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Bartoli F.,CNRS Soil and Environment Laboratory | Coinchelin D.,CNRS Soil and Environment Laboratory | Robin C.,CNRS Agronomy and Environment Laboratory | Echevarria G.,CNRS Soil and Environment Laboratory
Plant and Soil | Year: 2012

Aims: The primary aim of this study was to investigate the impact of active nickel and cadmium transport, transpiration and shoot biomass production on Ni and Cd accumulation in the leaves of the Ni-hyperaccumulator Leptoplax emarginata. A secondary objective was to observe the effects of various concentrations of nickel and cadmium in solutions on the plant growth and ecophysiological characteristics of these plants. Finally, the study sought to identify possible nickel and cadmium concentration gradients in solution as a function of the root distance. Methods: The Intact Plant Transpiration Stream Concentration Factor (TSCF=xylem/solution solute concentration ratio) was determined for both Ni and Cd and for the selected intact transpiring Ni-hyperaccumulator Leptoplax emarginata, cultivated on two contrasting fertilized and Ni-Cd-contaminated sandy porous media (rhizotrons with central root compartments, linked to Mariotte tubes operated at -1 kPa). IPTSCF Ni and IPTSCF Cd were calculated as the ratios between the hyperaccumulator plant's nickel or cadmium mass in the leaves and the nickel or cadmium concentration in solution by the volume of water transpired during the period of culture. Plant growth characteristics and gas exchanges were also recorded. Results: IPTSCF values were much greater than 1 (IPTSCF Ni = 5. 2 ± 0. 9 and IPTSCF Cd = 4. 4 ± 0. 6) whatever the amount of available Ni and Cd. This characterized a predominantly active plant metal uptake. Moreover, biological regulation was reported: plant growth and transpiration were significantly lower for hyperaccumulator plants cultivated in sand which was rich in available Ni and Cd, than for hyperaccumulator plants cultivated in topsoil, poor in available Ni and Cd. In the soil rhizosphere, capillary flow was related to transpiration and a depletion pattern was developed for Ni and sometimes for Cd. Conclusions: Overall, the Intact Plant Transpiration Stream Concentration Factor appeared to be a relevant metal bioconcentration factor taking into account the predominant type of metal transport from roots to leaves, plant growth and transpiration coupling and metal availability. IPTSCF Ni and IPTSCF Cd values were much greater than 1 and similar whatever the amount of available Ni and Cd. This characterized a predominantly active plant combining Ni and Cd uptake and biological regulations dependent of the Ni and Cd concentrations in solution. © 2011 Springer Science+Business Media B.V. Source

Coinchelin D.,CNRS Soil and Environment Laboratory | Bartoli F.,CNRS Soil and Environment Laboratory | Robin C.,CNRS Agronomy and Environment Laboratory | Echevarria G.,CNRS Soil and Environment Laboratory
Journal of Experimental Botany | Year: 2012

Solute active transport or exclusion by plants can be identified by the values of the Transpiration Stream Concentration Factor (TSCFxylem:solution solute concentration ratio). The aim of this study was to estimate this parameter for Ni uptake by the Ni-hyperaccumulator Leptoplax emarginata or the Ni-excluder Triticum aestivum cultivar 'Fidel'. The Intact Plant TSCF for nickel (IPTSCFNi) was calculated as the ratio between the nickel mass accumulation in the leaves and the nickel concentration in solution per volume of water transpired. Predominantly, Ni active transport occurred for L. emarginata, with IPTSCFNi values of 4.7-7.2 and convective component proportions of the root Ni uptake flow of only 15-20% for a range of Ni concentrations in solutions of 2-16 mol Ni l-1, regardless of the growth period and the time of Ni uptake. Hyperaccumulator roots were permeable to both water and nickel (mean reflection coefficient for Ni, σNi, of 0.06), which was mainly attributed to an absence of exodermis. Results provide a new view of the mechanisms of Ni hyperaccumulation. By contrast, the wheat excluder was characterized by an extremely low mean IPTSCFNi value of 0.006, characterizing a predominantly Ni sequestration in roots. From a methodological viewpoint, the 'microscopic' TSCFNi, measured directly on excised plants was 2.4 times larger than its recommended 'macroscopic' IPTSCFNi counterpart. Overall, IPTSCF and σ determined on intact transpiring plants appeared to be very useful biophysical parameters in the study of the mechanisms involved in metal uptake and accumulation by plants, and in their modelling. © 2012 The Authors. Source

Ernoult A.,CNRS Ecosystems, Biodiversity, and Evolution Laboratory | Vialatte A.,National Polytechnic Institute of Toulouse | Butet A.,CNRS Ecosystems, Biodiversity, and Evolution Laboratory | Michel N.,CNRS Agronomy and Environment Laboratory | And 3 more authors.
Agriculture, Ecosystems and Environment | Year: 2013

