Ranunculus Repens Research Articles

The effect of thermal time and soil water on emergence of Ranunculus repens

The effect of temperature and soil available water (AW) on the emergence of Ranunculus repens␣L. was examined in artificial media in growth chambers. Two seed populations, `arable type' and `wild type', were investigated. Moisture levels were 20%, 40%, 60% and 80% AW, and temperatures were 10/5 °C, 15/7 °C, 20/10 °C and 25/15 °C. Time to onset of emergence varied from 11 to 28 days for both seed populations, primarily as a result of mean temperature. Mean thermal time (TT) required for the onset of emergence of both populations was 251 ± 45 TT. Total emergence of the `arable type' R. repens varied from 3% at 10/5 °C and 20% AW to 30% at 25/15 °C and 60% AW. Total emergence of the `wild type' was greater, ranging from 4% at 10/5 °C and 20% AW to 57% at 25/15 °C and 80% AW. Temperature and AW significantly affected total emergence. A logistic response was displayed for the cumulative emergence of both populations. Seedling emergence models based on TT were developed for both populations at each of the four levels of AW.

Species composition of soil seed bank and seed rain of abandoned wet meadows and their relation to aboveground vegetation

Until the late fifties of this century species rich wet meadows were characteristic of the swampy alluvial plains in SchleswigHolstein (north-western Germany). Today many of these meadows undergo successional changes due to abandonment. The vegetation development after abandonment can be characterised as a sequence of different successional stages. After an initial phase(successional stage I) follows a phase of clonal expansion of highly competitive species (successional stage II) and a phase of immigration and establishment (successional stages III and IV). In the course of succession species richness decreases and highly productive vegetation-stands develope. Species contributing to successional changes can either be present in the initial aboveground vegetation, in the soil seed bank or in the seed rain. The species composition of the seed bank and of the seed rain of different successional stages of abandoned wet meadows was investigated. Furthermore the relation between aboveground vegetation and seed bank and between aboveground vegetation and seed rain were determined using a cluster analysis. Seeds of some typical wet meadow ( Lychnis flos-cuculi ) and forage meadow species ( Cardamine pratensis, Cerastium holosteoides, Ranunculus repens, Poa trivialis ) are regulary present in the seed bank of later successional stages, whereas they are absent in the aboveground vegetation there. Thus the aboveground vegetation of permanent plots of the early successional stage I clusters with the seed bank of all permanent plots in the cluster analysis. On the other hand the aboveground vegetation of the permanent plots of the later successional stages II and III constitute cluster. The results of this study support the view, that even if the seed bank of later successional stages contains some species of earlier stages, the possibility to re-establish species rich meadows from species poor fallows is relatively low. This is due to the fact, that seedling-densities of meadow species are decreasing exponentially during succession. Furthermore, rare or endangered plant species are scarcely ever found in the seed bank. The seed rain contains almost exclusively species of the aboveground vegetation present on the permanent plots and the surrounding area. No diaspores of characteristic meadow species were trapped in the seed traps, if these species were absent from the aboveground vegetation or did not produce seeds during the investigation period. Thus, the similarity of the aboveground vegetation of all permanent plots with the seed rain is very high; cluster analysis indicates that the aboveground vegetation of each permanent plot clusters with the seed rain of the same plot. The great similarity of the aboveground vegetation of all permanent plots with the seed rain is caused by the small dispersal distances of most of the occurring species. Both diaspores of herbaceous ( Urtica dioica, Galeopsis tetrahit agg.) and woody ( Alnus glutinosa, Betula pubescens, Salix alba ) invasive species were trapped in seed traps in some cases. It can be concluded that the seed rain of abandoned wet meadows has an essential impact on progressive secondary succession (transition between successional stage II and III and between successional stage III and IV), while it has only a subordinate role in restoring species rich wet meadows from abandoned sites, that is in regressive succession.

