 µmol m−2 s−1). Strong effects of light were found in R. crispus and A. millefolium, but responses were weaker in A. elatius and R. acetosa. Submergence depth also affected survival, but not as strongly as light. 5 For the flood intolerant species (A. millefolium and A. elatius) the average flood was predicted to have little effect on field distributions under normal light conditions. However, their actual field distributions in 2000 corresponded to the predicted lower boundaries in the extreme years. This suggests that extreme years determine the distributions of these species for many years. The suspended load scenarios significantly modified the predicted lower boundaries in both extreme and average years, implying that plant lower distribution limits may be significantly shifted upwards or downwards depending on the suspended load of the river system. 6 The predicted lower boundaries of the intermediately tolerant R. acetosa and the highly tolerant R. crispus for both extreme and average years were below the actual field distribution in 2000. This suggests that their current distribution is only partly influenced by major flood disturbances and that other factors, either proximate or historical, may play a prominent role.

Die Emission stickstoffhaltiger Verbindungen aus anthropogenen Quellen hat in den vergangenen Jahrzehnten weltweit stark zugenommen. Stickoxide und Ammoniak tragen hierzu etwa gleichviel bei. Erhöhte Stickstoffdepositionen müssen als wichtigste Ursache für die Eutrophierung vieler Ökosysteme angesehen werden. Besonders bedroht sind Pflanzengesellschaften an nährstoffarmen Standorten wie Halbtrockenrasen. Die Wirkung von gasförmigem Ammoniak wurde bisher vor allem an Nutzpflanzen untersucht, über die Reaktionen von Wildpflanzen liegen vergleichsweise wenige Arbeiten vor. Die Reaktion von Halbtrockenrasen auf gasförmiges NH3 wurde bisher noch nicht untersucht. In dieser Studie wurden mit Bromus erectus (Aufrechte Trespe) und Brachypodium pinnatum (Fieder-Zwenke) zwei in Halbtrockenrasen häufig bestandsbildende Süßgräser als Testpflanzen ausgewählt. Als dritte Art kam mit Arrhenatherum elatius (Glatthafer) ein typisches Gras des Wirtschaftsgrünlandes hinzu, das bei einem erhöhten Stickstoffangebot in Halbtrockenrasen eindringen kann. Die drei Arten wurden über drei Vegetationsperioden einzeln und als Mischkultur in Open Top-Kammern (OTC) erhöhten NH3-Konzentrationen (0 / 20 / 50 µg m-3) und einer veränderten NH4+-Versorgung ausgesetzt (0 / 20 / 50 kg NH4+-N ha-1 a-1) - in allen Kombinationen aus beiden Faktoren. Von jeder Behandlungsvariante existierten vier Töpfe verteilt auf zwei Kammern. Jeweils 12 Pflanzen wuchsen in 18 l-Gefäßen, die mit einem Bodengemisch gefüllt waren, das den Freilandverhältnissen von Halbtrockenrasen nachempfunden war. Die Bewässerung erfolgte mit demineralisiertem Wasser. Die Pflanzen wurden einmal jährlich im Juli / August sieben cm über dem Boden geschnitten. Ein erhöhtes NH3/NH4+-Angebot stimulierte bei allen drei Arten das Sprosswachstum. Die stärksten Steigerungen traten bei Brachypodium auf, bei dem sowohl die Triebdichte als auch die Bestandesblattfläche stark zunahmen. Am geringsten wurde das Wachstum von Bromus gefördert. Während bei Bromus und Brachypodium durch gleichstarke Zuwächse der unterirdischen Biomasse das Wurzel/ Spross-Verhältnis (RSR) stabil blieb, nahm das RSR bei Arrhenatherum unter einem kombinierten NH3/NH4+-Angebot ab. Alle drei Arten steigerten unter erhöhter NH3/NH4+-Versorgung die Wuchshöhe, ebenso verlagerten alle Arten einen Teil ihrer Blattfläche nach oben. Die prozentual stärksten Veränderungen traten bei Brachypodium auf, die geringsten bei Bromus. Dies führte bei Brachypodium und Arrhenatherum zu einer gleichmäßigeren vertikalen Verteilung der Blattfläche, während sich bei Bromus die starke Konzentration in Bodennähe kaum veränderte. Beim Schnitt verloren Arrhenatherum und Brachypodium fast die gesamte Blattfläche, während bei Bromus etwa 1/3 erhalten blieb. Unabhängig von der NH3/NH4+-Versorgung investierten Bromus und Brachypodium mehr in die Blattspreiten als Arrhenatherum. Die höchste Gewebedichte fand sich bei Brachypodium, die niedrigste Spezifische Blattfläche bei Bromus. Die mittlere Lebensdauer der Blattspreiten war bei Bromus und Brachypodium etwa gleich, die Blattspreiten von Arrhenatherum erreichten ein geringeres Alter. In allen vier Mischkulturen stellte Arrhenatherum anfangs den größten Teil der oberirdischen Biomasse. Im Verlauf der Expositionszeit kam es jedoch zu deutlichen Konkurrenzverschiebungen. In Nachbarschaft zu Bromus verlor Arrhenatherum unabhängig vom NHy-Angebot seine dominierende Rolle, in den Kontrollen und beim Angebot einer NHy-Form wurde Bromus selbst zur dominierenden Art. Auch Brachypodium baute seinen Anteil an der Sprosstrockenmasse auf Kosten von Arrhenatherum aus, es wurde in den Kontrollen und unter hohen NH3-Konzentrationen zur beherrschenden Art, bei NH4+-Gaben konnte sich Arrhenatherum jedoch behaupten. Deutliche Schwankungen prägten das Konkurrenzverhältnis zwischen Bromus und Brachypodium, innerhalb der Versuchszeit wurde keine der beiden Arten dominant. Unter den hier gewählten Wuchsbedingungen erwiesen sich Bromus und Brachypodium gegenüber Arrhenatherum als die konkurrenzstärkeren Arten. Als wichtigste Ursache kann die Abnahme des Wurzel/Spross-Verhältnisses bei Arrhenatherum unter einem kombinierten NH3/NH4+-Angebot angesehen werden, die in Verbindung mit den Nährstoffverlusten beim Schnitt und dem hohen Nährstoffbedarf, u.a. aufgrund der kurzen Lebensdauer der gebildeten Organe, sehr wahrscheinlich zu einem mit der Zeit wachsenden Mangel an anderen Nährstoffen außer Stickstoff führte. Arrhenatherum konnte sich auch bei einem erhöhten NH3/NH4+-Angebot nicht auf Kosten der anderen Arten ausbreiten. Daraus lässt sich der Schluss ziehen, dass in regelmäßig genutzten Halbtrockenrasen nur eine geringe Wahrscheinlichkeit besteht, dass stickstoffbedürftigere Arten zunehmen. Zwar war Brachypodium bei Stickstoffmangel Bromus unterlegen, seine Schattenverträglichkeit ermöglichte es Brachypodium jedoch, ein erhöhtes NH3/NH4+-Angebot zu einer massiven Wuchsförderung zu nutzen. Im Freiland führen die sehr dichten Bestände von Brachypodium zu einer Verdrängung von kleinwüchsigen Arten - mit negativen Folgen für die Artenvielfalt in Halbtrockenrasen., The emission of nitrogen-species has increased worldwide dramatically in the past decades. Nitrogen oxides and ammonia contributed equally the same amounts. Elevated nitrogen depositions have to be considered as the most important reason for the eutrophication of many ecosystems. Especially threatened are plant communities at nutrient poor sites such as calcareous grasslands. Till now the effects of ammonia were tested mainly on crop plants, only view studies examined the reactions of wild plants. The reactions of chalk grassland to elevated levels of ammonia have not been tested till now. In this study two typical grasses of calcareous grasslands Bromus erectus (Upright brome) and Brachypodium pinnatum (Heath false-brome) were chosen as test species. The third species was Arrhenatherum elatius (Oat-grass), a typical grass of nutrient rich grassland, that is able to invade chalk grasslands under elevated nitrogen supply. The three species were cultivated in monocultures and mixtures and were exposed over three vegetation periods in Open-top field chambers to three different levels of NH3-concentrations (0 / 20 / 50 µg m-3) and NH4+-fertilization (0 / 20 / 50 kg NH4+-N ha-1 a-1) in all combinations of both factors. Four pots of each treatment were placed in two chambers. 12 plants grew in 18 l-pots, filled with a substrate closely resembling field conditions of poor calcareous grasslands. Demineralized water was used for irrigation. The plants were cut once every year in July / August at a height of seven cm above the soil surface. The shoot-growth of all three species was stimulated by an NH3/NH4+-enrichment. The most intense increases were found with Brachypodium, where both shoot density and canopy leaf area grew intensely. The least responsive species was Bromus. The root/shoot-ratio of Bromus and Brachypodium was unaffected by the NH3/NH4+-supply because of equal increases of above- and belowground biomass, the RSR of Arrhenatherum decreased under a combination of NH3- and NH4+-enrichment. All three species increased their growth height under an elevated NH3/NH4+-supply and shifted a part of their leaf area to higher parts of their shoot. The relatively most striking changes were observed in Brachypodium, the smallest in Bromus. This leads to a more homogenous vertical distribution of the leaf area of Brachypodium and Arrhenatherum, whereas the concentration near the soil was hardly changed for Bromus. With each cutting Arrhenatherum and Brachypodium lost nearly the complete leaf area, whereas by Bromus nearly 1/3 was kept. Independent of the NH3/NH4+-supply Bromus and Brachypodium invested more into their leaf blades than Arrhenatherum. Brachypodium has the highest tissue density, the smallest specific leaf area was found in Bromus. The mean lifespan was nearly equal for Bromus and Brachypodium, the leaf blades of Arrhenatherum reached a shorter lifespan. At the beginning Arrhenatherum was the dominant species in all four mixtures. But the composition of the mixtures altered during the exposition period. Arrhenatherum lost his dominant position in the vicinity of Bromus independent of the NHy-supply, without NHy-enrichment and under the supply with only one NHy-form Bromus became the dominant species. Brachypodium also increased his portion of the shoot biomass at the expense of Arrhenatherum, Brachypodium became dominant without NHy-supply and under high NH3-concentrations, but under NH4+-enrichment Arrhenatherum was able to persist. The relations in the competition between Bromus and Brachypodium were marked by clear oscillations, in the exposition period none of the two species became dominant. Under the growth conditions in this study Bromus and Brachypodium were more competitive than Arrhenatherum. The most important reason therefore can bee seen in the decrease of the root/shoot-ratio of Arrhenatherum under a combined NH3- and NH4+-supply. In combination with nutrient losses due to the harvests and the high nutrient demand which is among other things due to the short lifetime of the plant organs it is very likely that this leads to growing deficiency of other nutrients apart from nitrogen over time. Arrhenatherum was not able to spread out, not even under an elevated NH3/NH4+-supply. This lead to the conclusion that there is only a small possibility that species with higher nitrogen demands will spread in regularly used chalk grasslands. Under nitrogen deficiency Brachypodium was weaker than Bromus, but its shadow tolerance enabled Brachypodium to use an elevated NH3/NH4+-supply for a massive growth promotion. The very dense stands of Brachypodium in the field lead to the displacement of short species with negative consequences for the species diversity in chalk grasslands.

