Serpentine ecotypic differentiation in a polyploid plant complex: shared tolerance to Mg and Ni stress among di- and tetraploid serpentine populations of <Emphasis Type="Italic">Knautia arvensis</Emphasis> (Dipsacaceae)

Background and aims

Serpentine soils impose limits on plant growth and survival and thus provide an ideal model for studying plant adaptation under environmental stress. Despite the increasing amount of data on serpentine ecotypic differentiation, no study has assessed the potential role of polyploidy. We tested for links between polyploidy and the response to serpentine stress in Knautia arvensis, a diploid-tetraploid, edaphically differentiated complex.

Methods

Variation in growth, biomass yield and tissue Mg and Ni accumulation in response to high Mg and Ni concentrations were experimentally tested using hydroponic cultivation of seedlings from eight populations of different ploidy and edaphic origin.

Results

Regardless of ploidy level, serpentine populations exhibited higher tolerance to both Mg and Ni stress than their non-serpentine counterparts, suggesting an adaptive character of these traits in K. arvensis. The effect of ploidy was rather weak and confined to a slightly better response of serpentine tetraploids to Mg stress and to higher biomass yields in tetraploids from both soil types.

Conclusions

The similar response of diploid and tetraploid serpentine populations to edaphic stress corresponded with their previously described genetic proximity. This suggests that serpentine tolerance might have been transmitted during the local autopolyploid origin of serpentine tetraploids.

     

Laboratory tests of oviposition by the African malaria mosquito, <Emphasis Type="Italic">Anopheles gambiae</Emphasis>, on dark soil as influenced by presence or absence of vegetation

Background

Physical objects like vegetation can influence oviposition by mosquitoes on soil or water substrates. Anopheles gambiae s. l. is generally thought to utilize puddles over bare soil as its prime larval habitat and to avoid standing water populated with vegetation. In Kisian, Kenya near Kisumu, water often pools in grassy drainage areas both during and after periods of infrequent rains, when typical puddle habitats become scarce because of drying. This raised the question of whether An. gambiae has the behavioural flexibility to switch ovipositional sites when puddles over bare soil are unavailable.

Methods

To test whether presence and height of grasses influenced oviposition, wild-caught gravid An. gambiae s. l. were offered paired choices between wet, bare soil and wet soil populated with mixed grasses or grasses of differing height. No-choice tests were also conducted by giving females either grassy soil or bare soil.

Results

In choice tests, females laid four times more eggs on bare, wet soil than soil populated with grasses. However in no-choice tests, egg output was not significantly different whether grasses were present or not. Females laid significantly more eggs on soil populated with short grass than with medium, or tall grass.

Conclusion

This work shows An. gambiae s. l. has the capacity to oviposit into grassy aquatic habitats when typical puddles over bare soil are unavailable. This knowledge will need to be considered in the design and implementation of programmes aimed at reducing malaria transmission by suppression of An. gambiae s. l. immatures.

     

Trade-off between C and N recycling and N<Subscript>2</Subscript>O emissions of soils with summer cover crops in subtropical agrosystems

Aims

Biological soil crusts (biocrusts) are soil-surface communities in drylands, dominated by cyanobacteria, mosses, and lichens. They provide key ecosystem functions by increasing soil stability and influencing soil hydrologic, nutrient, and carbon cycles. Because of this, methods to reestablish biocrusts in damaged drylands are needed. Here we test the reintroduction of field-collected vs. greenhouse-cultured biocrusts for rehabilitation.

Methods

We collected biocrusts for 1) direct reapplication, and 2) artificial cultivation under varying hydration regimes. We added field-collected and cultivated biocrusts (with and without hardening treatments) to bare field plots and monitored establishment.

Results

Both field-collected and cultivated cyanobacteria increased cover dramatically during the experimental period. Cultivated biocrusts established more rapidly than field-collected biocrusts, attaining ~82% cover in only one year, but addition of field-collected biocrusts led to higher species richness, biomass (as assessed by chlorophyll a) and level of development. Mosses and lichens did not establish well in either case, but late successional cover was affected by hardening and culture conditions.

Conclusions

This study provides further evidence that it is possible to culture biocrust components from later successional materials and reestablish cultured organisms in the field. However, more research is needed into effective reclamation techniques.

