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Roadside vegetation in Central Europe is mostly species‐poor and dominated by a few grass species. Hemiparasitic plant species, including Rhinanthus spp., might effectively restrict grass growth, thereby making space for light‐dependent herb species. Despite the significance of abiotic site conditions for plant establishment in general, their effects on Rhinanthus establishment are less well known. We investigated combined effects of water availability, litter amount and seed position within litter on Rhinanthus seedling emergence and growth.Two parallel greenhouse experiments were conducted with R. angustifolius and R. minor. In these, we tested the impact of 200 or 400 g litter·m−2 with seeds sown beneath or on top of a litter layer under constantly humid or intermittently dry conditions on seedling emergence and biomass production of Rhinanthus.Presence of litter positively affected Rhinanthus seedling emergence when sown beneath the litter layer and reduced negative effects of water deficiency. Sowing beneath a litter layer increased seedling emergence by 157%, with similar effects at 200 and 400 g litter·m−2. Water level did not affect biomass production. Compared to R. minor, R. angustifolius had higher mean biomass, and its seedlings emerged earlier and in higher numbers.Our results indicate that Rhinanthus spp. react similarly to litter as non‐hemiparasitic plant species from temperate grasslands. Litter presence positively influenced Rhinanthus seedling emergence and growth under intermittently dry conditions. Its hemiparasitic characteristics might reduce drought impacts on biomass production. To ensure seed contact with the soil surface, seeds should be sown when no litter is present, or mulching should occur post‐sowing. [ABSTRACT FROM AUTHOR]

Abstract Traditionally managed mesotrophic species‐rich upland hay meadows conforming to the National Vegetation Classification (NVC) MG3b are one of the rarest grassland types in the United Kingdom, with substantial declines in botanical diversity over the last 50 years. Intensive spring grazing, earlier cut dates and increases in soil fertility cause a decline in characteristic positive indicator species in MG3b meadows, shifting communities from species‐rich MG3b, to NVC MG6 meadows, and finally to species‐poor NVC MG7 meadows. The North Pennines Area of Outstanding Natural Beauty (AONB) Partnership's Hay Time project aimed to improve the knowledge of upland hay meadows, and to investigate the success of seed addition of key positive indicator species. A landscape‐scale restoration programme was undertaken between 2006 and 2012, harvesting seed from 82 species‐rich donor meadows and spreading seed onto 89 receptor meadows (222.82 ha). Seed was harvested as green hay, using two types of donors: MG6 (classed as restoration, with species such as Rhinanthus minor) and MG3b (classed as enhancement, with species such as Geranium sylvaticum). All 89 meadows were monitored, with a baseline botanical survey and a repeat survey 3–5 years after seed addition. In addition, 41 meadows that did not have seed addition were monitored (controls). Species richness, diversity and floristic composition improved in 77 meadows 3–5 years after seed addition. Eighteen plant species had an increase in frequency in the receptor meadows but did not increase in frequency in the control meadows. The most successful were eight positive indicators which were annuals or fast‐growing perennial plants (Anthoxanthum odoratum, Euphrasia spp., Myosotis discolor, Plantago lanceolata, Ranunculus acris, R minor, Trifolium dubium and Trifolium pratense). However, rarer characteristic MG3b plants such as Alchemilla spp., G. sylvaticum and Cirsium heterophyllum showed little signs of establishing. Botanical evidence is demonstrating that seed addition using green hay is a successful way of restoring meadows to an MG6 community. What is now needed is an effective method to establish characteristic MG3b plants. Hand‐collecting seeds and establishing plug plants, alongside seed addition and maintaining traditional management practises, is one possible way forward.