Stimulation of nitrification and denitrification by long term (from years to decades) grazing has commonly been reported in different grassland ecosystems. However, grazing generally induces important changes in plant species composition, and whether changes in nitrification and denitrification are primarily due to changes in vegetation composition has never been tested. We compared soil nitrification- and denitrification-enzyme activities (NEA and DEA, respectively) between semi-natural grassland sites experiencing intensive (IG) and light (LG) grazing/mowing regimes for 13 years. Mean NEA and DEA (i.e. observed from random soil sampling) were higher in IG than LG sites. The NEA/DEA ratio was higher in IG than LG sites, indicating a higher stimulation of nitrification. Marked changes in plant species composition were observed in response to the grazing/mowing regime. In particular, the specific phytomass volume of Elymus repens was lower in IG than LG sites, whereas the specific volume of Lolium perenne was higher in IG than LG sites. In contrast, the specific volume of Holcus lanatus, Poa trivialis and Arrhenatherum elatius were not significantly different between treatments. Soils sampled beneath grass tussocks of the last three species exhibited higher DEA, NEA and NEA/DEA ratio in IG than LG sites. For a given grazing regime, plant species did not affect significantly soil DEA, NEA and NEA/DEA ratio. The modification of plant species composition is thus not the primary factor driving changes in nitrification and denitrification in semi-natural grassland ecosystems experiencing long term intensive grazing. Factors such as trampling, N returned in animal excreta, and/or modification of N uptake and C exudation by frequently defoliated plants could be responsible for the enhanced microbial activities.

This work was undertaken to measure the in situ phytoextraction of zinc using a former zinc-smelter site where metallophyte plants have been growing for 30 years. The site exhibited a gradient in the total metal concentration in the upper horizon (from 3230 to 8530 mg Zn kg −1 ). Soils were sampled from four different sectors (I–IV), and plant shoots were harvested, identified, their biomass weighed and analysed for zinc. The results showed that three plant species were dominant on the site, including Arabidopsis halleri (cress), Armeria maritima (seathrift), and Arrhenatherum elatius (fromental). A. maritima was the predominant species according to the biomass production on the most polluted sector I. As the concentration of metals in soils decreased, A. maritima disappeared and A. halleri increased. The biomass of A. elatius was the highest on the less polluted soils. Concentrations in zinc in the aerial parts of plants varied from 73 (sector IV) to 6269 mg kg −1 DM (sector I). The concentration of Zn in A. halleri decreased with the decrease in concentration of zinc in soil. Phytoextraction was calculated from the biomass and its concentration of metal. It was at a maximum in sector III with a high contribution of A. halleri and A. elatius and reached 10 kg Zn ha −1 , a promising amount for phytoextraction considering the absence of any agricultural practices. In sector I, phytoextraction was four times lower despite a 2.6 times higher concentration of Zn in the upper horizon. In conclusion, phytoextraction was strongly dependent on the concentration of the available metal in soils which may limit the growth of plants, and favour tolerant but low biomass plant species such as A. maritima .

International audience; Population differentiation in variable environments is often related to the different local selection pressures that plants may experience. We examine the relation between reproductive success and morphological and phenological traits in woodland and open habitat populations of the tetraploid grass Arrhenatherum elatius. The reproductive correlates of morphological and phenological variation were estimated in woodland and open habitats, and on plants from each of three populations from woodland and three from open habitats grown in a garden environment at two light intensity levels. Genetic variation in these populations was estimated in uniform conditions. # Temporal and spatial differences in phenotypic selection on morphology and phenology were observed within and between the two sites. Plants from the two sites showed significant phenotypic and genetic differences, and there is a dramatic reduction in reproductive success in the woodland habitat and in plants from this habitat grown in the two garden environments. # In controlled conditions, selection patterns were similar to those observed in natural habitats, suggesting that light availability may be an important ecological factor involved in population differentiation in A. elatius. The presence of significant genetic variability for the studied traits indicates the presence of a genetic potential to respond to the detected selection pressures. # We argue that a clear understanding of patterns of local adaptation and phenotypic selection in this species requires that they are examined in the light of regional processes related to seed dispersal and relative abundance in open and woodland habitats.