     

Endophytic infection modifies organic acid and mineral element accumulation by rice under Na<Subscript>2</Subscript>CO<Subscript>3</Subscript> stress

Background and aims

Saline and alkali soils severely impact plant growth. Endophyte and plant associations are known to significantly modify plant metabolism. This study reports the effects of a type of endophyte on organic acid (OA) accumulation and ionic balance in rice under Na₂CO₃ stress.

Methods

Rice seedlings with (E+) and without (E-) endophytic infection were subjected to different levels of Na₂CO₃ stress (0, 5, 10, 15, and 20 mM) for two weeks. Organic acids and mineral elements in the leaves and roots were determined.

Results

Seedlings with endophytic infection accumulated mainly citrate and fumarate, with some malate and succinate in the leaves. In the roots, accumulation of malate and fumarate was enhanced significantly by endophytic infection, while less citrate and succinate was accumulated under Na₂CO₃ stress, which suggested that leaves and roots use different mechanisms to control OA metabolism. Endophytes reduced the total Na and Na:K ratios, but increased ST values, the percent changes of other measured nutrients, Chl content, and dry weight per plant under Na₂CO₃ stress.

Conclusions

Endophytic infection plays a key role in maintaining plant growth by improving nutrient uptake and adjusting OA accumulation under Na₂CO₃ stress. The application of endophytes can enhance the resistance of rice to salinity.

     

High abundance of non-mycorrhizal plant species in severely phosphorus-impoverished Brazilian <Emphasis Type="Italic">campos rupestres</Emphasis>

Background and aims

We sought to describe the species and functional composition of Brazilian campos rupestres plant communities on severely nutrient-impoverished white sands, to test hypotheses relating plant communities and physiological adaptations to infertile soils. Based on recently-published information on a south-western Australian dune chronosequence, we hypothesised that campos rupestres plant communities would similarly contain a relatively large proportion of non-mycorrhizal species, because of the phosphorus-(P) impoverished nature of the soils. We also sought to test the hypothesis that many of these non-mycorrhizal species have high leaf manganese (Mn) concentrations as a consequence of carboxylate exudation to mobilise soil P.

Methods

We conducted flora surveys and quantified mycorrhizal status and foliar Mn concentrations in field sites with strongly-weathered sandy soils. Rhizosphere carboxylates were collected from glasshouse-grown plants to assess a potential correlation of carboxylates and leaf Mn concentrations.

Results

Soils were depleted of all major plant nutrients. Non-mycorrhizal plants were abundant in most field sites (mean relative cover = 48%). Vellozia species were dominant aboveground; belowground, roots were colonised more by dark septate endophytic fungi than by mycorrhizal fungi. From the field sites, foliar Mn concentrations in non-mycorrhizal species increased with decreasing soil P concentrations, but only when soil Mn concentrations were above a minimum threshold (exchangeable [Mn] above detection limit). Across all species, however, there was no relationship of foliar Mn concentrations with soil P concentrations.

Conclusions

Our hypothesis that white-sand campos rupestres communities contain a relatively large proportion of non-mycorrhizal plants was supported. Comparison with similar ecosystems in south-western Australia suggests that plant communities on severely P-impoverished sandy soils, despite differing evolutionary histories and little overlap in plant families, follow convergent evolutionary paths towards increasing abundance of non-mycorrhizal species.

     

Comparative effect of inorganic N on plant growth and N<Subscript>2</Subscript> fixation of ten legume crops: towards a better understanding of the differential response among species

Aims

A better understanding of how plant growth, N nutrition and symbiotic nitrogen fixation (SNF) are influenced by soil inorganic N availability, for a wide range of legume species, is crucial to optimise legume productivity, N₂ fixation, while limiting environmental risks such as N leaching.

Methods

A comparative analysis was performed for ten legume crops, grown in a field experiment and supplied with four N fertiliser rates. Dry matter, N concentration and SNF were measured. In parallel, root elongation rates were studied in a greenhouse experiment.

Results

For most species, N fertilisation had little effect on plant growth and N accumulation. SNF was reduced by soil inorganic N available at sowing but with large differences in the magnitude of the response among species. The response varied according to plant N requirements for growth and plant ability to retrieve inorganic N. Accordingly, root lateral expansion rate measured in RhizoTubes was highly correlated with plant ability to retrieve inorganic N measured in the field experiment.