The root structure and the haustorial formation of 5 northern hemiparasites: Bartsia alpina, Castilleja lapponica, Pedicularis lapponica, Pedicularis sceptrum-carolinum, Rhinanthus minor subsp. groenlandicus (Orobanchaceae) have been studied. The autotroph Scrophularia nodosa (Scrophulariaceae) has been chosen as a control. It is shown that the main preconditions providing the possibility of rapid haustorium development are the long life of the primary outermost tissue of the root – the rhizodermis that covers the entire length of both young and older roots, and constant readiness of this tissue to form special haustorial hairs, and also an unusual structure of exodermis, which in many details is similar to rhizodermis. The formation of haustorial hairs is one of the earliest structural events in haustorium development; the haustorial hairs are long, with a smooth surface. The division and elongation of cells in the outer tissues play a major role in the early stages of endophyte development. The parasitic form of life influence the inner structure of the vascular cylinder that appears as the reduction of phloem conductive elements and the accumulation of large amounts of starch in the xylem. It was found that the haustoria can penetrate not only in the roots but also in the rhizomes of the host plants.

Summary: Species are commonly distributed along latitudinal and elevational gradients of growing season length to which they might respond via phenotypic plasticity and/or adaptive genetic differentiation. However, the relative contribution of these processes and whether plasticity, if it occurs, facilitates expansion along season‐length gradients remain unclear, but are important for predicting species fates during anthropogenic change.We quantified phenological trait variation in the montane annual Rhinanthus minor for three generations at 12 sites across 900 m of elevation in the Canadian Rocky Mountains and conducted a reciprocal transplant experiment for two generations among nine sites. We compared clines and interannual variation of phenological traits between natural and transplanted individuals.Season length declined by c. 37% along our elevational gradient and, as expected, plants emerged, reached first flower and made their first seed in c. 41% fewer growing degree days under shorter growing seasons. Although reciprocal transplants revealed modest genetic differentiation across elevation, trait clines primarily were due to striking co‐gradient plasticity that paralleled genetic differentiation.Co‐gradient plasticity likely evolved in response to considerable interannual variation in season length across our elevational transect, and should prepare R. minor to make adaptive changes to phenology in response to ongoing climate change predicted for montane environments. See also the Commentary on this article by Wadgymar & Austen, 224: 1009–1011. [ABSTRACT FROM AUTHOR]

According to theory, edge populations may be poised to expand species' ranges if they are locally adapted to extreme conditions, or ill‐suited to colonise beyond‐range habitat if their offspring are genetically and competitively inferior. We tested these contrasting predictions by transplanting low‐, mid‐, and high‐elevation (edge) populations of an annual plant throughout and above its elevational distribution. Seed from poor‐quality edge habitat (one of two transects) had inferior emergence, but edge seeds also had adaptive phenology (both transects). High‐elevation plants flowered earlier, required less heat accumulation to mature seed, and so achieved higher lifetime fitness at and above the range edge. Experimental warming improved fitness above the range, but eliminated the advantage of local cold‐edge populations, supporting recent models in which cold‐adapted edge populations do not facilitate warming‐induced range shifts. The highest above‐range fitness was achieved by a 'super edge phenotype' from a neighbouring mountain, suggesting key adaptations exist regionally even if absent from local edge populations. [ABSTRACT FROM AUTHOR]

Direct and indirect biotic interactions may affect plant growth and development, but the magnitude of these effects may vary depending on environmental conditions. In grassland ecosystems, competition is a strong structuring force. Nonetheless, if hemiparasitic plant species are introduced the competition intensity caused by the dominant species may be affected. However, the outcome of these interactions may change between wet or dry periods. In order to study this, we performed a pot experiment with different densities of the dominant species Schedonorus arundinaceus (1, 2 or 4 individuals) under constantly moist or intermittently dry conditions. The different Schenodorus densities were crossed with presence or absence of hemiparasites (either Rhinanthus minor or R. alectorolophus). Additionally, pots remained with bare ground or received a grass litter layer (400 g m). We expected that indirect litter effects on vegetation (here Schedonorus or Rhinanthus) vary depending on soil moisture. We measured Schedonorus and Rhinanthus aboveground biomass and C stable isotope signature (δC) as response variables. Overall, Schedonorus attained similar biomass under moist conditions with Rhinanthus as in pots under dry conditions without Rhinanthus. Presence of Rhinanthus also increased δC in moist pots, indicating hemiparasite-induced water stress. Litter presence increased Schedonorus biomass and reduced δC, indicating improved water availability. Plants under dry conditions with litter showed similar biomass as under wet conditions without litter. Hemiparasites and litter had opposite effects: hemiparasites reduced Schedonorus biomass while litter presence facilitated grass growth. Contrary to our expectations, litter did not compensate Schedonorus biomass when Rhinanthus was present. [ABSTRACT FROM AUTHOR]