International audience; 1 Phenotypic plasticity and genetic differentiation may influence how natural populations colonize variable environments, and thus help explain differences in distribution of closely related taxa. The response to shading in woodland and open habitat populations of endemic diploid and widespread tetraploid Arrhenatherum elatius was studied. 2 Two questions were examined. (i) Does the widespread tetraploid A. elatius ssp. elatius show greater phenotypic homeostasis in fitness-related traits than the related Mediterranean endemic diploid ssp. sardoum? (ii) Do the two ploidy levels differ in patterns of population differentiation related to the original habitat? 3 For each ploidy level, 10 genotypes from each of three populations from woodland and three from open habitats were grown in a garden environment at two light intensity levels. 4 No differences in phenotypic plasticity of morphological, phenological and fitness-related traits studied were observed between the ploidy levels. Tetraploids showed greater vegetative and inflorescence size. 5 Tetraploid populations showed evidence of differentiation in relation to original habitat conditions: plants from open habitats had higher seed production, were taller and flowered earlier than populations from woodland habitats in both garden environments, but phenotypic plasticity did not differ between the two habitat types. No variation in phenotypic plasticity or population differentiation was observed among diploid populations from either habitat. 6 The lack of differences in plasticity between diploids and tetraploids, and the greater differentiation between woodland and open populations in tetraploids, are discussed in relation to the geographical distribution of the two ploidy leve

International audience; Plant populations with different ploidy levels have frequently been found to develop mechanisms of reproductive isolation when they occur in contact, presumably because of selection against the production of inviable or sterile hybrids. A parapatric contact zone between diploid and tetraploid Arrhenatherum elatius has been identified in the Spanish Pyrenees. Of 145 flowering plants sampled in the zone one was triploid. This study provides data on enzymatic allele frequencies, flowering time and selfing rate across the contact zone, to examine whether reproductive isolation occurs to limit the potential production of triploids. To substantiate these data, flowering time was measured in plants grown in a common garden and outcrossing rates were compared to those in one allopatric population of each cytotype from an environmentally similar habitat. Nei's genetic distances calculated on the basis of allele frequencies showed no clear evidence for past hybridization and/or introgression between diploids and tetraploids. Patterns of flowering phenology in the field and in controlled conditions indicated almost total flowering divergence between parapatric cytotypes; this divergence may be under genetic control. There was, however, no evidence of current phenotypic selection on flowering date in the contact zone. For each cytotype, multilocus selfing rates were higher in parapatric populations than in allopatric populations. The possibility that flowering time divergence and increased selfing have evolved in the contact zone resulting in reproductive isolation is discussed.

Phenotypic plasticity may play a critical role in the response of natural populations to selective pressures in variable environments and may help explain differences in the ecological and geographical distribution of closely related taxa. In this study we quantify phenotypic plasticity in three subspecies of the European grass polyploid complex Arrhenatherum elatius, ssp. sardoum, elatius, and bulbosum, to test two hypotheses: (i) Does the widespread tetraploid ssp. elatius show greater phenotypic homeostasis in fitness related traits than its Mediterranean endemic related diploid ssp. Sardoum? (ii) Does the corm-forming tetraploid ssp. bulbosum (which is widespread throughout northwest Europe) differ from ssp. elatius (which does not have corms) in patterns of resource allocation across environments? Eight genotypes from each of two populations of each subspecies were cloned and grown in four replicated garden environments (a combination of two light and nutrient levels). Mean reaction norms for each subspecies showed no consistent variation between tetraploids and diploids in the plasticity of fitness-related traits over the range of the studied environments. Tetraploid genotypes showed consistently greater values than diploids across all environments, which may partly explain the more widespread distribution of tetraploids. The two tetraploids differed in patterns of resource allocation across environments, with ssp. bulbosum maintaining a relatively more constant vegetative to floral biomass ratio across three of the four environments. Keywords: phenotypic plasticity, ploidy levels, corm production, Arrhenatherum elatius.

Nitrogen losses from plants may occur through a variety of pathways, but so far, most studies have only quantified losses ofnutrient by above-ground litter production. We used 15N pulse labelling to quantify total nitrogen losses from above-and belowground plant parts. Using this method we were able to inelude also pathways other than above-ground litter production. To test the hypothesis that species from nutrientpoor habitats lose less nitrogen than species from more fertile soils six perennial grasses from habitats with a wide range ofnutrient availability were investigated: Lolium perenne, Arrhenatherum elatius, Anthoxanthum odoratum, Festuca rubra" Festuca ovina and Molinia caerulea. The results ofan experiment carried out in pots in a greenhouse at two fertility treatments show that statistically significant losses occur through pathways other than litter production. In the low fertility treatment, most (70010) losses from L. perenne occurred by litter production, but in A. elatius, F. rubra, F. ovina and M. caerulea. more than 50% oflabelled N losses took place by root tumover, leaching or exudation from roots. When nutrient supply increased, the 15N losses in above-ground dead material increased in all species and in A. elatius, A. odoratum and F. rubra the 15N losses vía other pathways decreased. Ranked according to decreasing tumover coefficient the sequence of species was: L. perenne, A. odoratum F. rubra. F. ovina" A. elatius, M. caerulea These results show that species adapted to sites with low availability ofnutrients lose less nitrogen (incIuding above-and belowground losses) than species adapted to more fertile soils., This work was supported by a grant from the Spanish Ministry ofEducation and Science. Thanks are due to JG Heij for technical assistance, to GW Va1kenburg for analysing the labelled samples and to JCM Withagen for statistical help.

1. To find out which properties enable plant species to dominate in nutrient-poor habitats and which properties benefit species in nutrient-rich habitats, we studied the growth and morphology of eight perennial grass species from habitats with contrasting soil fertilities in a pot experiment under controlled conditions in a glasshouse. 2. The species were grown under nutrient-poor and nutrient-rich conditions. Ranked from the least responsive to the most responsive to the supply of nutrients they were: Festuca ovina, F. rubra, Anthoxanthum odoratum, F. arundinacea, Alopecurus pratensis, F. pratensis, Arrhenatherum elatius, Lolium perenne. 3. The response correlated positively with the Ellenberg nitrogen number of the species. No differences in initial relative growth rate were found between the species, but after 4 weeks the plant dry weight increased with increasing nitrogen number as a result of variation in embryo plus endosperm weight. 4. Species characteristic of nutrient-rich hayfields are taller and show a more homogeneous vertical distribution of photosynthetic area than the species from nutrient-poor habitats, which have most of their leaf area below 15 cm. Species from the nutrient-poor habitats allocated less dry matter to the roots and consequently more to the shoot, than species from nutrient-rich conditions. However, leaf and root morphology seem to be most clearly adapted to the habitat. 5. Species from nutrient-rich habitats have a higher specific leaf area (SLA) than species from nutrient-poor habitats, while species from nutrient-poor habitats had more root length per unit root weight (SRL) than species from nutrient-rich habitats.