Conclusion

Combining SNF response to soil inorganic N, shoot N and plant ability to retrieve inorganic N, allowed a robust evaluation of differential response to soil inorganic N among a wide range of legume species.

     

The use of metabolome analysis to identify the cause of an unexplained disease of Japanese gentians (<Emphasis Type="Italic">Gentiana triflora</Emphasis>)

Introduction

Gentian spotted bleaching disease (GSBD), a novel disease of unknown etiology, affects Gentiana triflora plants that are cultivated as ornamental flowers in Japan. This disease leads to the production of necrotic leaf spots, a delay in flowering, and has thus become a serious problem for gentian production.

Objectives

The objective of this study was to identify the cause of GSBD in G. triflora by analyzing differences between healthy and GSBD-affected leaves.

Method

Selected metabolite concentrations in healthy and GSBD-affected leaves were quantified using capillary electrophoresis and liquid chromatography-mass spectrometry, and statistically significant differences in metabolite concentrations were assessed. GSBD-affected metabolic pathways were identified followed by examination of pathway-related gene expression and enzyme activities. Furthermore, the effects of root hypoxia on metabolite concentrations and gene expression were investigated.

Results

We found that concentrations of Calvin cycle intermediates and ribulose 1,5-bisphosphate carboxylase/oxygenase (RubisCO) activity were significantly lower in GSBD-affected leaves, whereas sucrose cleavage and Ala accumulation were enhanced. Since these metabolic changes are frequently observed in plants exposed to hypoxia, the expression of hypoxia-responsive genes was investigated. Expression levels of hypoxia-responsive genes were higher in GSBD-affected plants than in the controls. Furthermore, root hypoxia induced similar symptoms and metabolic changes as those observed in GSBD-affected plants.

Conclusion

Our results indicate that GSBD was likely induced by root hypoxia and that metabolome analysis is an effective tool for identifying the cause of plant disease with unknown etiologies.

     

Acid and calcareous soils affect nitrogen nutrition and organic nitrogen uptake by beech seedlings (<Emphasis Type="Italic">Fagus sylvatica</Emphasis> L.) under drought,and their ectomycorrhizal community structure

Aims

The role of different soil types for beech productivity and drought sensitivity is unknown. The aim of this experimental study was to compare mycorrhizal diversity between acid sandy and calcareous soils and to investigate how this diversity affects tree performance, nitrogen uptake and use efficiency (NUE).

Methods

Beech trees were germinated and grown in five different soil types (pH 3.8 to 6.7). One-and-a-half-year-old plants were exposed for 6 weeks to sufficient or low soil humidity. Tree biomass, root tip mycorrhizal colonization and community structure, root tip mortality, leaf area, photosynthesis, nitrogen concentrations, NUE and short-term ¹⁵N uptake from glutamine were determined.

Results

Soil type did not affect photosynthesis or biomass formation, with one exception in calcareous soil, where root mortality was higher than in the other soil types. Beech in acid soils showed lower mycorrhizal colonization, higher nitrogen tissue concentrations, and lower NUE than those in calcareous soils. Drought had no effect on nitrogen concentrations or NUE but caused reductions in mycorrhizal colonization. Mycorrhizal species richness correlated with nitrogen uptake and NUE. Nitrogen uptake was more sensitive to drought in calcareous soils than in acid soils.

Conclusions

Beech may be more drought-susceptible on calcareous sites because of stronger decrease of organic nitrogen uptake than on acid soils.

     

Microbial community and associated enzymes activity influence soil carbon chemical composition in <Emphasis Type="Italic">Eucalyptus urophylla</Emphasis> plantation with mixing N<Subscript>2</Subscript>-fixing species in subtropical China

Background and aims

Microbial communities and their associated enzyme activities affect the quantity and chemical quality of carbon in soil. We aimed to evaluate the biochemical mechanisms underlying how N₂-fixing species influences soil organic carbon chemical composition through soil microbial functional groups and enzyme activities.

Methods

We examined the effects of N₂-fixing species mixed with Eucalyptus on soil carbon storage, and the chemical composition of an 8-year-old pure Eucalyptus urophylla plantation (PP) and a mixed E.urophylla and Acacia mangium plantation (MP).