In the context of rapid and severe biodiversity decline in agroecosystems, the European Union has introduced agri-environmental schemes. However, these schemes require evaluation to estimate their efficiency, for further consolidation and improvement. The establishment of grassy strips along watercourses represents a measure of cross-compliance introduced in France in 2005. In this study, we analyzed the benefits of these new landscape elements for biodiversity, by (i) exploring the plant community composition of grassy strips in relation to their landscape context, (ii) analyzing the faunal communities of three major functional groups (i.e., small mammals, syrphids, and carabid beetles) present in grassy strips of agroecosystems, (iii) comparing the faunal biodiversity to that observed in other habitats of agroecosystems, such as fields and hedgerows, and (iv) investigating the relationships between faunal community indices and grassy strip properties. The results of our study showed that the plant community of grassy strips is mainly influenced by semi-natural habitats that are present within a landscape context, i.e., at a scale >500 m. We found that grassy strips do not necessarily present areas of particularly high animal biodiversity compared to other habitats (i.e., fields and hedgerows). However, the properties of these strips (i.e., length, width and plant biodiversity) influence the structure of faunal communities. Two years after the establishment of grassy strips, their role as ecotones between previous field margins (mostly hedgerows in our study site) is illustrated through the response of the fauna. Hence, grassy strips, being more stable than cultivated fields, contribute to a new refuge within the agroecosystem landscape. © 2012 Elsevier B.V. Source

Buch F.,Max Planck Institute for Chemical Ecology | Rott M.,Max Planck Institute for Chemical Ecology | Rott M.,Max Planck Institute for Plant Breeding Research | Rottloff S.,Max Planck Institute for Chemical Ecology | And 5 more authors.
Annals of Botany | Year: 2013

Background and AimsCarnivorous plants of the genus Nepenthes possess modified leaves that form pitfall traps in order to capture prey, mainly arthropods, to make additional nutrients available for the plant. These pitchers contain a digestive fluid due to the presence of hydrolytic enzymes. In this study, the composition of the digestive fluid was further analysed with regard to mineral nutrients and low molecular-weight compounds. A potential contribution of microbes to the composition of pitcher fluid was investigated.MethodsFluids from closed pitchers were harvested and analysed for mineral nutrients using analytical techniques based on ion-chromatography and inductively coupled plasma-optical emission spectroscopy. Secondary metabolites were identified by a combination of LC-MS and NMR. The presence of bacteria in the pitcher fluid was investigated by PCR of 16S-rRNA genes. Growth analyses of bacteria and yeast were performed in vitro with harvested pitcher fluid and in vivo within pitchers with injected microbes.Key ResultsThe pitcher fluid from closed pitchers was found to be primarily an approx. 25-mm KCl solution, which is free of bacteria and unsuitable for microbial growth probably due to the lack of essential mineral nutrients such as phosphate and inorganic nitrogen. The fluid also contained antimicrobial naphthoquinones, plumbagin and 7-methyl-juglone, and defensive proteins such as the thaumatin-like protein. Challenging with bacteria or yeast caused bactericide as well as fungistatic properties in the fluid. Our results reveal that Nepenthes pitcher fluids represent a dynamic system that is able to react to the presence of microbes.ConclusionsThe secreted liquid of closed and freshly opened Nepenthes pitchers is exclusively plant-derived. It is unsuitable to serve as an environment for microbial growth. Thus, Nepenthes plants can avoid and control, at least to some extent, the microbial colonization of their pitfall traps and, thereby, reduce the need to vie with microbes for the prey-derived nutrients. © The Author 2012. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. Source

Rollin O.,ACTA | Bretagnolle V.,CNRS Chize Center for Biological Studies | Decourtye A.,ACTA | Aptel J.,French National Institute for Agricultural Research | And 5 more authors.
Agriculture, Ecosystems and Environment | Year: 2013

Bees provide an essential pollination service for crops and wild plants. However, substantial declines in bee populations and diversity have been observed in Europe and North America for the past 50 years, partly due to the loss of natural habitats and reduction of plant diversity resulting from agricultural intensification. To mitigate the negative effects of agricultural intensification, agri-environmental schemes (AES) have been proposed to sustain bees and others pollinators in agrosystems. AES include the preservation of semi-natural habitats such as grasslands, fallows, woodlots, hedgerows or set-aside field margins. However, empirical evidence suggest that the use of those semi-natural habitats by bees may vary greatly among bee functional groups and may further be influenced by the presence of alternative foraging habitats such as mass-flowering crops. The present study sets out to investigate whether the three bee groups typically targeted by AES (honey bees, bumble bees and other wild bees) differ in the way they use those semi-natural habitats relative to common mass-flowering crops (oilseed rape, sunflower, alfalfa) in an intensive agricultural farming system. A clear segregation pattern in the use of floral resources appeared between honey bees and wild bees, with the former being tightly associated with mass-flowering crops and the latter with semi-natural habitats. Bumble bees had an intermediate strategy and behaved as habitat generalists. Therefore, it would be sensible to treat the three bee groups with distinct AES management strategies, and to further consider potential effects on AES efficiency of alternative foraging habitats in the surrounding. This study also stresses the importance of native floral resources, particularly in semi-natural herbaceous habitats, for sustaining wild bee populations. © 2013 Elsevier B.V. Source

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