This experiment was carried out to evaluate the potential of seven genotypes of perennial grasses of winter for use in animal systems: Bromus auleticus, Dactylis glomerata, Phalaris aquatica, Festuca arundinacea cv Epagri 312 (0 and 40% of Endophytic fungi), Festuca arundinacea cv ‘au Triumph’ and Arrhenatherum elatius, in the climatic conditions of North Plateau of Santa Catarina State, Brazil, during two consecutive years of 2006 and 2007. Treatments were arranged in a randomized complete block design with four replicates. Were evaluated forage mass of genotypes and ground cover (%). In the year of 2006 the crude protein (CP) and digestibility in vitro of organic matter (DIVOM) were evaluated in the spring. All the genotypes presented contents of CP above of 20 dag kg -1 and DIVOM above of 65 dag kg -1 . There was significant interaction (p < 0,05) between genotypes and season for forage mass. In 2006 the forage mass of the genotypes was greater in the spring. In 2007, with exception of the Bromus and Arrhenatherum no have difference in the forage mass among spring and winter. There was significant interaction (p < 0,05) between genotypes and ground cover (%). In the second year all the genotypes reduced the ground cover (%). On the average of two years, the yield potential of DM ranged from 3,3 to 5,2 t ha -1 respectively for Bromus and Arrhenatherum. The results would suggest that the genotype Phalaris aquatica have annual cycle and the genotypes Arrhenatherum elatius, Festuca arundinacea cv Epagri 312 (0% Endophytic fungi) and Festuca arundinacea cv au Triumph present potential of use for the region.

International audience; Three pairs of adjacent populations of Arrhenatherum elatius were studied both for their genetic diversity and for their genotypic structure. Each pair consisted of one population on a normal soil type and the other on spoil from mining. Using morphological characters as well as allozyme markers, the genetic diversity in populations on toxic soils (mining spoil) was found to be higher than in populations in normal pasture. This suggests that the tolerant populations have been built up from a large number of tolerant genotypes emanating from normal pasture populations in which tolerance genes are not uncommon. The higher genetic diversity of the tolerant population has then been maintained by the spatial heterogeneity of toxic habitats, or less intense selective forces of biotic origin (e.g. intraspecific competition) or by a more open breeding system. Variations in allozymes gave interesting clues. No clear cut differences in the genetic structure between pairs of populations were found, but there was a higher heterozygote deficit in denser populations. This might arise from inbreeding because of a more limited gene flow in dense populations. The higher genetic diversity of sparse populations on toxic soil might partly result from the effectively greater gene flow into these populations in which individuals must trap pollen from longer distances than do individuals in dense populations.

Philippe Vandenkoornhuyse et al. (“Extensive fungal diversity in plant roots,” Brevia, 15 March, p. [2051][1]) report on various new and unusual fungi from roots of the grass plant Arrhenatherum elatius . I won't quibble about the putative identification and taxonomic grouping of the fungi involved, but the authors strongly suggest a necessary relationship between the fungi recovered and the plants themselves. I contend that it is just as likely that these fungi were associated with the plants simply by accident. Root sampling and cleaning techniques were not well described, but plant roots commonly have wounds associated with them even before sampling. Many organisms may become passively associated with such wounds or may even be drawn up into the nonliving root xylem if this is exposed to soil and soil water. Polymerase chain reaction techniques are so powerful that even traces of accidental associations would be detected. Thus, I contend that many of the novel organisms detected by the authors could simply be passive associations of soil organisms that have no necessary involvement directly with the roots of these plants. On the basis of DNA extractions from soil directly, we are all aware that most soil microorganisms have yet to be identified because they fail to culture easily on common growth media. The ones described by Vandenkoornhuyse et al. could simply be from that great array. # Response {#article-title-2} In our Brevia, we characterize fungal diversity in a mundane ecological niche, the roots of a plant. Sequences from roots of Arrhenatherum elatius revealed an unexpected diversity, with all known fungal phyla represented. The diversity within these phyla is very high, with a large proportion of fungi that could not be related to any known SSU rRNA gene sequence. The cleaning procedure of the root surface was designed to remove the mineral and organic particles. With this strategy, it is impossible to clean the inner root structures such as xylem. However, observations of stained roots under microscope showed only arbuscular mycorrhiza (Glomales) and septate endophytic fungal structures within or between the root cortical cells and a network of septate fungal filaments on the root surface. These external hyphae did not form the typical structures of ectomycorrhiza, nor did we observe any symptoms of plant pathology. Crowe addresses, in part, the question of the ecological functions of these fungi associated with roots. One fungal group that we certainly did expect to find represented in roots was the arbuscular mycorrhizal (AM) fungi ([1][2], [2][3]). These ubiquitous biotrophic zygomycetes in the order Glomales form symbioses with more than 80% of land plants ([3][4]). The co-occurrence of different symbiotic AM fungal phylotypes within the roots of a plant species is in agreement with previous work ([1][2], [2][3]). However, our results show clearly that the Glomales correspond only to a small fraction of the fungal diversity in these roots. We can only speculate on the possible roles of the other 94% of the root fungal diversity found here. Further studies are required to know which part of root fungal diversity interacts actively with host plant. A better knowledge of the diversity of the fungal world and a better understanding of fungal ecological functions in ecological niches and ecosystems are likely to become important issues. 1. [↵][5]1. T. Helgason, 2. T. J. Daniell, 3. R. Husband, 4. A. H. Fitter, 5. J. P. W. Young , Nature 394, 431 (1998). [OpenUrl][6][CrossRef][7][PubMed][8] 2. [↵][9]1. T. Helgason, 2. A. H. Fitter, 3. J. P. W. Young , Mol. Ecol. 8, 659 (1999). [OpenUrl][10][CrossRef][11][Web of Science][12] 3. [↵][13]1. S. E. Smith, 2. D. J. Read , Mycorrhizal Symbiosis (Academic Press, San Diego, CA, ed. 2, 1997). [1]: /lookup/doi/10.1126/science.295.5562.2051 [2]: #ref-1 [3]: #ref-2 [4]: #ref-3 [5]: #xref-ref-1-1 "View reference 1 in text" [6]: {openurl}?query=rft.jtitle%253DNature%253B%2BPhysical%2BScience%2B%2528London%2529%26rft.stitle%253DNature%253B%2BPhysical%2BScience%2B%2528London%2529%26rft.aulast%253DHelgason%26rft.auinit1%253DT.%26rft.volume%253D394%26rft.issue%253D6692%26rft.spage%253D431%26rft.epage%253D431%26rft.atitle%253DPloughing%2Bup%2Bthe%2Bwood-wide%2Bweb%253F%26rft_id%253Dinfo%253Adoi%252F10.1038%252F28764%26rft_id%253Dinfo%253Apmid%252F9697763%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [7]: /lookup/external-ref?access_num=10.1038/28764&link_type=DOI [8]: /lookup/external-ref?access_num=9697763&link_type=MED&atom=%2Fsci%2F296%2F5575%2F1969.1.atom [9]: #xref-ref-2-1 "View reference 2 in text" [10]: {openurl}?query=rft.jtitle%253DMol.%2BEcol.%26rft.volume%253D8%26rft.spage%253D659%26rft_id%253Dinfo%253Adoi%252F10.1046%252Fj.1365-294x.1999.00604.x%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Ajournal%26ctx_ver%253DZ39.88-2004%26url_ver%253DZ39.88-2004%26url_ctx_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%253Actx [11]: /lookup/external-ref?access_num=10.1046/j.1365-294x.1999.00604.x&link_type=DOI [12]: /lookup/external-ref?access_num=000080177700013&link_type=ISI [13]: #xref-ref-3-1 "View reference 3 in text"

