Medicago Marina Research Articles

Microemulsion of Medicago marina Essential Oil: In Vitro Evaluation of Antimicrobial, Antibiofilm, Anticoagulant Effects, and In Silico Studies Involving Molecular Docking and ADME Prediction

This work characterizes microemulsions of Medicago marina essential oil and evaluates their antimicrobial, antibiofilm, and anticoagulant effects. Medicago marina L. aerial parts essential oil was hydro-distilled and analyzed by gas chromatography-FID and gas chromatography/mass spectrometry (GC/MS) for the first time from the Tunisian chemotype. The microemulsion was prepared using an oil/water formulation with a biopolymer (Arabic gum) and surfactant (Tween 20). Antibacterial and antifungal activities were evaluated using the microbroth dilution method, while anticoagulant activity was tested in vitro using prothrombin time (PT) and aPTT tests. Eventually, the binding affinities and molecule’s interactions of the main chemicals with the operational locations of C (30) carotenoid dehydrosqualene synthase and cytidine deaminase were explored. The essential oil contained 71 compounds of which 87.6% were identified. Major compounds were [Formula: see text]-ionone (17.67%), 1-methyleugenol (10.75%), eugenol (8.86%), [Formula: see text]-damascenone (4.33%), and [Formula: see text]-humulene (4.32%). A microemulsion with a diameter of 1.63 [Formula: see text] m, a polydispersity index of 0.17, a zeta potential of –40.8 mV and a pH of 6 was obtained and it showed the highest antibacterial potential against a multitude of microbes, with low MICs varying between 0.406 mg/mL and 3.25 mg/mL. Significant antibiofilm activity was observed with over 80% inhibition at 4 × MIC concentration. It showed better anticoagulant activity than heparin, with PT and aPTT values of 19.5 s and 57 s, respectively, at 10 mg/mL. Molecular docking showed that “([Formula: see text]-[Formula: see text]-ionone” had the highest binding scores. Notable pharmacokinetic and drug-like qualities were found in the obtained molecules after establishing ADME profiling. As a result, Medicago marina L. Essential oil microemulsion can be used in food processing as a preservative.

A Comparative Study of the Influence of Soil and Non-Soil Factors on Seed Germination of Edible Salt-Tolerant Species

Cultivating edible salt-tolerant plants (halophytes) for human consumption is increasingly important due to climate change and soil salinization, and offers sustainable agricultural solutions. Optimizing seed germination, the crucial initial stage of crop growth, is essential for enhancing crop production. This study aimed to optimize the germination of edible halophytes under greenhouse conditions, focusing on select soil (salinity and substrate) and non-soil-related factors (chemical and mechanical treatments). The target species were selected for their commercial value and included Mesembryanthemum crystallinum L. (crystalline iceplant), Salicornia ramosissima J. Woods (sea asparagus), Medicago marina L. (sea medick), Ammophila arenaria (L.) Link (European beachgrass), Portulaca oleracea L. (common purslane), and Atriplex halimus L. (Mediterranean saltbush). Salinity negatively impacted germination rates (GRs) and delayed mean germination time (MGT) across species. P. oleracea had the highest GR (95.6%) in coco peat under freshwater irrigation, and the shortest MGT (5.2 days). A. halimus did not germinate under the tested conditions. Scarification with sulfuric acid improved the GR of M. marina by 42.2%, while scarification with ultrasounds improved the GR of A. arenaria by 35.5%. Our results indicate that the choice of substrate and the application of specific treatments like scarification can significantly improve the germination of certain halophyte species under variable saline conditions.

