Potentilla Reptans Research Articles

Testing for disconnection and distance effects on physiological self-recognition within clonal fragments of Potentilla reptans.

Evidence suggests that belowground self-recognition in clonal plants can be disrupted between sister ramets by the loss of connections or long distances within a genet. However, these results may be confounded by severing connections between ramets in the setups. Using Potentilla reptans, we examined severance effects in a setup that grew ramet pairs with connections either intact or severed. We showed that severance generally reduced new stolon mass but had no effect on root allocation of ramets. However, it did reduce root mass of younger ramets of the pairs. We also explored evidence for physiological self-recognition with another setup that avoided severing connections by manipulating root interactions between closely connected ramets, between remotely connected ramets and between disconnected ramets within one genet. We found that ramets grown with disconnected neighbors had less new stolon mass, similar root mass but higher root allocation as compared to ramets grown with connected neighbors. There was no difference in ramet growth between closely connected- and remotely connected-neighbor treatments. We suggest that severing connections affects ramet interactions by disrupting their physiological integration. Using the second setup, we provide unbiased evidence for physiological self-recognition, while also suggesting that it can persist over long distances.

Medicinal plants used for cardiovascular diseases in Navarra and their validation from Official sources

Ethnopharmacological relevanceThis paper provides significant ethnopharmacological information on plants used to treat cardiovascular diseases in Navarra, Spain. Material and methodsInformation was collected using semi-structured ethnobotanical interviews with 667 informants (mean age 72; 55.47% women, 44.53% men) in 265 locations. Official sources such as the European Scientific Cooperative on Phytotherapy (ESCOP), German Commission E, World Health Organization (WHO), European Medicines Agency (EMA), European Pharmacopoeia (Ph. Eur.) and Real Farmacopea Española (RFE) monographs were consulted in order to establish the therapeutic efficacy of the reported uses and to obtain further details about quality and safety aspects. A literature review was carried out on the plants that were most frequently cited and were not the subject of a monograph, using a new tool developed by the University of Navarra, UNIKA. ResultsA total of 460 pharmaceutical uses were reported by the informants, belonging to 90 plant species and 39 families, mainly represented by Urticaceae, Rosaceae, Asteraceae, and Equisetaceae. The most frequently used parts of the plants were the aerial parts followed by leaves and flowers. Seventeen out of 90 plants (19%) and 208 out of 460 popular uses (45%) had already been pharmacologically validated in relation to their therapeutic efficacy and safety aspects. ConclusionsThe authors propose to validate five species for their use in cardiovascular diseases: Rhamnus alaternus L., Potentilla reptans L., Equisetum telmateia Ehrh., Centaurium erythraea Rafn and Parietaria judaica L.

Competition and facilitation among plants for pollination: can pollinator abundance shift the plant–plant interactions?

We hypothesize interactions among plants for pollination may depend on pollinator abundance, which always varies among years and habitats and has different effects on plant reproductive success. Honeybee-pollinated plants, Lotus corniculatus, and its commonly coflowering neighbor, Potentilla reptans var. sericophylla, were used in a two-year project. We designed six types of plant combinations with different conspecific and interspecific flower densities in 2011 and repeated this in the same site in 2012. Meanwhile, we artificially increased pollinator abundance by hiring beehives only in 2011. Pollinator abundance as well as flower density significantly affected pollination of L. corniculatus plants from both the conspecific and interspecific plots. Total number of bees visiting a plot was enhanced by an increase in both the conspecific and interspecific flower densities regardless of high or low pollinator abundance. However, changes in visitation rates and fruit sets in the focal plants when flower densities were increased depended on pollinator abundance. Under high pollinator abundance, an increase in both the conspecific and interspecific flower densities significantly enhanced pollinator visits to L. corniculatus. However, under low pollinator abundance, the pollinator visitation rate remained unchanged as conspecific flower density increased, but decreased when there was an increase in interspecific flower density. Coflowering plants enhanced fruit sets of L. corniculatus only when the pollinator abundance was high. The findings suggest that the interactions among plants for pollination are influenced not only by a plant density threshold, but also by a pollinator abundance threshold.