Temperature Adaptation and Acclimation Potential of Leaf Dark Respiration in Two Species of Ranunculus from Warm and Cold Habitats

Rates of evolutionary thermal adaptation (i.e. hereditary adjustment to the thermal environment) of plant dark respiration will likely be too slow to keep up with predicted rapid climate changes. However, thermal acclimation to novel temperatures (i.e. shorter-term phenotypic adjustment to changes in the thermal environment) may be sufficient for plants to adjust to rapidly changing temperatures. We measured nighttime leaf dark respiration in the arctic/alpine species Ranunculus glacialis, and in the temperate lowland Ranunculus repens, on plants grown under either cold (10°C/8°C day/night) or warm (22°C/18°C) conditions. Adaptation to their respective native thermal environments was apparent in this pair of species as indicated by similar respiration rates measured at 8°C in R. glacialis grown at cold temperatures and those measured at 18°C in R. repens grown at warm temperatures. Phenotypic thermal acclimation to warmer temperatures was apparent in R. glacialis as indicated by similar rates measured at 8°C in cold-grown and at 18°C in warm-grown plants. Whether this holds true for root systems awaits testing. Our results reemphasize the need to include acclimatory adjustments of plant metabolism in computer models designed to predict the response of vegetation to global change.

Temperature Adaptation and Acclimation Potential of Leaf Dark Respiration in Two Species of Ranunculus from Warm and Cold Habitats

Rates of evolutionary thermal adaptation (i.e. hereditary adjustment to the thermal environment) of plant dark respiration will likely be too slow to keep up with predicted rapid climate changes. However, thermal acclimation to novel temperatures (i.e. shorter-term phenotypic adjustment to changes in the thermal environment) may be sufficient for plants to adjust to rapidly changing temperatures. We measured nighttime leaf dark respiration in the arctic/alpine species Ranunculus glacialis, and in the temperate lowland Ranunculus repens, on plants grown under either cold (100C/80C day/night) or warm (220C/180C) conditions. Adaptation to their respective native thermal environments was apparent in this pair of species as indicated by similar respiration rates measured at 80C in R. glacialis grown at cold temperatures and those measured at 180C in R. repens grown at warm temperatures. Phenotypic thermal acclimation to warmer temperatures was apparent in R. glacialis as indicated by similar rates measured at 80C in cold-grown and at 180C in warm-grown plants. Whether this holds true for root systems awaits testing. Our results reemphasize the need to include acclimatory adjustments of plant metabolism in computer models designed to predict the response of vegetation to global change.

Preliminary studies of the impact of excreted N on cycling and uptake of N in pasture systems using natural abundance stable isotopic discrimination

The possibility of using natural abundance techniques to determine N transformations and flows after deposition of cattle dung has been examined. These preliminary results showed that δ15N in dung was greater than in plants growing in association with particular pats. This, and other observational information, indicated that dung pats of different ages were being examined. There were significant variations in plant δ15N signatures within and between species grown in association and away from the dung. It was probable that variation in plant δ15N was brought about by changes in soil mineral N pools after transfer of N derived from the dung. This resulted in different δ15N signatures in Trifolium repens (because of changes in N utilization from soil or atmospheric pools), in Lolium perenne (because of changes in δ15N in soil mineral N), but not in Ranunculus repens (because the majority of active roots were outside the range of immediate influence of the deposited dung). The differences in δ15N allowed the development of hypotheses for changes in soil N pools and the acquisition of N by plants from soil, dung or atmospheric sources.

Leaf appearance and senescence patterns of some pasture species

AbstractFive pasture species, very different in their morphological organization (four dicotyledons: Plantago lanceolata, Sanguisorba minor, Ranunculus repens, Taraxacum officinalis and one grass: Dactylis glomerata), were grown as spaced plants in pots, thus excluding competition for light, to study the proportion of senescent leaves. In May, after a 6 month period, the proportion of partially or totally senescent leaves varied from 20% to 80%. Four plant characteristics were important: leaf appearance and senescence rates, leaf lifespan and date and type of flowering. Plantago lanceolata had the longest lived foliage and the smallest proportion of senescent leaves. In contrast, Taraxacum officinalis had the most rapid leaf turnover and Dactylis glomerata had the slowest rate of leaf appearance. Sanguisorba minor and Ranunculus repens were almost identical, with intermediate leaf characteristics in all respects. These results illustrate the fact that the four characteristics studied, and not simply the species' phenology, must be taken into account in order to compare growth between species. The likelihood of these characteristics remaining the same when species are in dense sward is considered.