Effect of glyphosate on germination and seedling development of four native plants of dunes in Spain

Using glyphosate is easier than manually controlling the invasive plant Carpobrotus in dune ecosystems. However, before it is used its effect on native species in this ecosystem needs to be determined. This study reports the effects in the laboratory of different concentrations of glyphosate (1.0, 0.5, 0.3, 0.1, 0.05, 0.01, and 0.005 g/m2 ) on germination and seedling emergence of four species of Mediterranean dune plants, Lotus creticus, Medicago marina, Ononis ramosissima and Ammophila arenaria, used in the restoration of this natural ecosystem. Germination was completely inhibited when glyphosate was applied at 0.5, and 1.0 g/m2. The recommended dose (0.3 g/m2 ) also inhibited the germination of L. creticus and M. marina. The percentage germination of O. ramosissima and A. arenaria was around 40% and 30% respectively when a dose of glyphosate of 0.1 g/m2 was used, whereas for seeds of L. creticus and M. marina it was lower than 5%. The T50 at germination of seed incubated with glyphosate increased in all species independently of the dose of glyphosate. Seedling emergence from seeds previously germinated in the presence of glyphosate was only recorded for O. ramosissima and A. arenaria. The results indicate that seeds of O. ramosissima are more tolerant of glyphosate, followed by those of A. arenaria and those of L. creticus and M. marina are the most sensitive.

Triterpenic saponins from Medicago marina L

The saponin composition of leaves and roots from Medicago marina L., sea medic, was investigated by a combination of chromatographic, spectroscopic and spectrometric (GC, LC, ESI-MS/MS, NMR) methods. Several compounds were detected and quantified by HPLC using the external standard method. Saponins from this plant species consist of a mixture of high molecular weight bidesmosidic derivatives of medicagenic and zanhic acid, containing up to six sugars in the molecules. Six of the detected saponins were previously isolated and reported as constituents of other Medicago spp.; one saponin was previously described in other plant species; four saponins are undescribed compounds in Medicago and never reported before in other plant species. These are: 3-O-β-D-glucopyranosyl-(1 → 2)-β-D-glucopyranosylzanhic acid 28-O-β-D-xylopyranosyl-(1 → 4)-[β-D-apiofuranosyl-(1 → 3)]-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyl ester; 3-O-β-D-glucopyranosyl-(1 → 2)-β-D-glucopyranosylzanhic acid 28-O-β-D-xylopyranosyl-(1 → 4)-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyl ester; 3-O-β-D-glucopyranosyl-(1 → 2)-β-D-glucopyranosylmedicagenic acid 28-O-β-D-xylopyranosyl-(1 → 4)-[α-L-arabinopyranosyl-(1 → 3)]-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyl ester and 3-O-β-D-glucopyranosylmedicagenic acid 28-O-β-D-xylopyranosyl-(1 → 4)-[α-L-arabinopyranosyl-(1 → 3)]-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranosyl ester. The specific saponins synthesized by M. marina may have a role in its tolerance to environment, representing a reservoir of osmolytic sugars.

Diversity of Sinorhizobium (Ensifer) meliloti Bacteriophages in the Rhizosphere of Medicago marina: Myoviruses, Filamentous and N4-Like Podovirus.

Using different Sinorhizobium meliloti strains as hosts, we isolated eight new virulent phages from the rhizosphere of the coastal legume Medicago marina. Half of the isolated phages showed a very narrow host range while the other half exhibited a wider host range within the strains tested. Electron microscopy studies showed that phages M_ort18, M_sf1.2, and M_sf3.33 belonged to the Myoviridae family with feature long, contractile tails and icosaedral head. Phages I_sf3.21 and I_sf3.10T appeared to have filamentous shape and produced turbid plaques, which is a characteristic of phages from the Inoviridae family. Phage P_ort11 is a member of the Podoviridae, with an icosahedral head and a short tail and was selected for further characterization and genome sequencing. P_ort11 contained linear, double-stranded DNA with a length of 75239 bp and 103 putative open reading frames. BLASTP analysis revealed strong similarities to Escherichia phage N4 and other N4-like phages. This is the first report of filamentous and N4-like phages that infect S. meliloti.