Root Foraging Increases Performance of the Clonal Plant Potentilla reptans in Heterogeneous Nutrient Environments

BackgroundPlastic root-foraging responses have been widely recognized as an important strategy for plants to explore heterogeneously distributed resources. However, the benefits and costs of root foraging have received little attention.Methodology/Principal FindingsIn a greenhouse experiment, we grew pairs of connected ramets of 22 genotypes of the stoloniferous plant Potentilla reptans in paired pots, between which the contrast in nutrient availability was set as null, medium and high, but with the total nutrient amount kept the same. We calculated root-foraging intensity of each individual ramet pair as the difference in root mass between paired ramets divided by the total root mass. For each genotype, we then calculated root-foraging ability as the slope of the regression of root-foraging intensity against patch contrast. For all genotypes, root-foraging intensity increased with patch contrast and the total biomass and number of offspring ramets were lowest at high patch contrast. Among genotypes, root-foraging intensity was positively related to production of offspring ramets and biomass in the high patch-contrast treatment, which indicates an evolutionary benefit of root foraging in heterogeneous environments. However, we found no significant evidence that the ability of plastic foraging imposes costs under homogeneous conditions (i.e. when foraging is not needed).Conclusions/SignificanceOur results show that plants of P. reptans adjust their root-foraging intensity according to patch contrast. Moreover, the results show that the root foraging has an evolutionary advantage in heterogeneous environments, while costs of having the ability of plastic root foraging were absent or very small.

Whole-canopy carbon gain as a result of selection on individual performance of ten genotypes of a clonal plant

Game theoretical models predict that plant competition for light leads to reduced productivity of vegetation stands through selection for traits that maximize carbon gains of individuals. Using empirical results from a 5-year competition experiment with 10 genotypes of the clonal plant Potentilla reptans, we tested this prediction by analyzing the effects of the existing leaf area values on the carbon gain of the different genotypes and the consequent whole canopy carbon gain. We focused on specific leaf area (SLA) due to its role in the trade-off between light capture area and photosynthetic capacity per unit area. By combining a canopy model based on measured leaf area and light profiles with a game theoretical approach, we analyzed how changes in the SLA affected genotypic and whole-stand carbon gain. This showed that all genotypes contributed to reduced stand productivity. The dominant genotype maximized its share of total carbon gain, resulting in lower than maximal absolute gain. Other genotypes did not maximize their share. Hypothetical mutants of the dominant genotype were not able to achieve a higher carbon gain. Conversely, in other genotypes, some mutations did result in increased carbon gain. Hence, genotypic differences in the ability to maximize performance may determine genotype frequency. It shows how genotypic selection may result in lower carbon gains of the whole vegetation, and of the individual genotypes it consists of, through similar mechanisms as those that lead to the tragedy of the commons.

Antimicrobial assays of three native British plants used in Anglo-Saxon medicine for wound healing formulations in 10th century England

Ethnopharmacological relevanceThree important Anglo-Saxon medical texts from the 10th century contain herbal formulations for over 250 plant species, many of which have yet to be evaluated for their phytochemical and/or pharmacological properties. In this study, three native British plants were selected to determine antimicrobial activity relevant to treating bacterial infections and wounds. Materials and methodsSeveral preparations of Agrimonia eupatoria L., Arctium minus (Hill) Bernh. and Potentilla reptans L. were screened for antimicrobial activity against selected Gram-positive and Gram-negative bacteria of relevance in wounds using a 96 well plate microdilution method (200, 40 and 8μg/mL). Minimum inhibitory concentration (MIC) values were determined for the most potent extracts from 2 to 0.004mg/mL and HPLC chromatograms examined by multivariate analysis. Principle components analysis (PCA) was used to identify chemical differences between antimicrobial activity of the crude extracts. ResultsThe HPLC–PCA score plots attributed HPLC peaks to the antimicrobial activity with all three plants inhibiting growth of Gram-positive Staphylococcus aureus by >50% in four or more extracts. The first two principal components (PC) represented 87% of the dataset variance. The P. reptans 75% ethanol root extract exhibited the greatest range of activity with MIC50 at 31.25μg/mL to a total MIC that was also the minimum bactericidal concentration (MBC) at 1mg/mL. Additionally, the root of P. reptans, inhibited growth of Gram-negative bacteria with the 75% ethanol extract having a MIC50 at 1mg/mL against Pseudomonas aeruginosa and the decoction a MIC50 at 3.9μg/mL against Escherichia coli. ConclusionsThe results indicate a moderate antimicrobial activity against common wound pathogens for P. reptans suggesting it may well have been effective for treating wound and bacterial infections. Anglo-Saxon literary heritage may provide a credible basis for researching new antimicrobial formulations. Our approach encompassing advanced analytical technologies and chemometric models paves the way for systematic investigation of Anglo-Saxon medical literature for further therapeutic indications to uncover knowledge of native British plants, some of which are currently lost to modern Western herbal medicine.

