Geranium Dissectum Research Articles

Interspecies diversity in morphological responses to water stress: Study on a panel of weed and crop species

Climate change modifies the dynamics and the quantity of plant water supply, and plant morphological response to environmental factors plays a key role in crop-weed interactions. This study investigated the interspecies diversity related to the morphological responses of annual herbaceous species to water stress. Key morphological traits were measured at two growth stages on five weed and two crop (soft wheat, rapeseed) species grown on a gradient of water availability in a greenhouse experiment. For each trait, response curves to water stress were defined, and their parameters were used to quantify interspecies diversity. Generic morphological response patterns were identified across all species and plant stages. Water stress reduced leaf area per unit leaf biomass (SLA, lowering water demand) and increased the ratio of plant height to aboveground biomass for all species (HBR, keeping access to light). In most situations, the ratio of root biomass over total biomass (RBR) increased (improving water uptake). Variability in parameter values of morphological traits was primarily explained by the species, followed by growth stage. Geranium dissectum L. and Abutilon theophrasti Medik. were the most responsive species to water stress, especially at the flowering stage, with strong RBR and HBR increase and slight SLA decrease. Species differences were not related to clade (monocotyledonous/dicotyledonous) nor status (weed/crop), despite a near-significant clade effect on allocation of aboveground biomass, with grass species allocating more biomass to stems (vs leaves), while no general tendency was observed in broadleaved species. These findings provide new insights on comparative ecology of weed and crop species response to water limitation, and more research is expected to cover a wider range of weed and crop species.

Three years of warming and rainfall reduction alter leaf physiology but not relative abundance of an annual species in a Mediterranean savanna

Increasing air temperatures and decreasing rainfall can alter Mediterranean ecosystems, where summer heat and drought already limit plant regeneration. Manipulative field studies can help to understand and anticipate community responses to climate changes. In a Mediterranean oak wooded pasture, we have investigated the effects of warming (W, via open-top chambers increasing 1.4 °C mean air temperature), reduced rainfall (D, via gutters removing 33% of rainfall) and the combination of both factors (WD) on the winter-annual Geranium dissectum L. We measured reproductive phenology and output, leaf physiology during the reproductive phase, and plant relative abundance. Warming had a positive effect on plant height and little effects on leaf physiology. Rainfall reduction enhanced leaf water use efficiency. However, the most noticeable effects occurred in WD plants, which exhibited lower leaf predawn water potential and earlier flowering phenology in the first year of treatment, and a higher ratio of leaf dark respiration (R) to net CO2 assimilation (Pn) at comparable temperatures in the third year, compared to control plants. Leaf R at ambient temperature was similar across climatic treatments. The relative abundance of G. dissectum decreased by 23% over three years, but similarly across treatments. A short life cycle helps G. dissectum to escape severe late-spring heat and drought stress. Moreover, stomata closure and thermal acclimation of R can attenuate plant stress impact on reproduction. Adaptability of the short-lived annual G. dissectum could mitigate climate change impact on community composition over short periods (e.g. three years); however, a reduction in net carbon gain could eventually affect its reproductive success and persistence in the community.

New and Noteworthy Records of Vascular Plants for Kansas

Recent fieldwork in eastern Kansas resulted in the discovery to two species of vascular plants previously unreported in the state (Aphanes australis, Mazus miquelii) and new collections of six species previously documented by historical collections or few recent collections (Cerastium dubium, Crepis capillaris, Geranium dissectum, Ranunculus parviflorus, Torilis nodosa, Trifolium resupinatum). All species reported here are considered non-native in Kansas.

Weed suppression in cover crop mixtures under contrasted levels of resource availability