The impact on plant communities of an invasive alien herb, Oenothera drummondii, varies along the beach-coastal dune gradient

One of the major threats to the diversity of coastal dunes is the expansion of invasive species, such as Oenothera drummondii subsp. drummondii (Onagraceae). In southwestern Spain, we studied the impact of this American invasive on community structure and composition along a beach-dune gradient (beach, foredune, and inland dunes). Differences in density, biomass, and the cover of O. drummondii, the cover of perennial and annuals/biennials species, and Shannon diversity index H’ and dominance λ were compared between invaded and uninvaded sectors. We observed that the intensity and impact of the invasion by O. drummondii varies along the beach-dune gradient. The abundance of the invasive plant increased inland and in consequence, its impact on species richness and composition was highest in inland dunes. Here, plant cover of O. drummondii represented 57.9% of total plant cover; species richness was reduced (with 3.3 fewer species per 2 × 2m plot), diversity H’ was lower while dominance λ was higher. At a broader scale, species richness in the invaded sector was 25% larger than in the uninvaded sector, because of the presence of ruderal species. Species composition also was modified after the invasion. The abundance of a keystone native species was largely reduced (Ammophila arenaria), and some natives became locally extinct (Otanthus maritimus, Eryngium maritimum, Medicago marina and Elymus farctus). We conclude that the high environmental severity of the beach and foredunes results in a reduced invasion and impact of O. drummondii, whereas the milder conditions of inland dunes promote its expansion. The shift in community structure and composition can have an increasing domino effect and thus monitoring, and mitigation actions are necessary. When doing so, the environmental heterogeneity of the beach-dune gradient should be considered, given its relevance in the invasion process.

Spatiotemporal Distribution and Sources of Trace Elements in Ave River (Portugal) Lower Basin: Estuarine Water, Sediments and Indigenous Flora

This study aimed to assess the spatial and seasonal distribution and anthropogenic sources of trace elements (Li, Be, Al, V, Cr, Co, Ni, Cu, Zn, Se, Mo, Ag, Cd, Sb, Ba, Tl, Pb, and U) by ICP-MS in the Ave River lower basin, Portugal. Mean values (µg L−1) of Al (2384), Zn (55.3), Se (34.6), Cu (24.7), Pb (12.7), Ag (0.75), and Cd (0.66), exceeded the water quality guidelines for the protection of aquatic life. The decreasing order of trace elements concentrations in surface water and sediments was, respectively: Al > Zn > Se > Mo > Li > Ba > V > Cu > Pb > Ni > Cr > U > Be > Co ≈ Sb > Ag ≈ Cd > Tl; and Al > Zn > Li > Ba > Cu > Pb > Cr > V > Ni > Co > U > Be > Se ≈ Mo ≈ Tl ≈ Cd ≈ Sb ≈ Ag. Moreover, the concentrations of nitrate values were higher than 50 mg L−1. To distinguish natural from anthropogenic sources, the geo-accumulation index (Igeo) and the enrichment factor (EF) of sediments were determined. Igeo revealed high contamination by Al, Mn, Ba and Zn, while EF evidenced enrichment for Se, Cd, Zn, Li, Cu, Ag, Pb and U. Bioaccumulation factors (BF) in flora suggested that macroalgae, Medicago marina L. and Plantago lanceolata L., might be accumulators of Se, Mo, Ba and Pb (BF > 1). The highest translocation factor (TF) was found for Mo in leaves (33.6) and flowers (28.1) of P. lanceolata L..

Can coastline plant species be used as biosamplers of emerging contaminants? - UV-filters and synthetic musks as case studies

Personal care products, an important class of emerging contaminants, have been frequently detected in different environmental matrices. Included in this category are synthetic musks compounds (SMCs) and UV-filters. Their occurrence in the coastal environment has been poorly studied. Therefore, this work aimed to verify whether five coastline plant species (Carpobrotus edulis, Cakile maritima, Medicago marina, Elymus farctus borealis-atlanticus and Euphorbia paralias) have the ability to accumulate 11 SMCs (cashmeran, celestolide, phantolide, galaxolide, tonalide, exaltolide, musk moskene, tibetene, ambrette, xylene and ketone) and 2 organic UVB filters (3-(4′-methylbenzylidene) camphor and octocrylene), functioning as biosamplers. To accomplish this task, a QuEChERS technique (“Quick, Easy, Cheap, Effective, Rugged, and Safe”) was employed to extract the target compounds from the plant material collected in 15 beaches of Matosinhos and Vila Nova de Gaia (Portugal). The resulting extracts were analysed by gas chromatography–mass spectrometry. Limits of detection ranged from 0.02 ng g−1 for celestolide and tonalide to 1.32 ng g−1 for musk ambrette. The obtained recoveries were around 93% and relative standard deviation was generally less than 15%. SMCs were detected at levels ranging from 1.56 to 350 ng g−1 dw and UV-filters from 2.9 to 264 ng g−1 dw. Galaxolide and 3-(4′-methylbenzylidene) camphor were the synthetic musk and UV-filter detected in higher concentrations, respectively.Plants with higher water content accumulate better SMCs (hottentot-fig), while those with higher lipid content retain better the UV-filters (sea spurge).