How past and present influence the foraging of clonal plants?

Clonal plants spreading horizontally and forming a network structure of ramets exhibit complex growth patterns to maximize resource uptake from the environment. They respond to spatial heterogeneity by changing their internode length or branching frequency. Ramets definitively root in the soil but stay interconnected for a varying period of time thus allowing an exchange of spatial and temporal information. We quantified the foraging response of clonal plants depending on the local soil quality sampled by the rooting ramet (i.e. the present information) and the resource variability sampled by the older ramets (i.e. the past information). We demonstrated that two related species, Potentilla reptans and P. anserina, responded similarly to the local quality of their environment by decreasing their internode length in response to nutrient-rich soil. Only P. reptans responded to resource variability by decreasing its internode length. In both species, the experience acquired by older ramets influenced the plastic response of new rooted ramets: the internode length between ramets depended not only on the soil quality locally sampled but also on the soil quality previously sampled by older ramets. We quantified the effect of the information perceived at different time and space on the foraging behavior of clonal plants by showing a non-linear response of the ramet rooting in the soil of a given quality. These data suggest that the decision to grow a stolon or to root a ramet at a given distance from the older ramet results from the integration of the past and present information about the richness and the variability of the environment.

Poster #243 THE BRAIN-GUT CONNECTION: CONSTIPATION IN SCHIZOPHRENIA

Three important Anglo-Saxon medical texts from the 10th century contain herbal formulations for over 250 plant species, many of which have yet to be evaluated for their phytochemical and/or pharmacological properties. In this study, three native British plants were selected to determine antimicrobial activity relevant to treating bacterial infections and wounds.Several preparations of Agrimonia eupatoria L., Arctium minus (Hill) Bernh. and Potentilla reptans L. were screened for antimicrobial activity against selected Gram-positive and Gram-negative bacteria of relevance in wounds using a 96 well plate microdilution method (200, 40 and 8 μg/mL). Minimum inhibitory concentration (MIC) values were determined for the most potent extracts from 2 to 0.004 mg/mL and HPLC chromatograms examined by multivariate analysis. Principle components analysis (PCA) was used to identify chemical differences between antimicrobial activity of the crude extracts.The HPLC–PCA score plots attributed HPLC peaks to the antimicrobial activity with all three plants inhibiting growth of Gram-positive Staphylococcus aureus by >50% in four or more extracts. The first two principal components (PC) represented 87% of the dataset variance. The P. reptans 75% ethanol root extract exhibited the greatest range of activity with MIC50 at 31.25 μg/mL to a total MIC that was also the minimum bactericidal concentration (MBC) at 1 mg/mL. Additionally, the root of P. reptans, inhibited growth of Gram-negative bacteria with the 75% ethanol extract having a MIC50 at 1 mg/mL against Pseudomonas aeruginosa and the decoction a MIC50 at 3.9 μg/mL against Escherichia coli.The results indicate a moderate antimicrobial activity against common wound pathogens for P. reptans suggesting it may well have been effective for treating wound and bacterial infections. Anglo-Saxon literary heritage may provide a credible basis for researching new antimicrobial formulations. Our approach encompassing advanced analytical technologies and chemometric models paves the way for systematic investigation of Anglo-Saxon medical literature for further therapeutic indications to uncover knowledge of native British plants, some of which are currently lost to modern Western herbal medicine.