Results

The soil carbon stock and recalcitrant carbon chemical component significantly increased in surface soil in MP. The total PLFAs and bacterial PLFAs increased by 29.1% and 27.0% in cool-dry season, while in the warm-wet season, the total PLFAs and bacterial PLFAs increased by 13.1% and 27.3%, respectively. However, the fungal PLFAs decreased significantly in warm-wet season in MP. The total activity of the cellulose-degrading enzyme β-glucosidase was significantly greater with mixed N₂-fixing species in both dry-cool and wet-warm season. The increase in the Alk-C/O-Alk-C ratio and SOC was strongly associated with both C-acquisition activity and bacterial community.

Conclusions

Our findings highlight the importance of N₂-fixing species in regulating both soil microbial communities and their functioning in association with soil extracellular enzyme activities, which contribute to the increased soil carbon storage and recalcitrant carbon composition in Eucalyptus plantations.

     

The bacterial community associated with rose-scented geranium (<Emphasis Type="Italic">Pelargonium graveolens</Emphasis>) leaves responds to anthracnose symptoms

Background

The fungus Colletotrichum is a plant pathogen that causes the anthracnose disease, resulting in huge losses in various crops including the rose-scented geranium (Pelargonium graveolens). Although the bacterial community associated with plants has an important role in the establishment of plant diseases, little is known about what happens in P. graveolens.

Aims

To increase the knowledge about the bacterial community associated with P. graveolens and its relationship with anthracnose disease symptoms.

Methods

Quantitative PCR and high-throughput sequencing were combined to determine the presence of the fungus Colletotrichum and to reveal the bacterial communities associated with different plant parts – root, stem and leaf – and in the rhizosphere and bulk soil, and also to determine the respective bacterial communities associated with P. graveolens leaves symptomatic and asymptomatic for anthracnose disease.

Results

The fungus Colletotrichum was detected in all plant parts and in the surrounding soil. Bacterial communities varied spatially in plants, and the disease symptoms also influenced the composition of the bacterial community. Abundances of operational taxonomic units (OTUs) assigned to the phylum Actinobacteria and to the genus Streptococcus were greatly increased in asymptomatic leaves.

Conclusions

The bacterial community associated to geranium leaves responds to anthracnose symptoms.

     

The rapid accumulation of aluminum is ubiquitous in both the evergreen and deciduous leaves of Theaceae and Ternstroemiaceae plants over a wide pH range in acidic soils

Background and aims

Aluminum (Al) accumulator plants are occasionally found in certain genera or families of woody plant species that are broadly dispersed in the angiosperm phylogeny. However, spatial and seasonal patterns in Al accumulation within the closely related species of each group remain poorly understood.

Methods

We quantitatively monitored the internal Al levels of eight Theaceae and Ternstroemiaceae species growing on acidic soils at multiple sites.

Results

Among the eight species, seven other than Ternstroemia gymnanthera shared a rapid Al accumulation in the developing leaves. Species comparison revealed that Al accumulation in mature leaves saturates within a flushing year, regardless of differences in leaf structure, seasonality, and acidic soil pH (4.5–5.5) at multiple sites. In tall trees of Stewartia monadelpha, the Al contents of the leaves were constantly high irrespective of their height positions up to 12 m. Moreover, the Al content of the leaves was only slightly decreased in the last 2 weeks of autumn senescence, in which nitrogen (N) or phosphate (P) retranslocation had been completed.

Conclusion

These results suggest that most of the Theaceae and Ternstroemiaceae species possess an effective metal-transport mechanism that rapidly loads Al into the young leaves until each level reaches a species-specific threshold.

     

Soil microalgae modulate grain arsenic accumulation by reducing dimethylarsinic acid and enhancing nutrient uptake in rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Background and aims

Microalgae are ubiquitous in paddy soils. However, their roles in arsenic (As) accumulation and transport in rice plants remains unknown.

Methods

Two green algae and five cyanobacteria were used in pot experiments under continuously flooded conditions to ascertain whether a microalgal inoculation could influence rice growth and rice grain As accumulation in plants grown in As-contaminated soils.