Rhizobial strains isolated from nodules of Medicago marina in southwest Spain are abiotic-stress tolerant and symbiotically diverse

The isolation and characterisation of nitrogen-fixing root nodule bacteria from Medicago marina, a tolerant legume species, were studied in two areas from southwest Spain. A total of 30 out of 82 isolates with distinct ERIC-PCR fingerprints were analysed on the basis of molecular (PCR-RFLP of the 16S-23S rDNA intergenic spacer region (IGS) with two endonucleases, analysis of the 16S rDNA and symbiotic nodC gene sequences, plasmid profiles and SDS-PAGE of LPS, including the partial sequence of the housekeeping gene glnII and the symbiotic gene nodA of some representatives), physiological (utilisation of sole carbon sources, tolerance to antibiotics, NaCl, heavy metals, temperature and pH) and symbiotic parameters (efficacy on M. marina, M. minima, M. murex, M. orbicularis, M. polymorpha, M. sativa and M. truncatula). All the bacteria isolated from M. marina nodules belonged to Ensifer meliloti, except for one strain that belonged to E. medicae. To determine the nodulation range of M. marina, 10 different Ensifer species were tested for their ability to nodulate on this plant. E. kummerowiae CCBAU 71714 and the E. medicae control strain M19.1 were the only Ensifer species tested that developed nitrogen-fixing nodules on this plant. Most of the M. marina-nodulating strains showed tolerance to stress factors and all of them shared the presence of a gene similar to cadA, a gene that encodes for a PIB-type ATPase, which is a transporter belonging to the large superfamily of ATP-driven pumps involved in the transport of metals across cell membranes.

Persistence of Centaurea pumilio L., a rare sand dune species

The persistence of C. pumilio L. (Asteraceae) in time is an issue which is fundamental for conservation measures since the species is rare and often endangered. Therefore we tried to evaluate persistence as a consequence of plant longevity and its survival capacity. We estimated species’life-span by counting the number of rings present in root. Because species survival in time is guaranteed by availability of seeds in the habitat and their presence in soil seed banks, we studied the germination capacity of old seeds under light and in the dark and therefore their potential to remain viable through time. For better understanding of C. pumilio’s germination strategy, we additionally studied germination of two sand dune species commonly found together with C. pumilio : Cakile maritima Scop. and Medicago marina L. for comparison. According to our results the persistence of C. pumilio is guaranteed by the long-living mother plant, since we recorded specimen older than 50 years. On the other hand, species’rarity is the result of lacking mechanisms, which would prevent C. pumilio seeds to germinate at high rate under sunlight and thereby exposing seedlings to extreme conditions.

Assessing Genotypic Diversity and Symbiotic Efficiency of Five Rhizobial Legume Interactions Under Cadium Stress for Soil Phytoremediation

In the framework of soil phytoremediation using local legume plants coupled with their native root-nodulating bacteria to increase forage yields and preserve contaminated soils in arid regions of Tunisia, we investigated the diversity of bacteria from root nodules of Lathyrus sativus, Lens culinaris, Medicago marina, M. truncatula, and M. minima and the symbiotic efficiency of these five legume symbiosis under Cadmium stress. Fifty bacterial strains were characterized using physiological and biochemical features such heavy metals resistant, and PCR-RFLP of 16S rDNA. Taxonomically, the isolates nodulating L. sativus, and L. culinaris are species within the genera Rhizobium and the ones associated to Medicago sp, within the genera Sinorhizobium. The results revealed also that the cadmium tolerance of the different legumes-rhizobia interaction was as follows: M. minima<M. truncatula<M. marina<L. sativus<L. culinaris indicating that the effect of Cadmium on root nodulation and biomass production is more deleterious on M. minima-S. meliloti and M. truncatula-S. meliloti than in other symbiosis. Knowledge on genetic and functional diversity of M. marina, L. sativus and L. culinaris microsymbiotes is very useful for inoculant strain selection and can be selected to develop inoculants for soil phytoremediation.