Entomological and functional role of floral strips in an organic apple orchard: Hymenopteran parasitoids as a case study

Habitat manipulation techniques improve the availability of resources required by natural enemies to increase their effectiveness. This study focused on the effects of floral strips on Hymenopteran parasitoid presence. The experiments were conducted during spring 2007 in one organic low-input apple orchard located in south-eastern France. The density and the diversity of parasitic wasps collected from sown floral strips were higher than those from mown plants. The family of parasitic wasps of Braconidae was strongly dominant, followed by Mymaridae and Pteromalidae. By studying 26 flowering species, the greatest diversity and density of parasitic wasps were collected from Potentilla reptans, Achillea millefolium, Trifolium repens and Torilis arvensis. In terms of the early flowering plants, the most important results were observed in Euphorbia helioscopia, Senecio vulgaris and Veronica persica. To give an idea of the functional role of these plants, we studied the parasitic wasps of the diapausing larvae (cocoon) of codling moth Cydia pomonella. We recorded three emerged species: Ascogaster quadridentata, Pristomerus vulnerator and the hyperparasite Perilampus fulvicornis. However, none of these species have been observed on the 26 studied plants. Hence, this result may be suggesting that the studied plants do not have a functional role concerning these parasitoids. These studies may be advantageous for biological control programs in order to select flowering plant species attracting parasitic wasps specific to fruit pests.

Reciprocal and coincident patchiness of multiple resources differentially affect benefits of clonal integration in two perennial plants

Summary 1. The modules of plants experience different levels of resources, and clonal plants can integrate resource heterogeneity. However, no studies have tested whether the benefits of clonal integration depend on patterns of heterogeneity in multiple resources, like high levels of above-ground and below-ground resources in the same patches (‘coincident patchiness’) or different patches (‘reciprocal patchiness’). 2. We hypothesized that the benefits of clonal integration can vary depending on whether patchiness is reciprocal or coincident, and that clonal species experience greater benefits from integration when qualitative patterns of resource heterogeneity are more like those likely to occur in their habitats. To test these hypotheses, we grew pairs of connected ramets of Cynodon dactylon and Potentilla reptans under high and low levels of light and of water and soil nutrients, and measured the growth and physiological traits of the plants. 3. Consistent with the hypotheses, connection between ramets in contrasting patches increased final dry mass of Cynodon by 30% compared with connection between ramets within the same type of patch when resource patchiness was coincident, whereas connection decreased mass by 60% when patchiness was reciprocal. Inconsistent with the hypotheses, between-patch connection increased mass of Potentilla by 70% over within-patch connection whether patchiness was reciprocal or coincident; although the species did grow accumulate more mass when patchiness was reciprocal. 4. In Cynodon, treatments had little effect on allocation of mass to roots or specific leaf area; analysis of mass of ramets within pairs suggested that constraints on translocation may have underlain differential effects of reciprocal and coincident patchiness on performance. In Potentilla, treatments affected all measured characteristics, suggesting a higher degree of clonal integration that may have allowed clones to benefit strongly from integration regardless of pattern of resource patchiness. 5. Synthesis. The ability of some plant species to benefit from clonal integration can depend strongly on whether resource heterogeneity is coincident or reciprocal, while other species may benefit equally from integration under both resource patterns. Our results provide an initial indication that the ecological range of some clonal species may be linked to patterns of resource patchiness via traits of clonal integration.

Evaluation of Chemical Composition and In vitro Digestibility of Appennine Pasture Plants Using Yak (Bos grunniens) Rumen Fluid or Faecal Extract as Inoculum Source