Trends in the botanical composition of set-aside fields in North-east Scotland uncultivated for five years

Summary Species composition was monitored in 13 set-aside fields from 1989 to 1993 and in six others from 1989 to 1991. Grasses contributed more cover than dicotyledonous species throughout, but weedy species, e.g. Agrostis gigantea and Poa annua, were steadily replaced by grasses of permanent grassland, e.g. Agrostis capillaris, Dactylis glomerata and Holcus lanatus. Ranunculus repens (creeping buttercup) and Trifolium repens (white clover) became the main dicotyledonous species, and weeds characteristic of arable land had negligible cover after the first year of set-aside. As a result species richness declined, herbs of semi-natural grasslands being slow to colonize; many entrant species were recorded only in edge quadrats which extended 5 m into the fields from the headland. Noxious weeds (docks, ragwort and thistles) remained at low cover levels.

Field evidence of plastic growth responses to habitat heterogeneity in the clonal herb Ranunculus repens

AbstractStolon internode lengths were measured on plants of the clonal herb Ranunculus repens growing in a hay meadow which was subject to disturbance by mole (Talpa europaea) activity. Within the site three habitat types were recognized: closed grassland, the open ground of fresh molehills and the grass‐molehill boundary. The lengths of stolon internodes of R. repens differed significantly in each of the three habitats. The shortest internodes occurred on stolons on the open molchills. The longest occurred in the closed grassland habitat. The type of habitat in which parent ramets were rooted did not significantly influence the length of internodes on their daughter stolons. The length of a stolon internode was determined by its immediate surrounding habitat type. Consecutive internode lengths on a given stolon showed considerable plasticity, shortening significantly as stolons spread onto molehills from surrounding habitats, and increasing significantly as stolons advanced from a molehill into the surrounding closed grassland habitat. These results are consistent with the proposition that under favorable conditions (on the molehills, where resources are expected to be more abundant, and competition absent) internode lengths shorten and the plant forages intensively, whereas under conditions of low resource availability (in the closed grassland, where competition occurs) internode lengths increase, allowing R. repens to forage extensively. Such morphological plasticity may promote more efficient exploitation of resource‐rich sites and more rapid vacation of resource‐poor sites.

Seedling Recruitment and the Maintenance of Clonal Diversity in Plant Populations--A Computer Simulation of Ranunculus Repens

1 A computer simulation model is developed to examine the effects of varying levels of seedling recruitment, mortality and rates of clonal growth on genet diversity in populations of the clonal perennial herb, Ranunculus repens. 2 It is shown, following an initial colonization event, that there is a rapid loss of genets from populations in which there is no further seedling recruitment, and that such populations become dominated by a few large clones. Nevertheless coexistence of a high density of genets is possible in the short term in the nonequilibrium situation occurring immediately after a large scale disturbance. 3 The input of only a few seedlings each year into a population of ramets accelerates the loss of founder genets but acts as a powerful mechanism for maintaining genet diversity in populations. Varying the level of density-dependent mortality and the rate of clonal growth also influences genet diversity. 4 Taking the results of all the simulations together it is demonstrated that it is the ratio of seedling to ramet recruits that is crucial in determining the genetic architecture of clonal plant populations both in terms of the number and size hierarchy of genets. Significant variation in the relationship between population structure and the ratio of seedling to ramet recruits was related primarily to low initial population densities and subsequent low seedling inputs. 5 The low ratio of seedling to ramet recruits observed in many plant populations where seedling recruitment occurs within established populations is shown to be sufficient to maintain quite high genet densities relative to the total number of ramets, unless there is strong competition between genets. 6 Inequality in the genet size of clonal plants increases with time and also with a decrease in the ratio of seedling to ramet recruits, except at very low values where there is again a decrease in inequality. The development of genet size hierarchies in clonal plants is compared with that of aclonal plants.