Results

The microalgal inoculation greatly enhanced nutrient uptake and rice growth. The presence of representative microalga Anabaena azotica did not significantly differ the grain inorganic As concentrations but remarkably decreased the rice root and grain DMA concentrations. The translocation of As from roots to grains was also markedly decreased by rice inoculated with A. azotica. This subsequently led to a decrease in the total As concentration in rice grains.

Conclusions

The results of the study indicate that the microalgal inoculation had a strong influence on soil pH, soil As speciation, and soil nutrient bioavailability, which significantly affected the rice growth, nutrient uptake, and As accumulation and translocation in rice plants. The results suggest that algae inoculation can be an effective strategy for improving nutrient uptake and reducing As translocation from roots to grains by rice grown in As-contaminated paddy soils.

     

The effect of 1,25-dihydroxyvitamin D<Subscript>3</Subscript> on TSLP,IL-33 and IL-25 expression in respiratory epithelium

Background

Airway epithelium is an active and important component of the immunological response in the pathophysiology of obstructive lung diseases. Recent studies suggest an important role for vitamin D₃ in asthma severity and treatment response.

Objective

Our study evaluated the influence of an active form of vitamin D₃ on the expression of selected mediators of allergic inflammation in the respiratory epithelium.

Material and Methods

Primary nasal and bronchial epithelial cells were exposed to1,25D₃ for 1 hour and were then stimulated or not with IL-4, TNF-α, LPS, and poly I:C. After 24 hours TSLP, IL-33, and IL-25 protein levels were measured in culture supernatants usingELISAandmRNAlevels in cells by real time PCR.

Results

1,25D₃ increased TSLP concentration in unstimulated nasal epithelial cells, but did not influence IL-33 and IL-25 expression. In IL-4-stimulated epithelial cell cultures 1,25D₃ mostly inhibited TSLP and IL-33 expression. In LPS-treated cultures 1,25D₃ decreased IL-33 expression. Simultaneously 1,25D₃ augmented IL-25 production in the same model of stimulation.

Conclusion

Our study revealed the dual nature of vitamin D₃ manifested in both pro- and anti-inflammatory properties observed in airway epithelial cells.

     

Nitrogen deposition decreases the benefits of symbiosis in a native legume

Aims

Anthropogenic nitrogen deposition can provide legumes with a cheap source of nitrogen relative to symbiotic nitrogen fixation, leading to the potential breakdown of this critical symbiosis. Here, the effects of nitrogen deposition were tested on a native symbiosis between legumes and rhizobia.

Methods

Deposition rates, soil nitrogen concentration, and plant nitrogen isotopic composition were quantified along a predicted deposition gradient in California. Acmispon strigosus seedlings were exposed to fertilization spanning nitrogen concentrations observed in the plant’s California range. Both wild and experimental plants from pristine and nitrogen polluted sites were tested using rhizobial strains that varied in nitrogen fixation.

Results

Deposition intensity was tightly correlated with nitrogen concentration in soils. The growth benefits of rhizobial nodulation were dramatically reduced by even modest levels of mineral nitrogen, and all Acmispon lines failed to form root nodules at high nitrogen concentrations.

Conclusions

Our dataset suggests that anthropogenic deposition has greatly increased soil nitrogen concentrations in Southern California leading to significantly reduced benefits of rhizobial symbiosis. If nitrogen deposition increases continue, plant host mortality and a total collapse of the symbiosis could result.

     

Interaction between contrasting rice genotypes and soil physical conditions induced by hydraulic stresses typical of alternate wetting and drying irrigation of soil

Background and aims

Drought events, agricultural practices and plant communities influence microbial and soil abiotic parameters which can feedback to fodder production. This study aimed to determine which soil legacies influence plant biomass production and nutritional quality, and its resistance and recovery to extreme weather events.

Methods

In a greenhouse experiment, soil legacy effects on Lolium perenne were examined, first under optimal conditions, and subsequently during and after drought. We used subalpine grassland soils previously cultivated for two years with grass communities of distinct functional composition, and subjected to combinations of climatic stress and simulated management.

Results

The soil legacy of climatic stress increased biomass production of Lolium perenne and its resistance and recovery to a new drought. This beneficial effect resulted from higher nutrient availability in soils previously exposed to climatic stresses due to lower competitive abilities and resistance of microbial communities to a new drought. This negative effect on microbial communities was strongest in soils from previously cut and fertilized grasslands or dominated by conservative grasses.