Pastures of the Apennines of Central Italy contribute to feed resources of high altitude (above 1,300 m sea level) grazing systems. The objective of this study was to evaluate the effectiveness of faecal extract from the yak (Bos grunnienes) as an alternative microbial inoculum to rumen fluid for estimation of digestibility of several forage species. Forage samples produced at high altitude were tested in this study: four legumes (Lathyrus sativus L., Lotus corniculatus L., Onobrychis viciaefolia L. and Trifolium pratense L.), three forbs (Achillea millefolium L., Potentilla reptans L. and Teucrium flavum L.) and one grass (Brachipodyum pinnatum L.) were incubated with yak rumen fluid or faecal extract. A large variability in chemical composition was observed among the species collected. Rumen liquor and faecal samples were collected from adult healthy yak. The Daisy II incubator was used to evaluate the nutrient digestibility of forages using rumen liquor as control and faecal extract as alternative microbial inoculum sources. Filter bags containing samples of browse species were added to the four digestion vessels along with their respective inoculum and then incubated for 48 h and dry matter (DM), organic matter (OM), crude protein (CP), neutral and detergent fiber (NDF) digestibility was determined. There was a significant relationship between estimates, indicating that faecal liquor has the potential to be used instead of rumen fluid for estimation of in vitro digestibility of plants. It is concluded that the Daisy II incubator results are appropriate for the determination of

Topical anti-inflammatory activity of ointments with 1% of crude water extracts of rhizoma and herb Potentilla reptans L. in croton oil model of mouse ear inflammation

Topical anti-inflammatory activity of ointments with 1% of crude water extracts of rhizoma and herb Potentilla reptans L. in croton oil model of mouse ear inflammation

Physiological integration impacts nutrient use and stoichiometry in three clonal plants under heterogeneous habitats

AbstractPhysiological integration facilitates clonal plants to deal with heterogeneous resources. However, little is known about how nutrient patchiness affects its use and stoichiometry in clonal plants. We conducted an experiment with Cynodon dactylon, Glechoma longituba, and Potentilla reptans to address the effects of physiological integration on nutrient use efficiency and N:P ratios. For C. dactylon, the effects of nutrient patchiness on N use efficiency (NUE), P use efficiency (PUE), and N:P ratio were stronger in daughter ramets than in parent ramets; for G. longituba, nutrient patchiness affected PUE and N:P ratio of parent and daughter ramets, but not NUE; for P. reptans, nutrient patchiness decreased NUE, PUE, and N:P ratio, regardless of parent or daughter ramets. PUE was associated with N:P ratios in three clonal plants and this association of NUE with N:P ratios varied with species. Our findings suggest that physiological integration alters nutrient use efficiency and N:P ratios of clonal plants under patchy nutrients and that these effects are linked to clonal species identity.

Genotype–density interactions in a clonal, rosette-forming plant: cost of increased height growth?

Background and Aims Game theoretical models predict that plants growing in dense stands invest so much biomass in height growth that it trades-off with investment in other organs such as the leaves, leading to decreased plant production. Using the stoloniferous plant Potentilla reptans, we tested the hypothesis that genotypes investing more in the petioles in response to increased density show a greater decrease in total plant mass. We also tested whether a greater increase in mother ramet investment would lead to a greater decrease in investment in vegetative propagation. Methods To uncouple costs and benefits of investments in petioles, ten genotypes that were known to differ in their response to shading signals were grown in monogenotypic stands at two different densities. Key Results Genotypes differed in their increase in petiole investment in response to an increase in density, but not in their decrease in total plant mass or root mass. Total lamina area per plant did not differ significantly between the densities, nor did the mass invested in the laminae per unit of total plant mass. Genotypes differed considerably in the change in vegetation height and petiole investment, but this was not significantly negatively correlated with the change in total plant mass. The genotypes did differ in the change of mass investment in the mother ramet: a greater increase in investment in the mother ramet was correlated to a greater decrease in vegetative propagation. Conclusions While a greater increase in height investment did not lead to a greater decrease in biomass production, it did lead to a decrease in vegetative propagation. This ability to change allocation towards the mother ramets may imply that competition within a stand of stoloniferous plants does not necessarily result in lower total biomass production due to increased height investment.