We tested the hypothesis that species characteristic of nutrient rich sites always grow faster than species from nutrient poor sites, but have a shorter organ life span. It has been suggested that this fast tissue turnover may limit their performance at nutrient poor sites. Three ecologically contrasting grasses were studied: Bromus erectus, characteristic of nutrient poor meadows, and Arrhenatherum elatius and Dactylis glomerata, characteristic of more nutrient rich grasslands. These species were grown at three meadows differing in nutrient availability and harvested 3, 7, 9.5 and 11 months after germination. D. glomerata produced at all sites the largest total biomass. B. erectus showed the lowest growth response to site conditions. D. glomerata and A. elatius had a faster leaf turnover than B. erectus. D. glomerata had a faster root turnover than B. erectus. Root turnover of A. elatius was probably also faster than that of B. erectus, but this was partially obscured by decomposition of dead roots. D. glomerata and A. elatius had a lower tissue density of leaves and roots than B. erectus. We conclude that there is a negative correlation between the plant's ability to increase its growth with increasing nutrient availability and the tissue life span. Nutrient losses due to fast tissue turnover may prevent the dominance of fast-growing species at nutrient poor sites, although these species are in general better at nutrient acquisition. The negative correlation between growth rate and tissue longevity is to a large extent a result of constraints caused by plant tissue structure.

CO 2 -enrichment experiments have been performed on 15 British herbaceous species of widely differing ecology. The conditions of growth were very similar to those used in a previous study and involved full-light glasshouse conditions, non-limiting supplies of water and mineral nutrients and a daytime mean temperature of 18 °C. Four CO 2 treatments were maintained (350, 500, 650 or 800 vpm) over periods of 49 or 52 days. Hyperbolic functions were fitted to yield vs CO 2 concentration. The functions were used to generate predictions of Q 540/350 (the quotient of the «present» yield which is predicted for the CO 2 regime expected by the year 2050) and Q 700/350 (the quotient predicted for a doubling of the present ambient CO 2 concentration). Values of Q 540/350 for whole-plant dry weight ranged from below 1.00 to 1.19 (...)

1. The generation of shoot thrust was measured in eight contrasted herbaceous species (Arrhenatherum elatius, Bromus erectus, Campanula rotundifolia, Cerastium fontanum, Hypericum perforatum, Koeleria macrantha, Poa trivialis and Urtica dioica) using a framework of weighted windows that could be opened by an expanding shoot. 2. The species that occur as vegetation dominants in their usual habitats (A. elatius, B. erectus and U. dioica) were found to have the greatest ability to generate thrust

The effects of increase in copper contamination in potting compost/copper mine waste mixtures on the germination and growth of the following species has been examined: Agrostis tenuis, Poa trivialis, Lolium perenne, Dactylis glomerata, Cynosurus cristatus, Anthoxanthum odoratum, Arrhenatherum elatius, Plantago lanceolata and Trifolium repens. Copper tolerant A. tenuis from Parys Mountain was used as control. Plant dry weight and plant height decreased with increase in proportion of copper contaminated soil in the mixtures, a conspicuous characteristic was the continued survival and growth of some individuals and the death of others at 1-4, 1-8 and mine soil levels. Agrostis tenuis and Dactylis glomerata produced fully copper tolerant survivors at a frequency of 0·08 per cent. By contrast Poa trivialis, Lolium perenne, Arrhenatherum elatius and Cynosurus cristatus produced survivors having indices of tolerance ranging from 7 to 20 per cent, tolerance, values too low to be considered as fully copper tolerant. Plantago lanceolata, Anthoxanthum odoratum, and Trifolium repens, failed to produce any survivors at all. The heritability of copper tolerance in the selected material: Agrostis tenuis, Lolium perenne, Dactylis glomerata, Arrhenatherum elatius, and copper tolerant A. tenuis was determined. Heritability is discussed in terms of breeding value. The results suggested that while the evolution of tolerance would be easy in A. tenuis it would be difficult in species such as Lolium perenne. The data presented are interpreted as evidence that the exclusion of some species from mine areas is because of their inability to evolve metal tolerance.

Freshly collected ripe caryopses of twenty-five indigenous grasses were mixed with the top 7–5 cm of sterilized soil confined in cylinders sunk in the ground and cultivated three times yearly. There was a flush of seedlings of most species shortly after sowing, but species differed in the persistence of viable seeds. About one third, including Bromus sterilis, B. hordeaceus, Lolium perenne ssp. perenne, Arrhenatherum elatius and Alopecurus pratensis, produced few seedlings after the initial flush. Others such as Deschampsia cespitosa, Holcus lanatus and Poa trivialis, recognized as forming persistent seed banks in grassland soils, produced appreciable numbers of seedlings in the second year after sowing. Most persistent were species that occur as arable weeds (Avena fatua, Poa annua) or in wetlands (Glyceria plicata, G. maxima, Alopecurus geniculatus). Emergence from the seed bank generally followed soil disturbance but some species (Aira praecox, Avena fatua, A. sterilis ssp. ludoviciana, Danthonia decumbens) exhibited consistent seasonal patterns which may be associated with cyclic changes in germination requirements of the buried seeds.

The growth rate and feeding behaviour of Wiseana cervinata larvae supplied with the foliage of a range of legumes and grasses were studied. Mortality of larvae supplied with Lotus pedunculatus and Arrhenatherum elatius was 94–100% within 30 davs. Weight gains of larvae feeding on Lotus corniculatus, L. pedunculatus × corniculatus, L. tenuis, Anthoxanthum odoratum, Dactylis glomerata, Holcus lanatus, and Phalaris tuberosa were less than those of larvae fed on Trifolium repens and Lolium hybrid cv. ‘Grasslands Manawa’.

Summary: Populations of Arrhenatherum elatius var bulbosum were established either from seed or vegetatively and studied under four cultivation regimes. Treatments were carried out in the autumn and winter and the experiment was sown with barley in the following spring. Winter mouldboard ploughing gave the greatest reduction of tillers and bulbs of established plants, but was less effective when preceded by rotary cultivation in the early autumn. Tine cultivations increased the numbers of tillers and bulbs, but the largest increase in growth was recorded on plots that were not cultivated. The germination of seeds was not affected by early autumn cultivations. Mouldboard ploughing, tine cultivation and paraquat at 060 kg a. i. /ha each gave complete control of seedlings in winter. A simple test on the morphology of plants grown from seed agreed with earlier conclusions that the bulbous form is not a distinct variety. It is suggested, nonetheless, that the bulbous form should be named seperately as in practice it alone succeeds as an arable weed. Resume: Croissance d'Arrhenatherum elatius var bulbosum (Willd.) Spenn. dans de l'orge de printemps, sous l'influence des facons culturales Des populations d'Arrhenatherum elatius var bulbosum ont ete implantees soit a partir de semences, soit vegetativement; ellesont eteetudiees sous quatre regimes de culture. Les traitements ont ete effectues en automne et en hiver et le materiel experimente a ete seme avec l'orge au printemps suivant. Le labour d'hiver avec versoir a donne la plus grande reduction des pousses et des bulbilles des plantes etablies, mais il a ete moins efficace lorsqu'il a ete precede d'une facon au rotavator, au debut de l'automne. Les scarifications ont accru le nombre de pousses et de bulbilles mais l'accroissement le plus important de la croissance a ete constate dans les parcelles non travaillees. La germination des semences ňa pas ete influencee par des facons culturales effectuees tot en automne. Le labour, la scarification et le traitement au paraquat a 0.600 kg/ha (m.a.) ont detruit totalement les plantules en hiver. Un test simple sur la morphologie des plantes issues de semences Concorde avec les premieres conclusions, a savoir que la forme a bulbilles ňest pas une variete distincte. II est neanmoins suggere que la forme a bulbilles pourrait etredesignee par un nom different car, en principe, elle est seule a reussir comme mauvaise herbe des terres cultivees. Zusammenfassung Entwicklung von Arrhenatherum elatius var. bulbosum (Willd.) Spenn. in Sommergerste in Abhangigkeit von verschiedenartiger Bodenbearbeitung Populationen von Arrhenatherum etatius var, butbosum wurden sowohl aus Samen als auch vegetativ angezogen und bei vier Bodenbearbeitunsgverfahren beobachtet. Die MaBnahmen wurden im Herbst und Winter durchgefuhrt und der Versuch im folgenden Fruhjahr mit Gerste bestellt. Bei bereits etablierten Pflanzen ergab Pflugen im Winter die groste Beeintrachtigung der spateren Bestockung und Knollenbildung, war jedoch weniger wirksam. wenn eine Frasbearbeitung im fruhen Herbst vorausging. Grubbern erhohte die Zahl der Bestockungsknoten und Knollen. Die groste Wachstumszunahme wurde jedoch auf unbearbeiteten Parzellen erzielt. Die Keimung der Samen wurde durch Bearbeitung im fruhen Herbst nicht beeinflust, Pflugen, Grubbern und Behandlung mit 0.6 kg/ha A.S. Paraquat ergab jeweils vollstandige Vernichtung der Samlinge im Winter. Ein einfacher Vergleich der Pflanzenmorphologie bei aus Samen gezogenen Pflanzen stimmte mit fruheren Feststellungen uberein, daβ die Knollenform keine deutlich abgegrenzte Varietat darstellt. Dennoch wird vorgeschlagen, die Knollenform als eigene systematische Einheit abzugrenzen, da nur sie sich als Ackerunkraut erfolgreich durchsetzt.