In the UK, upland hay meadows ( Anthoxanthum odoratum-Geranium sylvaticum grassland) with high plant biodiversity are rare and confined to submontane areas of northern England. We report results from a 5-year experiment to test suggestions that recent biodiversity declines were attributable to increased sheep-stocking density and a longer spring stocking period, thus delaying the shut up date for the growth of the hay crop. Longer stocking periods and higher stocking densities decreased the forage mass at 8 July, but they increased herbage N content and digestibility, reduced plant species diversity and reduced populations and seed production of Rhinanthus minor. Compared with unstocked swards, the similarity of the vegetation to Anthoxanthum odoratum-Geranium sylvaticum grassland was reduced by 16·9% when stocking with sheep continued until 27 May each year, and by 8·3% when sward heights were maintained at 3 cm compared with 5 cm. Increased mean sward height and height of R. minor were positively correlated with accumulated temperatures. Results support suggestions that recent reductions in the nature value of these grasslands might be a consequence of high stocking densities persisting until later in the spring, carried out during a 1-year period with warmer temperatures. [ABSTRACT FROM AUTHOR]

Root hemiparasites are green plants which attach to roots of other plants and extract solutes from the host-root xylem parasitically. They frequently act as keystone species by affecting competitive relations in plant communities and altering mineral nutrient cycling. Understanding their ecology has been hindered by the difficulty to identify host associations of hemiparasitic plants growing in natural conditions. Direct examination of host associations is only possible at sites with specific soil types (e.g. sandy substrates) that allow host roots to be traced to the shoot to identify the host species. We investigated the possibility of using a DNA barcoding-based approach to identify host associations of root hemiparasites growing naturally. Host associations of Melampyrum nemorosum, Rhinanthus major and Rhinanthus minor were investigated. Their root systems were washed free of soil to reveal haustorial connections. Host-root fragments were subjected to DNA extraction and the plastid DNA trnL intron was sequenced. The functioning of haustoria was examined in semi-thin anatomical sections. The analysis of the DNA of host roots yielded a ca 60% success rate. The Rhinanthus species were confirmed to attack mostly grasses and legumes. By contrast, Melampyrum nemorosum attached mainly to plants of Rosaceae and Asteraceae. In addition, both conspecific and heterospecific connections between the hemiparasites were frequently observed. Our study demonstrates the usefulness of the DNA barcoding approach for identifying host associations of root hemiparasites at sites where tracing host roots to their shoot is not possible due to soil structure or high rooting density. [ABSTRACT FROM AUTHOR]

When parasitic plants and aphid herbivores share a host, both direct and indirect ecological effects (IEEs) can influence evolutionary processes. We used a hemiparasitic plant (Rhinanthus minor), a grass host (Hordeum vulgare) and a cereal aphid (Sitobion avenae) to investigate the genetics of IEEs between the aphid and the parasitic plant, and looked to see how these might affect or be influenced by the genetic diversity of the host plants. Survival of R. minor depended on the parasite’s population of origin, the genotypes of the aphids sharing the host and the genetic diversity in the host plant community. Hence the indirect effects of the aphids on the parasitic plants depended on the genetic environment of the system. Here, we show that genetic variation can be important in determining the outcome of IEEs. Therefore, IEEs have the potential to influence evolutionary processes and the continuity of species interactions over time.