Photosynthesis of a temperate fallow C<sub>3</sub> herbaceous ecosystem: measurements and model simulations at the leaf and canopy levels

The objectives of the study were to characterize photosynthesis of temperate fallow C3herbaceous species and examine the performance of a simple photosynthesis model (based on the Farquhar's equations) to simulate carbon fluxes at the leaf and canopy levels. The maximum rate of carboxylation at 25°C (V m0) was estimated for sunlit leaves using in situ gas exchange data under saturating irradiance. Throughout the seasons, leaf measurements indicate that values of V m0 were similar for the four major species of the fallow. The rate declined from March (100 µmol m-2 s-1) to July (50 µmol m-2 s-1) and remained almost constant until November. The maximum quantum yield estimated for Potentilla reptans L. (dominant species) was 0.082 mol(CO2) mol-1(photon absorbed), similar to values already published for C3 species. Leaf area index (LAI) increased from winter (less than 0.2 m2 m-2) to spring (up to 4 m2 m-2). Rates of canopy photosynthesis (measured with a canopy chamber) strongly depended on LAI and temperature, in addition to irradiance. They reached a maximum of 25 µmol m-2 s-1 and were intermediate between those published for C4 grassland or cultivated species, and on woody species. At leaf level, simulations gave realistic predictions. At canopy level, the model had the ability to reproduce the effects of environmental and seasonal conditions. However, simulations underestimated the photosynthetic activity of the fallow canopy.

Potentilla reptansis an Alternative Host for Two Strawberry Viruses

Strawberry [Fragaria x ananassa Duchesne = Potentilla x ananassa (Rozier) Mabb] has accumulated a variety of viruses in its relatively short history. Strawberry crinkle virus and Strawberry mild yellow edge virus are transmitted obligately by the aphid Chaetosiphon fragaefolii (Cockerell), which also occasionally infests other species of Potentilla. Several wild strawberry species have been shown previously to be hosts of the viruses. Leaves infected with these strawberry viruses were grafted into plants of UC-5, an indicator strawberry cultivar, and then UC-5 leaves were grafted into Potentilla reptans. Leaves from P. reptans were subsequently grafted back to uninfected UC-5 plants to demonstrate their potential as reservoirs for the virus. UC-5, Fragaria vesca and P. reptans plants were indexed for strawberry viruses by end-point reverse transcriptase PCR subsequent to back grafting.

Carbon gain in the competition for light between genotypes of the clonal herb Potentilla reptans

Summary Different views exist as to what traits will lead to dominance when plants compete for light. One view is that taller plants with better relative positions in the canopy will exclude shorter plants because they intercept almost all light and thus can achieve a higher carbon gain. Alternatively, resource competition models predict that plants that are capable of positive net photosynthesis at the lowest light level will win. In a 5‐year‐old dense competition experiment with 10 genotypes of the clonal plant Potentilla reptans, both these views were tested to see if either of them could explain the dominance of one of the genotypes, or the possible coexistence of several others. Using a combination of measured morphological and physiological traits, a canopy model was constructed to calculate whole‐shoot daily photosynthetic rates of the genotypes in the different layers of the canopy in relation to the invested mass. Results show that the dominant genotype exhibited characteristics of relative shade tolerance: low rates of light‐saturated photosynthesis and respiration. This resulted in a calculated daily carbon gain at the bottom of the canopy, where other genotypes could not achieve that. However, the dominant genotype did not have the highest photosynthetic rates throughout the whole canopy. Some genotypes that persisted in the stand in coexistence with the dominant one achieved greater daily carbon gain at the top of the canopy. Synthesis. The dominant genotype had characteristics similar to those predicted by resource competition models such as the ability to have positive growth at lower light levels. The persistence of several other genotypes, in contrast, may be explained by traits that allowed them to achieve higher carbon gains at the top of the canopy. This suggests that the light gradient formed by the plants themselves creates enough heterogeneity for strategies for dealing with different light requirements to coexist, even within a single species.

Do turloughs occur in Slovenia?