Mefluidide was applied at 150ga.i.ha−1 on one of three dates (7, 28 March or 18 April, 1984) to irrigated field plots of nine grasses. Spraying suppressed flowering in the primary growth of most species, especially when carried out in mid- April. However, spraying at this time proved too damaging to amounts of herbage harvested. Spraying in March reduced mean yields by about one-third at the first harvest and increased mean yields at the second harvest. In addition, spraying at this time increased herbage quality, as indicated by higher N and lower fibre contents, at least at the first harvest. In general, the grasses most responsive to mefluidide were tall-growing and/or early-flowering species, e.g. Arrhenatherum elatius, Festuca rubra, Dactylis glomerata and Holcus lanatus; by comparison, Lolium perenne was relatively less affected by spraying. The findings indicate the potential of mefluidide for overcoming the normal decline in herbage quality associated with flowering, and for transferring growth from spring to midsummer, albeit at some cost to total annual production.

SUMMARY The oviposition preferences of Oscinella frit, O. vastator, O. nitidissima, O. albiseta andO. nigerrima for differenct Gramineae were investigated in the laboratory. O. frit, laid most eggs on oats, Lolium multiflorum and Festuca rubra, relatively few eggs were laid on barley and virtually none on Dactylis glomerata None of the other Osinella species oviposted on cereals. Of the other species, O. vastator appeared to be the most polyphagous and the preferred hosts were L. multiflorum, Lolium perenne and Festuca pratensis; few eggs were laid on either F. rubra, Agrostis tenuis or Poa pratensis. The host ranges of the remaining species were much more limited. Although a few eggs were laid by O. nitidissima on Lolium, the preferred host was A. tenuis. Oscinella albiseta oviposited only on D. glomerata whilst nearly all the eggs laid by O. nigerrima were deposited on shoots of Arrhenatherum elatius. The distribution of eggs by O. frit on L. multiflorum and A. tenuis was different from that on oats; on grasses most eggs were laid inside withered leaf sheaths whereas on oats most were deposited inside the coleoptile. The oviposition sites of O. nitidissima, O. nigerrima and O. albiseta on their respective host grasses were similar to those of O. frit on grasses. O. frit laid most eggs on grasses which were at the five-leaf stage and tailoring.

The paper summarizes the results of a series of experiments on enumeration of N2-fixing bacteria (diazotrophs) and hormonal effects of Azospirillum on root development. Numbers of N2-fixing and N-heterotrophic bacteria were determined on the root (rhizoplane plus “inner” root surface) and in the rhizosphere soil (0–3 mm from the root surface) of Arrhenatherum elatius, other forage grasses and some herbaceous plant species. Pot experiments involved freshly collected soil from an unfertilized grassland area containing its natural population of N2-fixing bacteria. The MPN (most probable number) of diazotrophs in relation to the MPN of the total bacterial population was always lower on the root than in the rhizosphere soil, suggesting that diazotrophs were not selectively advantaged at the root surface. Supply of mineral nitrogen (NH4NO3) decreased the proportion of N2-fixing bacteria at the rhizoplane as well as in the rhizosphere soil. Similar results were obtained when N was supplied via the leaves. The data suggest that N2-fixing bacteria in the rhizosphere are poor competitors once they loose their competitive advantage of binding dinitrogen. Correspondingly, the increase in the MPN of the diazotrophs found during plant development was interpreted as a result of decreased available combined N in the rhizosphere. The proportion of N2-fixing bacteria relative to the total number of bacteria was generally below 1%. Considering the potential amount of substrate released from the roots and the substrate requirement of the bacterial population, N2-fixation was considered insignificant for plant growth under the given conditions. For the investigations on possible beneficial effects on plant development by bacterial hormones, Azospirillum brasilense was chosen because evidence suggests that amongst the soil bacteria releasing hormones, especially IAA, certain strains of this species are more important than other bacteria. Application of A. brasilense Cd (ATCC 29710) onto the roots of young wheat plants grown in soil increased the number of lateral roots, the total root length and the number of root hairs. Similar results were obtained after application of IAA. This suggests that IAA is an important factor responsible for the effects observed after inoculation with A. brasilense. The increase in root surface may improve acquisition of nutrients and enhance growth of plants. Another hormonal effect of A. brasilense was an increase in nodulation of Medicago sativa grown on agar. Again pure IAA resulted in a similar increase in nodule number. Increases in nodule number were only in part associated with a change in root morphology. Therefore an effect of IAA on the plant immanent regulation system for nodulation is likely. N2-fixierende Bakterien in der Rhizosphare: Quantifizierung und hormonelle Wirkung auf die Wurzelentwicklung In der vorliegenden Arbeit wird eine Ubersicht uber langfristige Unter-suchungen zur zahlenmasigen Erfassung N2-fixierender Bakterien in der Rhizosphare und zu Wirkungen bakterieller Hormone auf die Wurzelentwicklung gegeben. Mit Hilfe der “most probable number” - Methode (MPN) wurde die Zahl N2-fixierender und N-heterotropher Bakterien an der Wurzel (Rhizoplane plus “innere” Wurzeloberflache) und im Rhizospharenboden (Boden bis 3 mm Entfernung von der Wurzel) von Arrhenatherum elatius, anderen Futtergrasern sowie einigen krautigen Pflanzenarten bestimmt. Fur die Gefasversuche wurde ein Boden von einem ungedungten Standort mit Gras- und Krautervegetation und der naturlichen Population N2-fixierender Bakterien verwendet. Eine selektive Anreicherung von N2-fixierenden Bakterien an der Wurzel konnte nicht festgestellt werden; bei allen Versuchen war der Anteil der diazotrophen Bakterien an der gesamten Bakterienpopulation an der Wurzel niedriger als im Rhizospharenboden. Die Zugabe von mineralischem Stickstoff zum Boden erniedrigte den Anteil N2-fixierender Bakterien an der Gesamtpopulation sowohl an der Wurzel als auch im Rhizospharenboden. Das Ergebnis war ahnlich, wenn die Pflanzen mit Stickstoff uber die Blatter versorgt wurden. Diese Ergebnisse zeigen, das N2-fixierende Bakterien wenig konkurrenzkraftig sind, wenn sie den Vorteil der Fixierung von atmospharischem Stickstoff verlieren. In entsprechender Weise wird die gefundene Zunahme der diazotrophen Bakterien mit zunehmendem Pflanzenalter interpretiert, da es durch den Entzug durch die Pflanze zur allmahlichen Verarmung an Stickstoff im Boden kommt. Der Anteil der N2-fixierenden Bakterien an der Gesamtzahl der Bakterien lag unter 1%. In Anbetracht der begrenzten Mengen an energiereichen Verbindungen, die von der Wurzel freigesetzt werden, wird daher der Beitrag der N2-Fixierung in der Rhizosphare fur das Pflanzenwachstum unter den gegebenen Bodenbedingungen und bei den untersuchten Pflanzenarten als unbedeutend angesehen. Fur die Untersuchungen zum moglichen Einflus von bakteriellen Hormonen auf die Wurzelentwicklung wurde Azospirillum brasilense gewahlt, da es Hinweise darauf gibt, das diese Art mehr Hormone, insbesondere IES, abgibt als andere Bodenbakterien. Applikation von A. brasilense Cd (ATCC 29710) direkt an die Wurzeln junger Weizenpflanzen (Kultivierung im Boden mit Wurzelwachstum entlang einer abnehmbaren Glasplatte) ergab eine Forderung der Gesamtlange der Wurzel sowie der Zahl der Seitenwurzeln und Wurzelhaare. Ahnliche Ergebnisse wurden durch die Applikation von IES erzielt. Es ist daher anzunehmen, das vor allem IES fur die aufgetretenen morphogenetischen Veranderungen verantwortlich ist. Die gefundene Vergroserung der Wurzeloberflache kann vor allem uber die Verbesserung der Nahrstoffaufnahme zu einer Wachstumsstimulation der Pflanze fuhren. Bei Medicago sativa (Kultivierung auf Agar) erhohte eine Inokulation mit A. brasilense die Knollchenzahl. Auch in diesem Fall wirkte IES-Applikation ahnlich. Es wird angenommen, das die Forderung der Nodulation weniger mit morphogenetischen Veranderungen der Wurzel im Zusammenhang steht als mit dem Einflus von IES auf das Autoregulationssystem der Pflanze fur die Knollchenzahl.