Understanding the impact of species on community structure is a fundamental question in ecology. There is a growing body of evidence that suggests that both subdominant species and parasites can have disproportionately large effects on other organisms. Here we report those impacts for a species that is both subdominant and parasitic, the hemiparasite Rhinanthus minor. While the impact of parasitic angiosperms on their hosts and, to a lesser degree, coexisting plant species, has been well characterized, much less is known about their effects on higher trophic levels. We experimentally manipulated field densities of the hemiparasite Rhinanthus minor in a species-rich grassland, comparing the plant and invertebrate communities in plots where it was removed, present at natural densities, or present at enhanced densities. Plots with natural and enhanced densities of R. minor had lower plant biomass than plots without the hemiparasite, but enhanced densities almost doubled the abundance of invertebrates within the plots across all trophic levels, with effects evident in herbivores, predators, and detritivores. The hemiparasite R. minor, despite being a subdominant and transient component within plant communities that it inhabits, has profound effects on four different trophic levels. These effects persist beyond the life of the hemiparasite, emphasizing its role as a keystone species in grassland communities. [ABSTRACT FROM AUTHOR]

Background and Aims Parasitic plants obtain nutrients from their hosts through organs called haustoria. The hyaline body is a specialized parenchymatous tissue occupying the central parts of haustoria in many Orobanchaceae species. The structure and functions of hyaline bodies are poorly understood despite their apparent necessity for the proper functioning of haustoria. Reported here is a cell wall-focused immunohistochemical study of the hyaline bodies of three species from the ecologically important clade of rhinanthoid Orobanchaceae. Methods Haustoria collected from laboratory-grown and field-collected plants of Rhinanthus minor, Odontites vernus and Melampyrum pratense attached to various hosts were immunolabelled for cell wall matrix glycans and glycoproteins using specific monoclonal antibodies (mAbs). Key Results Hyaline body cell wall architecture differed from that of the surrounding parenchyma in all species investigated. Enrichment in arabinogalactan protein (AGP) epitopes labelled with mAbs LM2, JIM8, JIM13, JIM14 and CCRC-M7 was prominent and coincided with reduced labelling of de-esterified homogalacturonan with mAbs JIM5, LM18 and LM19. Furthermore, paramural bodies, intercellular deposits and globular ergastic bodies composed of pectins, xyloglucans, extensins and AGPs were common. In Rhinanthus they were particularly abundant in pairings with legume hosts. Hyaline body cells were not in direct contact with haustorial xylem, which was surrounded by a single layer of paratracheal parenchyma with thickened cell walls abutting the xylem. Conclusions The distinctive anatomy and cell wall architecture indicate hyaline body specialization. Altered proportions of AGPs and pectins may affect the mechanical properties of hyaline body cell walls. This and the association with a transfer-like type of paratracheal parenchyma suggest a role in nutrient translocation. Organelle-rich protoplasts and the presence of exceptionally profuse intra- and intercellular wall materials when attached to a nitrogen-fixing host suggest subsequent processing and transient storage of nutrients. AGPs might therefore be implicated in nutrient transfer and metabolism in haustoria. [ABSTRACT FROM PUBLISHER]

The exploitation of shared resources by diverse organisms underpins the structure of ecological communities. Hemiparasitic plants and the insect herbivores feeding on them both rely, directly and indirectly, on the resources supplied by the parasite's host plant. Therefore, the identity and number of host plant species providing these resources is likely to be critical for parasite and herbivore performance., We tested the effect of single and multiple host species on the biomass of the generalist parasitic plant Rhinanthus minor and the abundance of its aphid ( Aphis gossypii) herbivores., Parasite biomass was proportional to the number of haustorial connections to host roots and was determined by host species identity rather than host functional group. Host species identity was also an important influence on aphid population size, and parasites attached to Lotus corniculatus experienced a considerable reduction in aphid herbivory., The effects on the parasite attaching to multiple hosts depended on the combination of species present. However, host mixtures generally benefitted aphids by diluting the negative effects of particular host species., Our findings suggest that the specificity of host attachment alters the impact of this keystone parasitic plant on its own herbivores and, potentially, on the wider plant and herbivore community. [ABSTRACT FROM AUTHOR]