Weeds as hosts of Mycocentrospora acerina

SummaryWeeds were collected from carrot fields and some other sites at 27 localities in seven counties in Norway during August and September of 1986 and 1987. Leaf and petiole lesions were microscopically examined for Mycocentrospora acerina. Viola arvensis and Viola tricolor were commonly observed with the pathogen. The fungus was also registered on Fumaria officinalis, Galium aparine, Matricaria inodora, Matricaria matricarioides, Ranunculus repens, Senecio vulgaris and Stachys palustris. In inoculation experiments in the greenhouse, M. acerina infected carrot leaves and 13 of 16 species of weeds. The symptoms on the various susceptible plants showed some variation, but were essentially of the same pattern. The investigation indicates that weeds are common hosts of M. acerina. A list of 23 host weed species is given.

Macrofossil finds of henbane ( Hyoscyamus niger) in the old settlement layers in southern Finland

The macrofossil seed finds of henbane ( Hyoscyamus niger L.) from five settlement sites in southern Finland were analyzed. The sites were dated archaeologically from the Viking Age to the 19th century. The number of studied soils samples was 492. The seeds of henbane were quite common in the late medieval settlement layers of Turku, Kaarina, the bishop's castle of Kuusisto, and also in the layers of the 17th century of the fortress in Lappeenranta. Few seeds were found from the 18th century layers of Naantali, and one charred seed from the level of an ancient field in Rapola, Sääksmäki dated to the Viking Age. The associate species from all the sites were more or less common settlement weeds, such as Chenopodium album, C. glaucum, C. rubrum, C. suecicum, Ranunculus repens, Taraxacum officinale, Urtica dioica and U. urens. Most probably, the henbane was carried by man to the studied sites as a medicinal plant. The studied site of Turku was the location of a poorhouse and a hospital in the Middle Ages. The inhabitants of the castle of Kuusisto were in direct contact with the monks and nuns of the convent of Naantali where medicinal herbs were cultivated in the Middle Ages. The henbane was carried to Lappeenranta probably by soldiers or shopkeepers. The oldest find of henbane came from Rapola, Sääksmäki and dated to the Viking Age. It was found from the layer of an ancient field near an ancient castle hill. According to the present macrofossil finds, the henbane was carried to southern Finland at the same time as to Sweden.

THE BIOLOGY OF CANADIAN WEEDS.: 95. Ranunculus repens

Ranunculus repens L. (creeping buttercup) is a common weed in the Maritimes, Ontario and Quebec, as well as British Columbia. A review of the literature on the biology of the species is presented. Ranunculus repens can develop large spreading clones as it produces ramets on stolons, and readily regenerates from root fragments. It is therefore particularly resistant to cultivation as a weed control strategy. It is, in addition, partially, or fully resistant to many herbicides, and its seeds show dormancy and sustained viability in the seed bank. Several investigations have been carried out on the population dynamics of this species, and its responses to light and nutrient treatments have been described.Key words: Weed biology, Ranunculus repens, creeping buttercup

Management of Roadside Vegetation: The Long-Term Effects of Cutting

SUMMARY (1) An experimental comparison of the effects of eleven cutting treatments on roadside vegetation was made at two sites in Cambridgeshire over a period of 18 years. The treatments were combinations of cutting date, cutting frequency (0, 1, 2, or 5 times per annum) cutting machine (haymower, flail mower or rotary mower) and leaving or removing cuttings. (2) Vascular plant species-richness of the vegetation was unaffected by altering the date of a single cut from June to July or by cutting with different types of machine. It was lowest in the uncut plots and highest in plots cut twice per annum. (3) Increased cutting frequency significantly decreased the frequency of ten mainly coarse growing species, including Elymus repens, Arrhenatherum elatius and Anthriscus sylvestris. Eleven finer species (mostly grasses) increased in frequency and two others (Ranunculus repens and Plantago lanceolata) reached a maximum at two cuts per annum. (4) Removing cuttings led to an increase in plant species-richness, mainly due to an increase in herbs. Removing cuttings led to a decrease in extractable potassium in the soil but most other soil nutrients, including total and available nitrogen, were unaffected. It is suggested that the increase in species-richness was not due to reduced levels of soil nutrients, but was probably associated with the disturbance and scarification which accompanied the removal of cuttings by hand raking, and with the alleviation of the smothering effect caused by leaving cut vegetation on the verges. (5) The effects of the treatments on species-richness and the frequencies of individual species were very similar at both sites.