Cover crop (CC) mixtures appear as a promising agroecological tool for weed management. Although CC supress weed growth by competing for resources, their suppressive effect under contrasting levels of soil resource availability remains poorly documented. A two field:year experiment was conducted to investigate the weed suppressive effect of four CC mixtures. They were composed of 2 or 8 species including or not legume species and compared to a bare soil control. The experiment included two levels of irrigation and nitrogen fertilisation at CC sowing. The objectives were to assess (i) weed and CC aboveground biomass response to CC mixtures and resource availability, (ii) the weed suppressive effect of CC mixtures across a gradient of CC biomass and (iii) weed community response to CC mixtures and resource availability. CC and weed biomass were mainly influenced by interactions between CC mixtures and fertilisation and between CC mixtures and irrigation, with contrasted effects between field:years. Nitrogen fertilisation increased biomass of non-legume based CC mixtures but this only resulted into a further reduction of weed biomass of little biological relevance. Legume-based CC mixtures suppressed weeds to a greater extent without nitrogen fertilisation in year 2 but not in year 1, possibly due to contrasted initial soil nitrogen availability (lower in year 2). Weed biomass generally benefited more from irrigation than CC mixtures. Among the 33 weed species recorded, weed communities in each plot were dominated by wheat volunteers, Geranium dissectum, Veronica persica and Echinochloa crus-galli, whose biomass varied depending on the interaction between year, CC mixture and resource availability. Our results revealed that competitive outcomes between CC mixtures and weed species were driven by a complex interaction between resource availability and species traits. Further experiments focusing on plant traits should improve our understanding of weed:CC competitive outcomes under various levels of resource availability.

Climate-driven variation in biotic interactions provides a narrow and variable window of opportunity for an insect herbivore at its ecological margin.

Climate-driven geographic range shifts have been associated with transitions between dietary specialism and generalism at range margins. The mechanisms underpinning these often transient niche breadth modifications are poorly known, but utilization of novel resources likely depends on phenological synchrony between the consumer and resource. We use a climate-driven range and host shift by the butterfly Aricia agestis to test how climate-driven changes in host phenology and condition affect phenological synchrony, and consider implications for host use. Our data suggest that the perennial plant that was the primary host before range expansion is a more reliable resource than the annual Geraniaceae upon which the butterfly has become specialized in newly colonized parts of its range. In particular, climate-driven phenological variation in the novel host Geranium dissectum generates a narrow and variable 'window of opportunity' for larval productivity in summer. Therefore, although climatic change may allow species to shift hosts and colonise novel environments, specialization on phenologically limited hosts may not persist at ecological margins as climate change continues. We highlight the potential role for phenological (a)synchrony in determining lability of consumer-resource associations at range margins and the importance of considering causes of synchrony in biotic interactions when predicting range shifts. This article is part of the theme issue 'Species' ranges in the face of changing environments (Part II)'.

Investigating the effects of temperature on seed germination of cutleaf geranium (Geranium dissectum L.) and determination of its cardinal temperatures

Cutleaf geranium is a weed infesting crop fields in various parts of the world. The present study was conducted to determine the cardinal temperatures of germination for its seeds to have a better understanding about temperature needs of this species. Since the seeds were dormant after being harvested, they underwent different dormancy breaking methods. Then, cardinal temperatures were estimated. Among dormancy breaking methods including constant and alternating temperatures, gibberellic acid, H2SO4 and gibberellic acid+ H2SO4 treatments, pre-chilling and after-ripening, after-ripening was the most successful one. Dent and segmented models were the most suitable models for determination of cardinal temperatures. Base, optimum, and ceiling temperatures for dent model were estimated 0.02, 18.97 to 25.32, and 27.00 °C, respectively. These values for segmented model were 0.01, 24.3 and 27.08 °C. The seeds showed high germination uniformity at 15 and 20 °C, but they entered into a state of thermo-dormancy as temperature reached about 27 °C. According to the temperature conditions of the studied region, early sowing of canola will result in the weed being faced with higher than ceiling temperatures. Thus, generalizing, the proper sowing date may be regarded as a feasible management practice in controlling this weed in any given area. This was the first report on estimation of cardinal temperatures in cutleaf geranium.

First report of Barley Yellow Dwarf Viruses (BYDVs) on dicotyledonous weed hosts in Turkey

Yellow dwarf viruses (YDVs) are economically destructive viral diseases of cereal crops, which cause the reduction of harvested yield and quality of grains. Up to now the identification of such viruses was limited to monocotyledonous Poaceae weed hosts, and was not investigated in dicotyledons. In this study, using DAS-ELISA and RT-PCR methods, 6 dicotyledonous weed species, collected from Trakya, Turkey, were examined for the presence of the YDVs pathogens BYDV-PAV, BYDV-MAV, BYDV-RMV, BYDV-SGV and CYDV-RPV. The screening tests revealed certain samples of Geranium dissectum L. and Juncus compressus Jacq. were infected with BYDV-PAV, while other samples of the same species were positive for BYDV-MAV. Additionally, RT-PCR tests of both weed species revealed cases of mixed infection by BYDV-PAV and BYDV-MAV. Transmission experiments using the aphid species Rhopalosiphum padi L. showed that BYDV-PAV was transmitted persistently from Geranium dissectum to barley cv. Barbaros seedlings. To our knowledge, this is the first report of Geranium dissectum and Juncus compressus as possible plant hosts of BYDV-PAV and BYDV-MAV in Turkey.