Parasitic plants have major impacts on plant community structure through their direct negative influence on host productivity and competitive ability. However, the possibility that these parasites may also have indirect impacts on community structure (via the mechanism of nutrient-rich litter input) while long hypothesized, has remained unsupported until now., Using the hemiparasite Rhinanthus minor, we established experimental grassland mesocosms to quantify the impacts of Rhinanthus litter and parasitism across two soil fertility levels. We measured the biomass and tissue nutrient concentration of three functional groups within these communities to determine their physiological response to resource abstraction and litter input by the parasite., We show that Rhinanthus alters the biomass and nutrient status of co-occurring plants with contrasting effects on different functional groups via the mechanism of nutrient-rich litter input. Critically, in the case of grass and total community biomass, this partially negates biomass reductions caused directly by parasitism., This demonstrates that the influence of parasitic plant litter on plant community structure can be of equal importance to the much-reported direct impacts of parasitism. We must consider both positive indirect (litter) and negative direct (parasitism) impacts of parasitic plants to understand their role in structuring plant communities. [ABSTRACT FROM AUTHOR]

Abstract: In the last few decades unimproved semi-natural grasslands have been affected by intensification of land use and habitat fragmentation. Because of their biodiversity these species-rich grasslands are of high conservation importance and efforts are under way to restore such habitats. Detailed knowledge of within species diversity will aid deciding on the optimal seed source for such restoration projects, e.g. local genotypes or ecotypes. Rhinanthus minor is a species that is typically found in semi-natural grasslands and is commonly used in grassland restoration projects. This is because R. minor is a hemiparasitic plant that takes minerals and nutrients from its host, which in turn decreases the host''s biomass and leads to opportunities for less competitive species in the vegetation. Here, we investigate genetic diversity within and between R. minor populations. This allowed us to test whether the six different subspecies of R. minor that have been described in the UK, based on their morphology, flowering time, and habitat, can be differentiated using molecular markers. We identified moderate levels of genetic differentiation between R. minor populations within the UK. In addition, R. minor individuals from the UK appear to be distinct from R. minor and Rhinanthus angustifolius individuals from other European countries based on microsatellite genotyping and DNA sequencing of cpDNA and rDNA ITS. The molecular markers used in the current study did not separate populations of R. minor based on either their subspecies or habitat. The implication for the use of R. minor in grassland restoration projects seems to be that it is not necessary to use local seeds or seeds from the same subspecies. [Copyright &y& Elsevier]

Premise of the study: Several barriers against hybrid formation exist, and their combined action can affect the evolutionary outcomes of hybridization. To explain the asymmetrical introgression observed between two bumblebee-pollinated plant species (Rhinanthus angustifolius and R. minor), we focused on post-pollination barriers and ethological isolation of hybrids. Methods: We studied pollen competition in conspecific and heterospecific crosses on both species and analyzed germination rates of hybrid and pure seeds. We also measured bumblebee visitation rates to hybrids relative to their parents using potted Rhinanthus placed in populations of each parental species. Key results: In mixed pollinations, there was a conspecific siring advantage in both species, but no difference in pollen tube growth rates in either cross type. F1 seeds with a R. angustifolius maternal plant germinated poorly, while those with R. minor as the maternal parent germinated better than pure seeds. Interestingly, bumblebees treated hybrids almost as equal to the background species and more often rejected the nonresident Rhinanthus. In a R. angustifolius background, bumblebees preferred R. angustifolius, but visited hybrids more often than R. minor. In contrast, visitation rates were similar on a R. minor background. Conclusions: Our results suggest that hybridization rates in Rhinanthus remain low because of several leaky barriers that make R. minor the maternal parent of most F1 offspring. Preference for R. angustifolius and the equal treatment of F1 and background species by bumblebees induce a visitation pattern that directs gene flow toward R. angustifolius when this species predominates. [ABSTRACT FROM AUTHOR]