Sand Dune Species Distribution and Size Variations in Two Areas Inside a Natural Protected Area Subjected to Different Human Disturbance

Sand dune species were analyzed across two areas included in the “Roman Coastal State Nature Reserve” (Italy): Ostia (O) and Marina di Palidoro (P). Significant variations in species distribution, dry mass and size over the gradient from the water-edge toward the inland between O and P were observed. Species colonize O, on an average, at 79 m from the water-edge extended along the gradient toward the inland over a length of 26 m. PD is 40.8 ± 9.9 plants.m-2. Ononis variegata and Elymus farctus have the highest PD (15.4 ± 1.3 plants.m-2), followed by Silene colorata and Sporobulus pungens (4.3 ± 3.9 plants.m-2), by Cakile maritima, Echinophora spinosa, Eryngium maritimum, Ammophila arenaria, Anthemis maritima, Cyperus capitatus, Medicago marina and Calystegia soldanella (.m-2), with C. soldanella having the lowest PD (0.02 plants.m-2). On an average, in P, the species colonize the dune at 17 m from the water-edge for a length of 46 m toward the inland, PD is on an average 21.5 ± 16.1 plants.m-2. S. pungens, E. farctus and O. variegata have the highest PD (6.0 ± <span style="fon

Do Halophytes Really Require Salts for Their Growth and Development? An Experimental Approach

Halophytes are salt-tolerant plants found exclusively in habitats with high levels of soil salinity. It is generally assumed that salt stress is the most important limiting factor for plant growth in natural saline environments, and that halophytes have developed specific adaptations to elevated salinity which make them unfitted to grow in the absence of salt, thus explaining their distribution in nature. To address experimentally this question, two halophytic species (Inula crithmoides L. and Plantago crassifolia Forssk.) and a maritime dune species (Medicago marina L.) were grown in the greenhouse for several weeks in different substrates: peat, vegetable garden soil, saline soil and sand from maritime dunes. Measurements of growth parameters-number of leaves, plant length, fresh and dry weights-showed that all three species grew much better on the salt-free and nutrient-rich substrates, peat and garden soil, than on saline soil and dune sand. These results indicate that salts are not compulsorily required for development of halophytic species, and suggest that limitation of water and nutrients, rather than soil salinity per se, are the most important restrictive factors for plant growth in saline habitats. The distribution of halophytes in nature is probably dependent on their limited ability to compete with glycophytes in non-saline areas, while remaining highly competitive under environmental conditions stressful for non-tolerant species.

Estrogenic activity of the methanolic extract of Ebenus cretica L

Plant derived compounds when friendly to the human organism tend to become very important ingredient of our nutrition. Members of the Leguminosae family are known to exhibit a mild estrogenicity due to their rich phenolic profile. In the present study, methanolic extracts of Ebenus cretica L. (ECME), Ebenus sibthorpii DC., Medicago marina L. (MMME) and Medicago falcata L. have been investigated for their estrogenic activity on ERb. All extracts were subjected to ERβ-binding screening using stably transfected HeLa cells. Luciferase assay was used as a tool to monitor the ERβ-binding. At the concentration of 400µg/ml ECME and MMME exhibit 2.7-fold and 3.2-fold respectively stronger binding with the ERβ compared to its natural agonist, estradiol. Followingly, in order to isolate bioactive compounds from E. cretica, ECME was submitted to fast centrifugal partition chromatography and sephadex analysis and was proved rich in flavonoids such as rutin and isoflavones such as 4', 8-dimethylether-7-O-β-D-glucopyranosylisoflavone. An aurone, maesopsin glucoside, was also isolated. Additionally, an in vivo experiment was performed in order to evaluate ECME's osteoprotective role. Female Wistar rats were treated with the ECME dissolved in drinking water. Rats were submitted to ovariectomy prior to the treatment.