Floristički sastav hrastovih šuma i šibljaka grabića prve tri godine nakon požara na planini Vidlič

After a catastrophic wildfire on Vidlič Mountain in 2007, which among other things burned oak forests and hornbeam scrubs, their floristic composition was monitored for three years. Phytosociological surveys were carried out in the field using the Braun-Blanquet method, and the results are presented in the form of a synthetic phytosociological table. It was observed that in the stands in which the vegetation was only partially damaged, a shorter recovery time was required to return to the previous state - as it was before the wildfire. The initial stages of vegetation recovery at sites where complete destruction of vegetation occurred were characterized by a strong presence of annual therophytes: Orlaya grandiflora, Sideritis montana, Geranium dissectum, Althaea hirstuta. The first year after the wildfire was characterized by the dominance of annual species of Bupleurum praealtum, Crepis setosa and Centaurea calcitrap, which were not recorded in the monitored stands in the second and third year after the wildfire. In the second and third year after the wildfire, perennial plants and various grass species assumed dominance. It is necessary to conduct further systematic and continuous monitoring of the floristic composition and structure of the oak forests that completely burned in the wildfire, as well as an analysis of the profitability of the restitution of oak forests damaged by forest fires in Serbia.

Požarište bukove šume na lokalitetu Visoka stena prve godine posle požara na planini Vidlič

In the summer of 2007. the wildfire occurred on the Vidlic Mountain, in which burned vegetation of beech forests. Phytocenological study of vegetation of beech forest at locality Visoka stena the first year after fire was carried out in accordance with the method of Braun-Blanquet. The results of field research are presented in the form of phytocoenological table. It was noticed that the species with the highest degree of presence are: Rubus idaeus, Sorbus aria, Acer campestre, Spiraea chamaedryfolia, Doronicum columnae, Poa compressa, Galium mollugo, Epilobium angustifolium, Lamium maculatum. The first post-fire year was characterized by annual species domination (Geranium dissectum, Geranium robertianum). It was noticed a significant presence of busy grass (Poa nemoralis, Poa angustifolia, Agrostis capillaris, Brachypodium pinnatum). Recovering of vegetation of beech forest on the locality Visoka stena depends on the degree to which the number of beech trees has been destroyed, or whether it was burnd partially or completely.

Trophic Relationships between the Parasitic Plant Species Phelipanche ramosa (L.) and Different Hosts Depending on Host Phenological Stage and Host Growth Rate.

Phelipanche ramosa (L.) Pomel (branched broomrape) is a holoparasitic plant that reproduces on crops and also on weeds, which contributes to increase the parasite seed bank in fields. This parasite extracts all its nutrients at the host’s expense so that host–parasite trophic relationships are crucial to determine host and parasite growth. This study quantified the intensity with which P. ramosa draws assimilates from its host and analyzed whether it varied with host species, host phenological stage and host growth rate. A greenhouse experiment was conducted on three host species: the crop species Brassica napus (L.) (oilseed rape) and two weed species, Capsella bursa-pastoris (L.) Medik. and Geranium dissectum (L.). Plants were grown with or without P. ramosa and under three light levels to modulate host growth rate. The proportion of host biomass loss due to parasitism by P. ramosa differed between host species (at host fructification, biomass loss ranged from 34 to 84%). B. napus and C. bursa-pastoris displayed a similar response to P. ramosa, probably because they belong to the same botanical family. The sensitivity to P. ramosa in each host species could be related to the precocity of P. ramosa development on them. Host compartments could be ranked as a function of their sensitivity to parasitism, with the reproductive compartment being the most severely affected, followed by stems and roots. The proportion of biomass allocated to leaves was not reduced by parasitism. The proportion of pathosystem biomass allocated to the parasite depended on host species. It generally increased with host stage progression but was constant across light induced-host growth rate, showing that P. ramosa adapts its growth to host biomass production. The rank order of host species in terms of sink strength differed from that in terms of host sensitivity. Finally, for B. napus, the biomass of individual parasite shoots decreased with increasing their number per host plant, regardless of host growth rate. Results will be incorporated into a mechanistic model in order to analyze the effect of parasitic plant species on weed community assembly and to design new cropping systems for controlling P. ramosa.