Northern hemispheric background concentrations of ozone are increasing, but few studies have assessed the ecological significance of these changes for grasslands of high conservation value under field conditions. We carried out a 3-year field experiment in which ozone was released at a controlled rate over three experimental transects to produce concentration gradients over the field site, an upland mesotrophic grassland located in the UK. We measured individual species biomass in an annual hay cut in plots receiving ambient ozone, and ambient ozone elevated by mean concentrations of approximately 4 ppb and 10 ppb in the growing seasons of 2008 and 2009. There was a significant negative effect of ozone exposure on herb biomass, but not total grass or legume biomass, in 2008 and 2009. Within the herb fraction, ozone exposure significantly decreased the biomass of Ranunculus species and that of the hemi-parasitic species Rhinanthus minor. Multivariate analysis of species composition, taking into account spatial variation in soil conditions and ozone exposure, showed no significant ozone effect on the grass component. In contrast, by 2009, ozone had become the dominant factor influencing species composition within the combined herb and legume component. Our results suggest that elevated ozone concentrations may be a significant barrier to achieving increased species diversity in managed grasslands. [ABSTRACT FROM AUTHOR]

Copyright of Basic & Applied Ecology is the property of Urban & Fischer Verlag and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

the ecological level, the effects of the facultative root hemiparasite Rhinanthus minor on the structure and functioning of its host communities are relative well described; yet until recently, the mechanistic basis for parasitic plant-driven community change and the physiological basis for the host-parasite interaction were poorly understood. Empirical incremental flow models, based on the increase in water, mineral nutrients, carbon assimilates or phytohormones between two defined time points, have been successfully employed to investigate the physiology of resource acquisition by- and distribution within host-parasitic plant associations. In this study we review the application of these empirical flow models to Rhinanthus-host associations showing the extent of and physiological basis of resource abstraction from the host and how this is profoundly influenced by soil nutrient status. We show that Rhinanthus primarily abstracts water and mineral nutrients via the apoplastic pathway through direct lumen-lumen connections with little resource acquisition via symplastic pathways. Nutrient status of the soil is shown to significantly influence the resource acquisition. We also investigate the hormonal regulation of resource acquisition by Rhinanthus showing pivotal roles for the key for the phytohormones abscisic acid (ABA) and cytokinins. [ABSTRACT FROM AUTHOR]

Plant communities can be affected both by arbuscular mycorrhizal fungi (AMF) and hemiparasitic plants. However, little is known about the interactive effects of these two biotic factors on the productivity and diversity of plant communities. To address this question, we set up a greenhouse study in which different AMF inocula and a hemiparasitic plant ( Rhinanthus minor) were added to experimental grassland communities in a fully factorial design. In addition, single plants of each species in the grassland community were grown with the same treatments to distinguish direct AMF effects from indirect effects via plant competition. We found that AMF changed plant community structure by influencing the plant species differently. At the community level, AMF decreased the productivity by 15–24%, depending on the particular AMF treatment, mainly because two dominant species, Holcus lanatus and Plantago lanceolata, showed a negative mycorrhizal dependency. Concomitantly, plant diversity increased due to AMF inoculation and was highest in the treatment with a combination of two commercial AM strains. AMF had a positive effect on growth of the hemiparasite, and thereby induced a negative impact of the hemiparasite on host plant biomass which was not found in non-inoculated communities. However, the hemiparasite did not increase plant diversity. Our results highlight the importance of interactions with soil microbes for plant community structure and that these indirect effects can vary among AMF treatments. We conclude that mutualistic interactions with AMF, but not antagonistic interactions with a root hemiparasite, promote plant diversity in this grassland community. [ABSTRACT FROM AUTHOR]