Population Dynamics and Local Specialization in a Clonal Perennial (Ranunculus Repens). III. Responses to Light and Nutrient Supply

Population Dynamics and Local Specialization in a Clonal Perennial (Ranunculus Repens). III. Responses to Light and Nutrient Supply

Effects of glyphosate on Fusarium spp.: its influence on root colonization of weeds, propagule density in the soil, and crop emergence

Glyphosate is a broad spectrum herbicide that can lead to root rot like damage on crops. This study was undertaken to investigate the effect of glyphosate on the root-colonizing Fusarium spp. The research was conducted at two sites. Site one was densely covered with perennial weeds, and site two with annuals. At site one, spraying the weed cover with glyphosate increased (p < 0.05) the level of colonization by Fusarium spp. in Ranunculus repens and Holcus lanatus, but not in Stellaria media and Plantago lanceolata. At site two, glyphosate enhanced colonization in Spergula arvensis, Stellaria media, Echinochloa crusgalli, and Chenopodium album, but not in Capsella bursa-pastoris and Polygonum persicaria. At both sites, the number of colony-forming units of Fusarium spp. per gram of dried soil was increased by the application of glyphosate. Nevertheless, crops subsequently sown in the field containing the annual weeds were not detrimentally affected by glyphosate treatment of these weeds.

Alcohol dehydrogenase activity in the roots of marsh plants in naturally waterlogged soils

The aim of this work was to discover whether oxygen tensions in the roots of marsh plants in flooded soils are high enough to allow fully acrobic metabolism. Activity of alcohol dehydrogenase (ADH), a protein synthesised in anoxic plants, was measured in roots of marsh plants growing in habitats where the availability of oxygen to the roots would be expected to differ. Roots of Carex riparia in standing water had ADH activities about 2.5 times higher than those of phosphofructokinase, and comparable to ADH activities of Poa trivialis, Urtica dioica and Ranunculus repens roots in dry soil. Removal of the oxygen supply via aerenchyma to Carex roots caused a 30-fold increase in ADH activity relative to that of phosphofructokinase. There was no change in ADH activity with depth in Carex roots in waterlogged soil, but in Filipendula ulmaria roots activity was 14 times higher below 10 cm depth than near the surface. Urtica roots in waterlogged soil had alcohol dehydrogenase activities 26 times higher than roots in dry soil, but for Poa and Ranunculus roots this figure was only 1.7 and 4.2, respectively. These results indicate that the oxygen tensions in the roots of marsh plants in waterlogged soil differ considerably among species. Ethanol was the major product of fermentation in roots of all species studied. There was no correlation between ADH activity and the rate of ethanol production under anoxia of Urtica roots. The physiological significance of high ADH activities in roots is thus unclear.

Seed survival and seasonal emergence in some species of Geranium, Ranunculus and Rumex

SUMMARYSeeds of 14 species were collected, usually in each of 2 or 3 yr, and mixed with the top 7.5 cm of sterilised soil confined in cylinders sunk in the ground outdoors and cultivated three times yearly. Seedling emergence was recorded for at least 3 and usually 5 yr. Most seedlings of Ranunculus bulbosus and Rumex acetosa appeared during the autumn of sowing, while the main emergence of Geranium pratense. Ranunculus acris, Rumex conglomeratus and R. maritimus was in the following spring. Emergence of G. pyrenaicum and G. robertianum took place throughout much of the year after sowing. Seeds of all these species were relatively short‐lived in cultivated soil, and few seedlings appeared after the second year.Seed survival was greater in G. dissectum. G. molle, Rumex acetosella. Ranunculus sceleratus and especially R. repens, of which emergence in the fifth year after sowing amounted to 4% of the seeds sown. Emergence from the persistent seed bank was mainly from May to September for G. dissectum and G. molle and during autumn for Ranunculus flammula and R. sceleratus, while seedlings of Ranunculus repens and Rumex acetosella appeared sporadically over most of the year.