In a solution-culture experiment in a controlled environment, seedlings of four native grasses of contrasted ecology were compared with respect to their response to manganese concentrations over the range 5–200 mg/l. The order of susceptibility to manganese toxicity (Arrhenatherum elatius > Agrostis tenuis > Festuca ovina > Deschampsia flexuosa) is inversely correlated with the ability of these species to colonise acidic soils. re]19760213

Phialophora graminicola and Phialophora sp. (lobed hyphopodia) are weakly or not pathogenic to the cereal and grass roots which they colonize and are also known to restrict the infection of these plants by Gaeumannomyces graminis. The occurrence of these fungi under 15 field-grown grass species has been studied using wheat as the test plant. P. graminicola occurred under all grass species tested but at different population levels. The lowest populations were found under Bromus erectus and B. inermis, and relatively low populations under Agrostis alba, Festuca ovina and Phalaris arundinacea. Festuca pratensis, F. rubra, F. arundinacea, Dactylis glomerata and Arrhenatherum elatius harboured the highest populations of P. graminicola. Phialophora sp. (lobed hyphopodia) was found at low population levels under 7 of the 15 grasses examined. The strains of P. graminicola isolated in these studies differed markedly in growth rate on wheat roots and in restriction of G. graminis on wheat grown in perlite (preliminary results).

In a 30-week field experiment, observations on growth and nutrient uptake in potted plants were made concurrently with soil and air temperatures on north- and south-facing slopes. Parallel observations were also made in a controlled environment. Growth in the field was slow but steady, declines in shoot weight fraction with time being matched by increases in rate of dry weight increment per unit of shoot. Increases in root weight fraction, however, failed to match low and declining rates of nitrogen uptake per unit of root; hence, nutrient concentrations generally declined with time. Thermal time in the form of degree-day integrals above the base 3°C was found to correlate well with growth, each degree day contributing a 0.16% increase in total dry weight, on average. Soil, locational and moisture effects caused this average to vary ca. two-fold in either direction.

The tolerance of seedlings of different seed populations of three grass species ( Festuca rubra L., Agrostis tenuis Sibth. and Arrhenatherum elatius J. and C. Presl—derived from a range of habitats) of the metals Cd, Zn, Cu, Pb and Ni was determined by means of relative root growth in metal-free and metal-enriched culture solutions. It was shown that all populations originating from metal-contaminated habitats possessed ‘multiple-metal-tolerance’, i.e. tolerance to more than one of the metals tested. Tolerance was most pronounced of those metals which were abundant in the original soils. A single population exhibited a remarkable Ni-tolerance, although this metal was not elevated in the population's natural habitat. The highest Cd-tolerance was found in populations which were also highly Zn/Pb-tolerant whereas Cu/Pb-tolerant populations did not show a significantly increased tolerance to Cd in solution culture. However, when growing plants on a range of CdO-enriched soils, either of the populations from metal-contaminated locations was less affected by the treatment than the respective non-tolerant control population. Measurements of yield, tissue Cd concentrations and activities of the enzymes acid phosphatase and peroxidase were performed. From the results it was postulated that Cd-tolerance could be related to the maintenance of lower Cd concentrations in shoots; the presence of an internal mechanism of Cd-tolerance in shoots seemed unlikely in the populations investigated.

The economic importance of Xanthomonas campestris pv. graminis on grasses has made it necessary to look for control measures. The most important is breeding for resistance. Different methods of selection were investigated and compared. Further, production of the inoculum, virulence, host specificity, disease assessment and yield losses of Arrhenatherum elatius were examined.

Various grass and herbaceous plant species (e.g. Arrhenatherum elatius L., Phleum pratense L., Planlago media L., Taraxacum officinale WEB.) were cultivated in a freshly collected soil from an unfertilized grassland area with its natural population of N2-fixing bacteria. Diazotrophs and total bacteria at the root surface (at outer plus “inner” surface as recovered in root homogenate) and bacteria in the rhizosphere soil (0–3 mm from root surface) were counted by the most probable number (MPN) method. Addition of mineral N (NH4NO3) to the soil decreased its nitrogenase activity (assayed by acetylene reduction) and also the proportion of diazotrophs among the heterotrophs. The result was similar when N was supplied via the leaves, probably owing to an increased release of N-containing compounds with lower C:N ratios from the root. The decrease in the proportion of diazotrophs suggests a competitive suppression by non-diazotrophs in the presence of combined N. Correspondingly, the increase in the MPN of N2-fixing bacteria found during plant development is interpreted as the result of a decrease in N in the soil, particularly in the rhizosphere, by uptake and in addition, a decrease in the N-concentration of the plant with a concomitant change in the C:N ratio of compounds released from the root. The proportion of diazotrophs among total bacteria varied greatly but was lower for bacteria living on or within the roots than for bacteria in the rhizosphere soil. Most of the N2-fixing bacteria were members of the genera Klebsiella and Enterobacter. Species of Azospirillum represented only a small proportion of the total counts.