Copyright of Basic & Applied Ecology is the property of Urban & Fischer Verlag and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article examines the effectiveness of a simple plant population spread model which uses field data on demography and dispersal for four management systems, in measuring the population spread in the herb, Rhinanthus minor. It also explores the effectiveness of the model in predicting the impacts of the management strategies: grazed only (GR), hay-cut once (H1), hay-cut twice (H2) and hay-cut with autumn grazing (HG), in the population spread rates of Rhinanthus. Results show that simple models, like the one used in this study, are effective means of informing practical plant conservation management as well as in predicting the impact of different plant management strategies.

Upland hay meadows conforming to MG3 in the National Vegetation Classification of the UK are a rare habitat in Britain and are largely confined to upland valleys in northern England. Agricultural intensification, particularly ploughing and reseeding and a shift from hay-making to silage production over the last 50 years, has resulted in large losses of species-rich upland hay meadows. Remaining species-rich meadows have been the focus of much nature conservation effort resulting in many of the species-rich sites being protected by statutory designations or through voluntary agri-environment scheme agreements. Research and monitoring has tended to confirm that species richness is maximized by management involving spring and autumn grazing, a mid-July hay cut, no inorganic fertilizer and possibly low levels of farmyard manure. Deviations from this regime result in a loss of species richness. Restoration of semi-improved grassland to swards resembling species-rich MG3 also requires a similar regime but is also dependent on the introduction of seed of appropriate species. The role of Rhinanthus minor as a tool for manipulating meadow biodiversity during restoration management is discussed. Suggestions for future research are outlined. [ABSTRACT FROM AUTHOR]

Using the facultative root hemiparasite Rhinanthus minor and Hordeum vulgare as a host, the flows and partitioning of mannitol in the parasite, and of sucrose in the host have been studied during the period of 41 to 54 days after planting, i.e, about 30 to 43 days after successful attachment of the parasite to the host. The biosynthesis of mannitol in Rhinanthus shoots increased 16-fold by parasitism, resulting in a 15-fold higher mannitol flow in the phloem and a 10-fold higher deposition in the shoot. Under reduced nitrogen supply and with ammonium as the only N-form the concentrations of mannitol tended to be increased by approximately 2-fold. Xylem flows of mannitol were increased 10-fold after attachment. No mannitol was found in barley roots even in the direct vicinity of the haustoria. Compared to unparasitized barley, the net biosynthesis and deposition in the shoot and the phloem flow was decreased substantially. No sucrose has been detected in barley xylem sap and consequently there was no indication of a sucrose transfer from the host to the parasite. A possible involvement of mannitol in the abscisic acid relations of the parasite is discussed. [ABSTRACT FROM AUTHOR]

Using the facultative root hemiparasite Rhinanthus minor and Hordeum vulgare as a host, the flows, depositions, and metabolism of abscisic acid (ABA) within the host, within the parasite, and between host and parasite have been studied. When the plants were supplied with 5 mM NO3−, there were weak or no effects of parasitism on ABA flows, biosynthesis, and ABA degradation in barley. However, ABA deposition was significantly affected in the leaf laminae (3-fold) and in the leaf sheath (2.4-fold), but not in roots. Dramatic changes in ABA flows, metabolism, and deposition on a per plant basis, however, have been observed in Rhinanthus. Biosynthesis in the roots was 12-fold higher after attachment, resulting in 14-fold higher ABA flows in the xylem. A large portion of this ABA was metabolized, a small portion was deposited. Phloem flows of ABA were increased 13-fold after attachment. The concentrations of ABA in tissues and transport fluids were higher in attached Rhinanthus by an order of magnitude than in host tissues and xylem sap. The same tendency was also found in a comparison between single Rhinanthus and unparasitized barley. As compared with 5 mM NO3−, lower NO3− or 1 mM NH4+ supply doubled the ABA concentrations in barley leaf laminae, while having only small or non-significant effects in the other organs. The possible function of ABA for the parasite is discussed. [ABSTRACT FROM PUBLISHER]