Dormancy of Medicago marina (L.) seed

Medicago marina (L.) is a Mediterranean species whose seeds show strong dormancy that prevents germination. We used an integrated approach of physiological analyses and proteomics to investigate the mechanisms that control M. marina dormancy/germination and that underlie stress tolerance. First, we evaluated the effects on dormancy breaking of the following treatments: mechanical scarification, freezing at −20 °C, storage for 4 months and heating at 100 °C for 1 h. Mechanical scarification and freezing were the most effective treatments in overcoming dormancy. The role of abscisic acid (ABA) in M. marina dormancy was studied by ELISA immuno-enzymatic assay. The ABA content of germinated and non-germinated mature (control) and treated seeds was determined. The level of ABA was higher in treated seeds than in control seeds; the most significant increase occurred in the heated seeds. A comparison of the ABA level in the germinated, control and treated seeds suggests that different mechanisms modulate ABA content in response to different stresses, and that a specific ABA-signalling pathway regulates germination. Proteomic analysis revealed 46 proteins differentially expressed between treated and untreated seeds; 14 of these proteins were subsequently identified by mass spectrometry. Several of the proteins identified are important factors in the stress response, and are involved in such diverse functions as lipid metabolism, protein folding and chromatin protection. Lastly, an analysis of the phosphoproteome maps showed that the function of many proteins in seeds subjected to temperature treatment is modulated through post-translational modifications.

Greenhouse inoculation of psammophilic plant species with arbuscular mycorrhizal fungi to improve survival and early growth

Psammophilic plants are characterized for their adaptability to the hard environmental conditions of the coastal sand dune habitats that limit the survival of most vegetation. Considering that mycorrhizal plants are known to be effective colonizers of degraded habitats, the influence of the arbuscular mycorrhizal (AM) symbiosis in plant growth was studied in fifteen psammophilic plant species: Lotus creticus, Dorycnium pentaphyllum, Otanthus maritimus, Thymbra capitata, Armeria maritima, Halimium halimifolium, Ononis natrix, Medicago marina, Genista umbellata, Crucinella maritima, Elymus farctus, Ammophila arenaria, Pancratium maritimum, Glaucium flavum and Limoniastrum monopetalum. Wild seeds were used in this study to compare the effect of plant inoculation with a consortium of native AM fungi isolated from a coastal sand dune and with the selected isolate Glomus intraradices BEG 72 versus non mycorrhizal plants. After six months growth, we found that eleven of the fifteen psammophilic species responded positively to AM fungi inoculation and both root and shoot development benefited considerably from the presence of the AM fungi. We can conclude that many of the psammophilic species produced after the germination of the wild seeds collected in their natural habitats show limited growth due in part to the lack of adequate AM fungal inoculum in the plants growing substrate. AM inoculation seems to be critical for their survival.

Symbiotic diversity of Ensifer meliloti strains recovered from various legume species in Tunisia

Ensifer meliloti (formerly Sinorhizobium meliloti) was first considered as a specific microsymbiont of Medicago, Melilotus and Trigonella. However, strains of E. meliloti were recovered from root nodules of various legume species and their symbiotic status still remains unclear. Here, we further investigate the specificity of these strains. A collection of 47 E. meliloti strains isolated in Tunisia from root nodules of Medicago truncatula, Medicago sativa, Medicago ciliaris, Medicago laciniata, Medicago marina, Medicago scutellata, Phaseolus vulgaris, Cicer arietinum, Argyrolobium uniflorum, Lotus creticus, Lotus roudairei, Ononis natrix, Retama raetam, Genista saharae, Acacia tortilis, Hedysarum carnosum and Hippocrepis bicontorta were examined by REP-PCR fingerprinting, PCR-RFLPs of the 16S-23S rDNA IGS, the nifH gene and nifD-K intergenic spacer, and sequencing of 16S rRNA and nodA genes. Their nodulation range was also assessed by cross-inoculation experiments. No clear correlation was found between chromosomal backgrounds and host plants of origin. The nodulation polyvalence of the species E. meliloti was associated with a high symbiotic heterogeneity. On the basis of PCR-RFLP data from the nifH gene and nifD-K intergenic spacer, E. meliloti strains isolated from non- Medicago legumes harboured distinct genes and possessed wider host ranges. Some strains did not nodulate Medicago species. On the basis of nodA phylogeny, the majority of the Tunisian strains, including strains from Medicago, harboured distinct nodA alleles more related to those found in E. medicae than those found in E. meliloti. However, more work is still needed to characterize this group further. The diversity observed among M. laciniata isolates, which was supported by nodA phylogeny, nifH typing and the efficiency profile on M. ciliaris, indicated that what was thought to be bv. medicaginis is certainly heterogeneous.