Micheline Shehy Skeffington & Nick. E. Scott: Do turloughs occur in Slovenia? Turloughs are karst basins that fill seasonally with mostly groundwater and drain, usually in summer, to reveal a sedge or grassland community. They are often described as being virtually unique to Ireland. The much larger seasonal poljes of the Slovenian karst are considered different to turloughs. However, a series of small temporary karst lakes in the Slove­nian Pivka valley seem remarkably similar to Irish turloughs. Like turloughs, they fill and empty largely through estavelles connecting to underground water systems, which rise and fall with high seasonal rainfall. The Slovenian sites, however, support less wetland communities than Irish turloughs, prob­ably due to drier summer conditions. The plant communities of both systems occur in zones around the basin, related to flood duration. Releves taken at five Slovenian sites revealed that Petelinjsko jezero, which floods longest each year, is the most similar to turloughs, with, in the lower basin, Eleocharis palustris, potentilla reptans and the unusual form of Ranuculus repens commonly found in Irish turloughs. The difference in climate and terrain means that the Slovenian sites are managed for hay or silage, while the Irish turloughs are under pasture. However, for both, regular flooding precludes much agricul­tural improvement, so that they are now refuges for flora and fauna. A revised definition for turloughs is proposed and a case made for these Slovenian wetland systems to be recognised as turloughs and for the EU Habitats Directive to be amended to include poljes and other similar temporary karst wetland sys­tems as well as turloughs.

Leaf Investment and Light Partitioning among Leaves of Different Genotypes of the Clonal Plant Potentilla reptans in a Dense Stand after 5 Years of Competition

While within-species competition for light is generally found to be asymmetric - larger plants absorbing more than proportional amounts of light - between-species competition tends to be more symmetric. Here, the light capture was analysed in a 5-year-old competition experiment that started with ten genotypes of the clonal plant Potentilla reptans. The following hypotheses were tested: (a) if different genotypes would do better in different layers of the canopy, thereby promoting coexistence, and (b) if leaves and genotypes with higher total mass captured more than proportional amounts of light, possibly explaining the observed dominance of the abundant genotypes. In eight plots, 100 leaves were harvested at various depths in the canopy and their genotype determined to test for differences in leaf biomass allocation, leaf characteristics and the resulting light capture, calculated through a canopy model using the actual vertical light and leaf area profiles. Light capture was related to biomass to determine whether light competition between genotypes was asymmetric. All genotypes could reach the top of the canopy. The genotypes differed in morphology, but did not differ significantly in light capture per unit mass (Phi(mass)) for leaves with the laminae placed at the same light levels. Light capture did increase disproportionately with leaf mass for all genotypes. However, the more abundant genotypes did not capture disproportionately more light relative to their mass than less-abundant genotypes. Vertical niche differentiation in light acquisition does not appear to be a factor that could promote coexistence between these genotypes. Contrary to what is generally assumed, light competition among genetic individuals of the same species was size-symmetric, even if taller individual leaves did capture disproportionately more light. The observed shifts in genotype frequency cannot therefore be explained by asymmetric competition for light.

Effects of inoculation with native arbuscular mycorrhizal fungi on clonal growth of Potentilla reptans and Fragaria moschata (Rosaceae)

Many clonal plants live in symbiosis with ubiquitous arbuscular mycorrhizal (AM) fungi, however, little is known about their interaction with respect to clonal reproduction and resource acquisition. The effects of arbuscular mycorrhiza on the growth and intraclonal integration between ramets of two stoloniferous species were studied experimentally in a nutritionally homogenous soil environment. Two species coexisting at the same field site, Potentilla reptans and Fragaria moschata, were selected as model plants for the study. Pairs of their ramets were grown in neighbouring pots with each ramet rooted separately. Four inoculation treatments were established: (1) both mother and daughter ramets remained non-inoculated, (2) both ramets were inoculated with a mixture of three native AM fungi from the site of plant origin, (3) only mother or (4) daughter ramet was inoculated. The stolons connecting the ramets were either left intact or were disrupted. Despite the consistent increase in phosphorus concentrations in inoculated plants, a negative growth response of both plant species to inoculation with AM fungi was observed and inoculated ramets produced fewer stolons and fewer offspring ramets and had lower total shoot dry weights as compared to non-inoculated ones. A difference in the extent of the negative mycorrhizal growth response was recorded between mother and daughter ramets of P. reptans, with daughter ramets being more susceptible. Due to AM effect on ramet performance, and thereby on the source-sink relationship, inoculation also significantly influenced biomass allocation within clonal fragments. Physiological integration between mother and daughter ramets was observed when their root systems were heterogeneous in terms of AM colonization. These results hence indicate the potential of mycorrhizal fungi to impact clonal growth traits of stoloniferous plant species, with possible consequences for their population dynamics.