PHENOTYPIC RESPONSES OF RANUNCULUS REPENS POPULATIONS IN GRASSLANDS SUBJECTED TO DIFFERENT MOWING REGIMES

SUMMARY Populations of Ranunculus repens were studied in grasslands that had been subjected to different hay-making regimes without the application of fertilizers. Cutting for hay occurred either in July, or in July and September, or in September only over a period of nine years that followed a prolonged period of hay-pasture. For comparison, spring and autumn seedlings derived from field populations, also subjected to the different hay-making regimes, were grown under standard conditions in an experimental garden. The differences observed in the field were not retained by the experimental populations with the exception of the seed weight in the spring seedling population. In contrast, differences found in the experimental populations between spring and autumn seedling populations indicated the importance of the time of emergence of seedling cohorts. Populations cut in July seemed to maintain themselves by sexual reproduction. Seedling emergence and survival was higher with the July than the September hay-making regime. The population cut in September maintained itself mainly by vegetative multiplication, since daughter-plants from stolons are independent from the end of August.

The Integration of Neighbourhood Effects by Clonal Genets in Solidago Canadensis

SUMMARY (1) When clones of Solidago canadensis were grown experimentally with pure stands of different species, the neighbouring species had different effects on ramet shoot-growth, flower-head production, and clonal growth. In general, S. canadensis shoot growth and flower production were greatest in the neighbourhood of Poa pratense, and lowest among Aster pilosus, whereas clonal growth was greatest among ramets growing in the A. pilosus neighbourhood and lowest in the Solidago canadensis neighbourhood. (2) When clones of S. canadensis were grown experimentally with each interconnected ramet among a different neighbour species, the effects of the different neighbours were evened out. All ramets responded more or less equitably in their shoot growth, reproduction, and clonal growth, regardless of the identity of their neighbours. These results suggest that clones integrate local neighbourhood variation and that the response of a given ramet to interference from a neighbour species is partly dependent upon the experiences of its interconnected sibling ramets. (3) There are several costs and benefits associated with maintaining physiological interdependency among ramets. Interdependent ramets may support the growth of ramets experiencing intense interference or resource limitation and may benefit from the ability to regulate internally the position and density of shoots within the clone and to overcome local variation in their environment. However, the maintenance of a network of long interconnecting rhizomes may be energetically expensive and may allow certain agents of mortality such as pathogens to spread rapidly among ramets. (4) The growth form of a clone may also influence the relationships between clonal plants and neighbours. Within-clonal Solidago canadensis ramets form pure stands, 1-several metres in diameter, that prevent the invasion of neighbours, distribute the effects of surrounding neighbour species, are buffered against neighbour interference, and expand uniformly in several directions regardless of the identity of neighbours. This is in contrast to patterns in other clonal species, e.g. Trifolium repens and Ranunculus repens in which very long rhizomes or stolons are produced and ramet interconnections are rapidly lost. These species are characterized by extensive lateral mobility and sampling of the environment, the avoidance of interference, and the differential growth of different independent portions of the genet in different parts of the habitat mosaic.

Pichia scaptomyzae sp. nov., isolated from Scaptomyza multispinosa Malloch (Diptera) in southern Chile

A novel representative of the yeast genus Pichia which has been isolated from the intestinal tract of the fly Scaptomyza multispinosa Malloch, (species of Chilian diptera frequenting meadows where Ranunculus repens L. are abundant), is described and illustrated. The strain differs from all accepted Pichia species (1–11) to warrant its establishment as a new species: Pichia scaptomyzae sp. nov.