Weed seed distribution in the soil profile in extensive and intensive vineyards

Determination of weed seed bank is of great importance for the study of weed population dynamics and planned weed control. In agroecosystems knowledge of weed seed bank in a particular area provides better choice of cultural practices, as well as more rational herbicide use. Extensive growth of vine grape implies application of all cultural practices without herbicide use. Soil samples for determination of weed seed bank were taken at the beginning and at the end of vegetation period. Soil samples were taken from each plot in ten replications. The samples were taken from depths of 0-10 cm, 10-20 cm and 20-30 cm, separately. The aim of the study was to establish the composition of weed seed bank in extensive and intensive vineyards. In extensive vineyard 24 weed species were determined, and in intensive 20 ones and these were: Portulaca oleracea L., Amaranthus retroflexus L., Stellaria media (L.) Vill., Chenopodium album L., Euphorbia helioscopia L., Galium verum L., Polygonum persicaria L., Datura stramonium L., Setaria glauca (L.) Beauv., Solanum nigrum L., Stachys annua L., Geranium dissectum L., Veronica arvensis L., Euphorbia ciparissias L., Convolvulus arvensis L., Sinapis arvensis L., Viola tricolor L., Capsella bursa-pastoris L., Lamium purpureum L., Polygonum aviculare L., Papaver rhoeas L., Ambrosia artemissifolia L., Agropyrum repens (L.) Beauv., and Sorghum halepense L. In addition to the great variety of weed species, whose seeds were determined from the studied samples, only the following few species proved to be dominant with a greater number of seeds: Amaranthus retroflexus L., Portulaca oleracea L., Capsella bursa-pastoris L., Chenopodium album L., Stellaria media (L.) Vill., Solanum nigrum L., and Lamium purpureum L.

Survey of Twospotted Spider Mite (Acari:Tetranychidae) Host Plants in the Mississippi Delta

Abstract A survey of twospotted spider mite, Tetranychus urticae Koch, hosts was conducted during the spring months of 2007, 2008, and 2009 in Mississippi. Uncultivated field borders that supported a diverse flora of herbaceous plants and adjacent in-field weeds were sampled from late-March through May for the presence of twospotted spider mite. Twospotted spider mite preference for each plant species was determined and ranked in a 0 - 3 scale. Henbit, Lamium amplexicaule L., was the most consistent and preferred host of twospotted spider mite in Mississippi. Carolina geranium, Geranium carolinianum L., cutleaf geranium, Geranium dissectum L., vetch, Vicia spp., volunteer soybean, Glycine max L., purple deadnettle, Lamium purpureum L., and spiny sowthistle, Sonchus asper (L.) Hill, were other frequently infested dicotyledonous species. Of the monocotyledonous species sampled, only rescuegrass, Bromus catharticus Vahl, john-songrass, Sorghum halepense (L.) Pers., and volunteer corn, Zea mays L., appeared t...

The stubble-field plant communities in South-Eastern Poland. P. III. Plant communities of mountain agricultural utility complexes

In the Part I and II the stubble-field plant communities of lowlands agricultural utility complexes in South-Eastern Poland were introduced. The Part III contains a description of such communities occurring in mountain complexes. In the years 1972-1975, since August till September, 95 phytosociological records were taken on the area elevated from 300 to 650 m over the sea level, embracing the Carpathian Foreland and the Low Carpathian region. The research was conducted upon the typical, acid and leached brown soils, as well as on clay, dusty clay and silt alluvial soils belonging to three mountain complexes: wheat, cereal and oat-potatoes. The following communities were specified: I. <i>Setaria glauca</i> community, divided into two variants: 1) typical; 2) with <i>Aphanes arvensis</i>; II. <i>Veronica persica</i> community, divided into four variants: 1) with <i>Aphanes arvensis</i>, 2) typical, 3) with <i>Geranium dissectum</i>, 4) with <i>Aethusa cynapium</i>. The variant with <i>Geranium dissectum</i>, belonging to the community with <i>Veronica persica</i>, was considered as having the most mountain character.