Conclusion

In subalpine grasslands more frequent climatic stresses could benefit fodder production in the short term, but threaten ecosystem functioning and the maintenance of traditional agricultural practices in the long term.

     

Sublethal concentration of H<Subscript>2</Subscript>O<Subscript>2</Subscript> enhances the protective effect of mesenchymal stem cells in rat model of spinal cord injury

Objective

To investigate the effect of H₂O₂ on the migration and antioxidant defense of mesenchymal stem cells (MSCs) and the neurotrophic effects of H₂O₂-treated MSCs on spinal cord injury (SCI).

Results

Sublethal concentrations of H₂O₂ decreased cell migration and expression of CXCR4 and CCR2 as well as Nrf2 expression in MSCs. In the second phase, transplantation of treated and untreated MSCs to SCI caused minor changes in locomotor dysfunction. There was a significantly difference between cell-treated and spinal cord injury groups in expression of BDNF (brain-derived neurotrophic factor). Transplantation of H₂O₂-treated cells caused an increase in BDNF expression compared to non-treated cells.

Conclusion

Transplantation of H₂O₂-treated stem cells may have protective effects against SCI through by increasing neurotrophic factors.

     

Overexpression of barley nicotianamine synthase 1 confers tolerance in the sweet potato to iron deficiency in calcareous soil

Background and aims

Iron (Fe) is an essential micronutrient for all higher organisms. Fe is sparingly available in calcareous soils and Fe deficiency is a major agricultural problem worldwide. Nicotianamine (NA) is a metal chelator involved in metal translocation in plants. Sweet potato is an attractive crop that can grow in poor soil and thus is useful for planting in uncultivated soil. In addition, the sweet potato has recently been suggested as a source of bioethanol. Our aim is to increase NA concentration in sweet potato to ameliorate Fe deficiency.

Method

Sweet potato plants expressing the barley NA synthase 1 (HvNAS1) gene under the control of CaMV 35S promoter were produced by Agrobacterium-mediated transformation.

Results

The transgenic sweet potato exhibited tolerance to low Fe availability when grown in calcareous soil. The level of tolerance to low Fe availability was positively correlated with the HvNAS1 expression level. The NA concentration of the transgenic sweet potato leaves was up to 7.9-fold greater than that of the non-transgenic (NT) plant leaves. Furthermore, the Fe and zinc concentrations were 3- and 2.9-fold greater, respectively, in transgenic sweet potato than in NT plant leaves.

Conclusions

Our results suggest that increasing the NA concentration of sweet potato by overexpression of HvNAS1 could significantly improve agricultural productivity and energy source.

     

Effectiveness of fractional CO<Subscript>2</Subscript> laser in women with stress urinary incontinence

Background

Stress urinary incontinence (SUI) is a relatively common disorder that significantly affects the quality of life. Many conservative and surgical treatment methods have been recommended for SUI, but they have major limitations.

Aims

To assess the use of the CO₂ fractional laser in the treatment of SUI.

Methods

This clinical trial included 55 patients with confirmed SUI. Patients underwent fractional CO₂ laser treatment 3 times at 30-day intervals. Data on age, smoking history, sexual activity, menopause, and history of hormone replacement therapy (HRT) were collected. Response to treatment was assessed by SUI severity and the level of sexual satisfaction was assessed using the visual analog scale (VAS). Patients were evaluated at 3 different time points: before treatment, and 45 days and 6 months after the last laser treatment.

Results

The mean patient age was 44.4±11.4 years (range: 28 to 68 years). Smoking history was positive in 6 patients (9.1%); 19 (54.3%) were menopausal on HRT. The SUI severity score at baseline (before treatment) was 8.56±0.62 and decreased to 2.28 6 months after treatment (p<0.0001). The sexual satisfaction score was 3±0.94 at baseline and increased to 7.87±0.93 6 months after treatment (day 180) (p<0.0001, slope = + 2.2)

Conclusion

Our findings are in line with a previous study that showed the value of transvaginal CO₂ fractional laser treatment for alleviation of SUI symptoms and its potential as an alternative treatment. We also observed improved sexual satisfaction in SUI patients.