Islands of fertility induce co-occurring negative and positive plant-soil feedbacks promoting coexistence

Positive plant-soil feedback by “ecosystem engineers” is an important driver for the structuring and organization of resource-limited ecosystems. Although ample evidence demonstrates that plant-soil feedbacks can range from positive to strongly negative, their co-occurrence in plant communities have not yet been investigated. We test the hypothesis that the plant-soil feedback generated by the nitrogen-fixer shrub Medicago marina during primary succession in a sand dune community has a positive effect on the coexisting grass Lophochloa pubescens and a negative effect on the shrub species itself. We conducted field measurements and laboratory bioassays to evaluate (1) the effects of islands of fertility on the recruitment and growth of its ecosystem engineer and on the performance of a coexisting species and (2) the mechanisms involved that can explain the opposite effects of islands of fertility on coexisting species. Islands of fertility were present under Medicago crowns evidenced by higher available nitrogen, extractable phosphorus and potassium, organic matter, microbial activity, water holding capacity, soil humidity, and lower salt concentrations. The effects of these islands of fertility were clearly species-specific, with a facilitative impact on Lophochloa and a negative effect on Medicago recruitment. Lophochloa was denser and produced more biomass when rooted inside as compared to outside the crown area of the shrub. Contrarily, the number of seedlings of Medicago was lower inside, despite the higher seed abundance, and higher outside the crown area of adult shrubs as compared to predictions based on random distribution, thus showing a Janzen-Connell distribution. Laboratory experiments demonstrate the occurrence of Medicago negative plant-soil feedback, and that the auto-toxicity of the aboveground senescent plant material is a potentially important underlying mechanism explaining this negative feedback and the resulting Janzen-Connell distribution in the field.

Composition of the essential oil of Medicago marina L. from the coastal dunes of Tuscany, Italy

AbstractThis paper discusses essential oil composition of the dried aerial parts of Medicago marina harvested before and during blossom, in Vada (Livorno, Italy). In the two essential oils, rich in carbonylic compounds, 54 components were identified. Linalool (5.8%) and α‐terpineol (3.3%) were the main monoterpenes in the vegetative phase sample, while linalool (1.2%) and p‐mentha‐4‐en‐3‐one (0.4%) in the was the main constituent flowering stage. Sesquiterpenes were present only during the flowering stage, when the main constituents were non‐terpenic substances. 1‐Octen‐3‐ol and the (E)‐β‐ionone were the two constituents which showed the greater differences between the two samples (9.3% and 0.7% for the first component and 14.4% and 5.6% for the second component in the two different phases). Furthermore, phenyl propanoids were also identified in these oils, particularly methyl eugenol during the reproductive phase and eugenol during the vegetative phase. Copyright © 2003 John Wiley &amp; Sons, Ltd.

Some Littoral Spermatophytes of the Naples Region

THE strand flora about the Bay of Naples differs so much from most of those which have been studied with reference to the toxic effect of sodium chlorid solutions that it seemed to the writer worth while to investigate the conditions of existence of a characteristic association. Along a strip of beach sand not quite two meters above the average sea level and less than ten meters from the water line, on the margin of the Bay of Baiae, a well defined association of somewhat more than fourteen members was found. All of these occurred within a distance of a hundred meters, measured along the shore. The species determined were: Euphorbia Paralias, E. terracina, Polygonum maritimum, Matthiola sinuata, *Alyssum maritimum, Plantago Coronopus, Medicago marina, M. litoralis, *Lotus ornithopodioides, Eryngium maritimum, Echinophora spinosa *Senecio vulgaris, *Artemisia variabilis, *Inula viscosa.