Effects of Glomus lamellosum on Growth, Essential Oil Production and Nutrients Uptake in Selected Medicinal Plants

The effect of Glomus lamellosum on root colonization, growth, essential oil production and composition and nutrient acquisition of Santolina chamaecyparissus , Salvia officinalis , Lavandula angustifolia , Geranium dissectum , and Origanum dictamnus was investigated. The results showed that mycorrhizal plants had significantly higher growth, essential oil production and nutrient contents compared to non-inoculated plants. The S. officinalis plants showed the highest percentage of colonization, while the S. chamaecyparissus the lowest. Similar percentage of colonization was found among the G. dissectum, L. angustifolia and O. dictamnus plants. Analysis of essential oil by GC and GC/MS showed that the effect of G. lamellosum on the main compounds in leaf essential oils was different on the plant species used. It is concluded that the use of Glomus lamellosum may allow plant growth in low fertility soils, reduce fertilizer inputs and increase aromatic plant production of essential oils, while they indicate that it may be possible to use mycorrhizae to affect the quality of the essential oil produced.

Tomato infectious chlorosis virus

<i>Tomato infectious chlorosis virus</i>

Accentuation of phosphorus limitation in Geranium dissectum by nitrogen: an ecological genomics study

AbstractGlobal climate change experiments have shown changes in productivity, phenology, species composition, and nutrient acquisition and availability; yet, the underlying mechanisms for these responses, especially in multi‐factorial experiments, are poorly understood. Altered nutrient availability is a major consequence of global change, directly due to anthropogenic nitrogen (N) deposition, and indirectly due to shifts in temperature and water availability. In the Jasper Ridge Global Change Experiment, microarrays were used to investigate the transcriptional responses of the dominant dicot, Geranium dissectum, to simulated N deposition. The transcript levels for several photosynthetic genes were elevated in plants exposed to elevated N, as has been reported previously, validating the use of microarrays under field conditions. A coordinated response of a suite of genes previously reported to be induced in response to phosphate (Pi) deficiency was observed, including genes for the glycolytic bypass pathway, which reduces ATP and Pi requirements for sugar degradation, suggesting that the plants were phosphorus (P) limited. Confirming this conclusion, foliar P levels in G. dissectum leaves were reduced to levels that are suboptimal for growth in plants grown in elevated N and elevated CO2 plots. Thus, although plants commonly produce more biomass in response to elevated N in native grasslands, this growth response may be suboptimal due to a P limitation. Foliar P levels in plants from elevated CO2 plots were also suboptimal for growth. However, genes indicative of Pi deficiency were not significantly expressed at higher levels. Transcript levels for genes involved in nitrate uptake and assimilation were unchanged by the elevated N deposition treatment, possibly due to the combined impacts of elevated N deposition and P limitation under field conditions. These observations highlight the complexity of the impact of global climate change factors in the field.

Modeling effects of herbicide drift on the competitive interactions between weeds

AbstractHerbicides may drift onto road verges or natural areas adjacent to arable fields and affect nontarget plants. The effect of low doses of mecoprop‐P on the competitive interactions and plant community dynamics was investigated in a model system using Capsella bursa‐pastoris and Geranium dissectum as test plants. Dose–response experiments on single species showed that compared to G. dissectum, C. bursa‐pastoris was more affected by mecoprop‐P. Consequently, we expected that G. dissectum would outcompete C. bursa‐pastoris when mecoprop‐P was applied at a low dose in the competition experiment. Indeed, mecoprop‐P had a significant effect on the interspecific competitive ability of both C. bursa‐pastoris and G. dissectum. Our previous expectation, however, was not met: The interspecific competitive ability of both species increased significantly with the dose of the herbicide, and it was predicted that C. bursa‐pastoris and G. dissectum are more likely to coexist in natural habitats with low concentrations of the herbicide compared to natural habitats with relatively high concentrations. The results from the dose–response experiments on the single species and the more laborious competition experiment approach, which is assumed to mimic the dynamics of plant communities more closely, show considerable discrepancies even though the experiments were performed at the same time and in the same greenhouse. This finding generally reduces the credibility of using single‐species tests in ecological risk assessment of herbicide use.