Two experiments were conducted in which foliage-acting herbicides were applied to onion couch (Arrhenatherum elatius ssp. bulbosum). The first experiment used an artificially established population and investigated the effects of straw burning on the performance of autumn-applied treatments of glyphosate, aminotriazole and dalapon. Spring barley was sown without cultivation. The second experiment, conducted on a naturally occurring infestation, compared the performance of glyphosate applied at alternative autumn timings and a single application of flamprop-methyl made in the following spring, in the presence of a winter wheat crop. In the first experiment, assessments made after 15 months suggested that straw burning resulted in increased growth. In addition, herbicide performance appeared less effective after burning. In neither case were these differences significant. Glyphosate at 1·0 and 1·5 kg a.e./ha gave the highest levels of control of both shoots and bulbs, whereas control from aminotriazole at all doses (1·5, 3·0 and 4·5 kg a.i./ha) was poor. Dalapon (6·0, 12·0 and 18·0 kg a.i./ha) was intermediate in its effectiveness. In the second experiment, applications of glyphosate at 1·0 and 1·5 kg a.e./ha resulted in high levels of control of both shoots and bulbs with no significant difference between application dates. Flamprop-methyl at 0·52 kg a.i./ha reduced the number of shoots and bulbs by 55% and 58% respectively. All treatments significantly reduced the number of inflorescences present in July.

Arrhenatherum elatius (L.) Presl. (Oatgrass) and Bromus erectus Huds. (Bromegrass) were grown in pots in pure culture and with (a) root, (b) shoot and (c) root and shoot (total) competition with three levels of irrigation. There was one preliminary harvest of shoots and one final harvest of shoots and roots. Plant height, tiller number, and fresh and dry weight were recorded. The plant material was analyzed for protein and acid soluble nitrogen, for total ash, total lipids, carbon, DNA and RNA. The experiment took place in an unusually dry summer. For this reason both grasses showed nearly the same competitive ability. There was a slight advantage to Arrhenatherum under root and total competition, especially with watering, and a slight advantage for Bromus under shoot competition, with respect to competitive coefficients based on dry matter production. The most distinct effect was the reduction of the root system of Bromus under total competition with watering. The data clearly indicate that water is one of the factors for which Arrhenatherum and Bromus compete. Although there were only small changes in dry matter production, there were clear differences in the chemical composition of the plants. In the main part of the experiment, Arrhenatherum was able to increase its protein content under root and total competition, whereas Bromus showed a similar tendency only under shoot competition. These data confirm the earlier hypothesis that higher protein content of the green parts causes higher growth rate and thus indicates the stronger competitor. Both grasses exhibited an increase of carbon content under competition, whereas DNA and RNA, inversely related to each other, reacted specifically to root and shoot as well as total competition. These findings cannot be explained without further investigation.

In order to discuse the corology of some mediterranean grasses belonging to the tribe Aveneae, the original material from H. Knoche herbarium is studied. Three taxa, Avena sterilis L. var. maxima Pérez Lara, Arrhenatherum elatius subsp. baeticum Romero Zarco, and A. album (Vahl) W.D. Clayton var. album, are new records for the Balearic lslands.Se estudia el material original del herbario de H. Knoche para discutir la corología de algunas especies de gramíneas de la tribu Aveneae. Se citan tres nuevos táxones para las Islas Baleares: Avena sterilis L. var. maxima Pérez Lara, Arrhenatherum elatius subsp. baeticum Romero Zarco y A. Album (Vahl) W.D. Clayton var. album.

In laboratory experiments, roots of oats ( Avena sativa ) and the grass Arrhenatherum elatius caused attraction and subsequent lysis of zoospores of Allomyces arbuscula, Aphanomyces sp., Phytophthora cinnamomi, Pythium aphanidermatum, P. arrhenomanes, P. graminicola, P. intermedium, P. ultimum var. sporangiferum and Saprolegnia litoralis . The lytic compound, thought to be the saponin avenacin, was released from apparently undamaged oat roots. It prevented cyst wall formation by zoospores, but it was only weakly active or inactive against pre-encysted zoospores and vegetative mycelia of Pythium spp. Its effects on zoospores were paralleled by the saponin β-aescin. In preliminary tests, these compounds retained activity after passage through, or incubation in, soil.

A 2-yr study was conducted to evaluate the response of yellow starthistle density and grass biomass to combinations of newly seeded grass, picloram, and fertilizer. A combination of ‘Tualatin’ tall oatgrass or ‘Paiute’ orchardgrass with 0.14 or 0.28 kg ae/ha of picloram effectively controlled yellow starthistle and improved forage production. Grass seeded alone or combined with fertilizer neither controlled yellow starthistle nor improved forage production. Three-way combinations of grass, picloram, and fertilizer did not affect yellow starthistle density in either year but resulted in more ‘Tualatin’ tall oatgrass biomass in 1987.

SUMMARY The distribution and sequence of infection of grass and cereal hosts of ergot (Claviceps purpurea (Fr.) TuL) was observed during 1972–73 at a farm locality in Oxfordshire. Analysis of the alkaloid content of ergot sclerotia formed on these hosts indicated the presence of at least four distinct strains of the fungus which exhibited some host restriction. Strains parasitizing Lolium perenne, Dactylis glomerata, Holcus lanatus and Arrhenatherum elatius were, both on the evidence of the timing of natural infections and their sclerotial alkaloid content, of little importance in the aetiology of ergot disease of cereals. The qualitative spectrum of the major alkaloids was common to ergots collected from Alopecurus myosuroides, A. pratensis, wheat and barley. This supports the view that A. pratensis as a spring-flowering grass, and A. myosuroides as an early-flowering weed grass in cereal crops, may have important roles in the aetiology of ergot disease of cereals.

Summary A sodium bicarbonate concentration of 20 m-equiv./l brought about a partial inhibition of uptake of 59Fe by intact roots of Deschampsia flexuosa; subsequent translocation of the 59Fe to the shoots was also inhibited. A similar concentration of bicarbonate produced no inhibition of uptake by the related grasses Holcus mollis, Arrhenatherum elatius and Koeleria cristata. The amount of 59Fe translocated to the shoots in the course of the experiment was less than 1% of the amount of isotope which became associated with roots. Whilst the high uptake by the roots is suggestive of some absorption on the root surface there is evidence also of uptake, probably into a substantial pool of free iron within the root.

Summary The four grasses Deschampsia flexuosa, Holcus mollis, Arrhenatherum elatius and Koeleria gracilis grow on a wide range of soil types under natural conditions. Little is known of the physiological mechanisms by which the different species are adapted to particular soils. In glasshouse experiments all four species grew well on a fertile garden soil but showed varying diminution of growth on a calcareous soil, amounting in the extreme case of Deschampsia flexuosa to near failure, accompanied by chlorosis and severe inhibition of root development. The involvement of bicarbonate is suggested by the severe inhibition of growth of roots of D. flexuosa grown in water culture. Bicarbonate is without effect on the respiration of roots of the four species in short-term experiments but roots of D. flexuosa showed a much greater rate of 14C-bicarbonate fixation than the other species. It is suggested that the reduced growth of plants on calcareous soils may often be attributed to effects of bicarbonate on the physiology and growth of the root system leading only in extreme cases to chlorosis of the leaves. The data are discussed in relation to relevant physiological and ecological work. An appendix is added providing calculation of probable bicarbonate concentrations in calcareous soil solutions to provide a basis for the concentrations employed in laboratory studies.