Question: The optimal use of the point intercept method (PIM) for efficient estimation of plant biomass has not been addressed although PIM is a commonly used method in vegetation analysis. In this study we compare results achieved using PIM at a range of efforts, we assess a method for calculating these results that are new with PIM and we provide a formula for planning the optimal use of PIM. Location: Northern Norway. Methods: We collected intercept data at a range of efforts, i.e. from one to 100 pins per 0.25 m² plots, on three plant growth forms in a mountain meadow. After collection of intercept data we clipped and weighed the plant biomass. The relationship between intercept frequency and weighed biomass (b) was estimated using both a weighted linear regression model (WLR) and an ordinary linear regression model (OLR). The accuracy of the estimate of biomass achieved by PIM at different efforts was assessed by running computer simulations at different pin densities. Results: The relationship between intercept frequency and weighed biomass (b) was far better estimated using WLR compared to the normally used OLR. Efforts above 10 pins per 0.25 m² plot had a negligible effect on the accuracy of the estimate of biomass achieved by PIM whereas the number of plots had a strong effect. Moreover, for a given level of accuracy, the required number of plots varied depending on plant growth form. We achieved similar results to that of the computer simulations when applying our WLR based formula. Conclusion: This study shows that PIM can be applied more efficiently than was done in previous studies for the purpose of plant biomass estimation, where several plots should be analysed but at considerably less effort per plot. Moreover, WLR rather than OLR should be applied when estimating biomass from intercept frequency. The formula we have deduced is a useful tool for planning plant biomass analysis with PIM. [ABSTRACT FROM AUTHOR]

The effects of elevated CO2 (650 ppm) on interactions between a chlorophyllous parasitic angiosperm, Rhinanthus minor (L.) and a host, Poa pratensis (L.) were investigated. R. minor benefited from elevated CO2, with both photosynthesis and biomass increasing, and transpiration and tissue N concentration remaining unaffected. However, this did not alleviate the negative effect of the parasite on the host; R. minor reduced host photosynthesis, transpiration, leaf area and biomass, irrespective of CO2 concentration. Elevated CO2 resulted in increased host photosynthesis, but there was no concomitant increase in biomass and foliar N decreased. It appears that the parasite may reduce host growth more by competition for nitrogen than for carbon. Contrary to expectation, R. minor did not reduce the productivity of the host–parasite association, and it actually contributed to the stimulation of productivity of the association by elevated CO2. [ABSTRACT FROM PUBLISHER]

We studied the effect of light availability on the growth of an angiospermatic root hemiparasite, Rhinanthus minor. When attached to its host, height growth increased in response to shading, demonstrating that R. minor was able to detect alterations in light quality and/or quantity. However, this reduced illumination did not affect its biomass, number of haustoria, or the amount of15N transferred from the hosts, compared with its performance under non-shaded conditions. Therefore, R. minor is unlikely to have difficulty in extracting host resources under shading. This result may have been mediated by a lowered R. minor transpiration rate in response to fluctuations in external conditions, including shading and water stress, compared with non-parasitic plants. Therefore, we suggest that, as long as the extent of resources diverted from host to parasite is not significantly altered by shading, growth of the attached R. minor will be unaffected by reduced light availability per se. [ABSTRACT FROM AUTHOR]

Little research has been carried out on the genetics of Rhinanthus minor to date. To enable study of this species, eight polymorphic microsatellite loci were developed, using a genomic library enriched for microsatellites. All loci are polymorphic in the two UK populations tested, Bardister and Oxwich Bay. These microsatellite markers will be useful for studying genetic structure and subspecies differences of R. minor. [ABSTRACT FROM AUTHOR]