MODELLING EFFECTS OF HERBICIDE DRIFT ON THE COMPETITIVE INTERACTIONS BETWEEN WEEDS

Herbicides may drift onto road verges or natural areas adjacent to arable fields and affect nontarget plants. The effect of low doses of mecoprop-P on the competitive interactions and plant community dynamics was investigated in a model system using Capsella bursa-pastoris and Geranium dissectum as test plants. Dose-response experiments on single species showed that compared to G. dissectum, C. bursa-pastoris was more affected by mecoprop-P. Consequently, we expected that G. dissectum would outcompete C. bursa-pastoris when mecoprop-P was applied at a low dose in the competition experiment. Indeed, mecoprop-P had a significant effect on the interspecific competitive ability of both C. bursa-pastoris and G. dissectum. Our previous expectation, however, was not met: The interspecific competitive ability of both species increased significantly with the dose of the herbicide, and it was predicted that C. bursa-pastoris and G. dissectum are more likely to coexist in natural habitats with low concentrations of the herbicide compared to natural habitats with relatively high concentrations. The results from the dose-response experiments on the single species and the more laborious competition experiment approach, which is assumed to mimic the dynamics of plant communities more closely, show considerable discrepancies even though the experiments were performed at the same time and in the same greenhouse. This finding generally reduces the credibility of using single-species tests in ecological risk assessment of herbicide use.

Spontaneous vegetation dynamics and restoration prospects for limestone quarries in Lebanon

Abstract. In terms of restoration planning, the analysis of natural regeneration processes represents a valuable starting point for the selection of suitable species to be used. This paper aims to identify colonizing key species among the pioneer vegetation of limestone quarries in Lebanon, to identify potential restoration strategies in terms of reconstitution of the pre‐mining vegetation cover. Characteristics of the major ground colonizers after disturbance were identified in a representative quarry in the thermo‐Mediterranean biozone. The floristic inventories resulted in a matrix of cover values of 107 species × 14 plots. Correspondence analyses were used to pinpoint similarities in the distribution of key species among the different environmental characteristics of sites. The main results reveal a heterogeneous floristic composition along the regeneration gradient, where annual R‐strategy taxa such as Inula viscosa and Ainsworthia cordata dominate on very perturbed and degraded sites. Less degraded areas within the quarry were rich in herbaceous perennial or shrub species such as Geranium dissectum, Stachys distans, Salvia triloba and Ptilostemon chamaepeuce. On relatively non‐degraded areas woody and shrub perennials such as Pinus brutia, Pistacia palaestina and Quercus calliprinos dominate, along with less stress tolerant taxa such as Arbutus andrachne and Cistus creticus. Species to be used in restoration projects should be chosen from among the local vegetation, according to frequency of occurrence during the whole succession process which will reflect their adaptability to local conditions and their relevance to restoration objectives.

Effects of an Entomopathogenic Nematode and a Nuclear Polyhedrosis Virus on Emergence of Heliothis virescens (Lepidoptera: Noctuidae)

Cage tests were conducted during the 1993 growing season to determine the effect of incorporating an entomopathogenic nematode (Steinernema riobravis) in soil under cotton on subsequent emergence of tobacco budworm, Heliothis virescens (L.). When soil under seedling cotton was treated with 240K nematodes per m2 on 13 May, the number of moths emerging in cages was reduced by an average of 66%, compared to the untreated control, for at least 21 days following application. When a similar rate was applied on soil under mature cotton on 12 July, the number of moths emerging in treated cages after developing as larvae on the plants was 57% less over a 39 d period compared to the untreated control. In another cage study, application of the nematodes on wild geranium, Geranium dissectum L., an early-season host of tobacco budworms and cotton bollworms, Helicoverpa zea (Boddie), reduced adult emergence by 36% compared to untreated areas, whereas a single application of baculovirus from the celery looper (600 billion polyhedra per ha) reduced the emergence by 56%. In this latter test, adult emergence was further reduced (73% less than control) when a whitening agent was added to the virus application. These studies indicate than an entomopathogenic nematode, and the use of a whitening agent with baculovirus, might be useful in tobacco budworm management programs.