Gervais Rufyikiri - Academia.edu (original) (raw)

Papers by Gervais Rufyikiri

Research paper thumbnail of Contraintes nutritionnelles chez le bananier (Musa spp.) cultivé en milieux riches en aluminium soluble et conséquences sur sa croissance

(AGRO - Sciences agronomiques et ingénierie biologique) -- UCL, 200

Research paper thumbnail of African Union-Led Peacekeeping Operations: Constraints and Opportunities of Interagency Cooperation in the Experience of Burundi and South Africa

Information & Security: An International Journal

Research paper thumbnail of NaCl and Na2SO4 Salinities Have Different Impact on Photosynthesis and Yield-Related Parameters in Rice (Oryza sativa L.)

Agronomy

To elucidate the comparative effect of chloride and sulfate salinities on photosynthesis and yiel... more To elucidate the comparative effect of chloride and sulfate salinities on photosynthesis and yield components in rice, plants of Oryza sativa (cv. I Kong Pao (salt-sensitive)) were exposed in nutrient solutions to 20 mM Na2SO4 or 40 mM NaCl (electrical conductivity of c.a. 4.30 dS m−1 for both solutions) from seedlings to maturity stage. Both types of salt induced a strong decrease in net photosynthesis (AN) at the seedling and tillering stages, while the intercellular CO2 concentrations (Ci) remained unaffected. Instantaneous transpiration (E) and stomatal conductance (gs) decreased at the tillering and seedling stages, respectively, only in plants exposed to NaCl. Chloride salinity also strongly decreased photosynthetic pigments, while no impact was detected in response to Na2SO4. All yield-related parameters were affected by salinities, but NaCl was significantly more deleterious than Na2SO4 for the mean number of tillers produced per plant, spikelets sterility and non-viable pol...

Research paper thumbnail of Daily rainfall above 75mm is a major trigger to landslides in the Muhunguzi, western Burundi

<p>... more <p>Located in the East African Rift Valley, western Burundi is often threatened by landslides during the rainy season. Damage can be seen both in the mountains, the sites of the landslides, and in the plain where sediments are deposited: environmental degradation, loss upstream and downstream of cultivated land, destruction of infrastructures, loss of life, waterborne diseases, floods of streams laden with sludge and stones torn off during landslides... The magnitude of these shifts justifies the need for studies to understand the factors that cause this part of Burundi to be vulnerable to landslides.</p><p>Here we highlight the relationship between the environmental context and the process of landslides in this region. To analyze the impact of geomorphological, geological, soil and climatic conditions as well as anthropogenic factors, we carried out an inventory of landslides in the Muhunguzi watershed, a survey of the local population and an analysis of rainfall over the period 1935-2014.</p><p>Of 7 Muhunguzi sub-watersheds with a total area of 21.2 km<sup>2</sup>, 43 landslides were identified, 29 of which were on a single sub-watershed. Most landslides were shallow. Geomorphology was characterized by steep escarpments interspersed with valleys. The landslides were located on the lower slopes and most affected the rivers. The lithology was dominated by shale inclined parallel to the slope. Landslides were located on rocky, black or red soils, identified as Nitisols. The majority of landslides occurred on cultivated fields. Daily precipitations ranging between 75mm and 100mm with a return period of 5.3 years are strongly correlated to shallow landslides in the studied area. Such intense daily rain thus appears here as a major trigger to these landslides. In addition, relief, geological and soil conditions are predisposing factors while population density and the resulting land pressure worsen land instability.</p><p>We conclude that further studies are needed to understand the impact of soil processes and human activity in order to identify adequate management practices preventing landslides in Muhunguzi area.</p>

Research paper thumbnail of The Post-wartime Trajectory of CNDD-FDD Party in Burundi: A Facade Transformation of Rebel Movement to Political Party

Research paper thumbnail of Comparative effects of chloride and sulfate salinities on two contrasting rice cultivars (Oryza sativa L.) at the seedling stage

Journal of Plant Nutrition

Research paper thumbnail of Role of arbuscular mycorrhizal fungi in the uptake of phosphorus by micropropagated blackberry (Rubus fruticosus var. brazos) plants

Developments in Plant and Soil Sciences, 2007

... Y. Carreo´n-Abud1,3, E. Soriano-Bello2 & M. Martı´nez-Trujillo1 1Laboratorio de Microbiol... more ... Y. Carreo´n-Abud1,3, E. Soriano-Bello2 & M. Martı´nez-Trujillo1 1Laboratorio de Microbiologıá, Facultad de Biologıá, Universidad Michoacana de San ... To MC Lourdes Ballesteros Almanza, for her contribution in the experiments and to Miss Yasmı´n Martı´nez Car-reo´n for ...

Research paper thumbnail of Cation Exchange on Plant Roots Involving Aluminium

Trace Elements in the Rhizosphere, 2000

... Experimental Data and Modeling Joseph E. Dufey, Jose G. Genon, Benoft Jaillard, Henri Calba, ... more ... Experimental Data and Modeling Joseph E. Dufey, Jose G. Genon, Benoft Jaillard, Henri Calba, Gervais Rufyikiri, and Bruno Delvaux CONTENTS ... ion distribution in this surface-unbound phase (or Donnan free space) is regulated according to the Maxwell-Boltzmann equation. ...

Research paper thumbnail of Uptake and translocation of uranium by arbuscular mycorrhizal fungi under monoxenic culture conditions

Biogeochemistry of Trace Elements in the Rhizosphere, 2005

ABSTRACT Fundamental information on the transport of uranium by mycelium of arbuscular mycorrhiza... more ABSTRACT Fundamental information on the transport of uranium by mycelium of arbuscular mycorrhizal (AM) fungi is reported and discussed in this chapter. The monoxenic cultivation system was shown to be convenient to investigate the processes of uptake and translocation of uranium by AM fungi, as it was already reported for some other elements. The evidence that extraradical AM hyphae can take up U and translocate it towards the host roots was clearly shown. Further research to understand the mechanisms involved and future prospects were also suggested.

Research paper thumbnail of Effects of arbuscular mycorrhizal fungi on severity of root rot of bananas caused by Cylindrocladium spathiphylli

Plant Pathology, 2002

The interaction between four arbuscular mycorrhizal (AM) fungi, Glomus sp., G. proliferum , G. in... more The interaction between four arbuscular mycorrhizal (AM) fungi, Glomus sp., G. proliferum , G. intraradices and G. versiforme , and the root-rot fungus Cylindrocladium spathiphylli , and subsequent effects on growth and phosphorus nutrition of banana (Musa acuminata , AAA, cv. Grande Naine) were investigated under glasshouse conditions. Overall, root infection by C. spathiphylli reduced the growth of banana plants, but preinoculation with AM fungi significantly attenuated this detrimental effect. Lower disease severity, stimulation of growth and increase of shoot P content were observed for the plants inoculated with one of the four AM fungi. Glomus sp. and G. proliferum induced the largest increase in growth parameters and shoot P content as compared to G. intraradices and G. versiforme , in the presence as well as in the absence of C. spathiphylli. Root damage caused by C. spathiphylli was decreased in the presence of AM fungi, but the inoculation of mycorrhizal plants with C. spathiphylli also decreased the intensity of AM fungal root colonization, indicating a clear interaction between the two organisms.

Research paper thumbnail of Arbuscular mycorrhizal fungi might alleviate aluminium toxicity in banana plants

New Phytologist, 2000

ABSTRACT

Research paper thumbnail of Contribution of hyphae and roots to uranium uptake and translocation by arbuscular mycorrhizal carrot roots under root-organ culture conditions

New Phytologist, 2003

• Here, the respective contributions of the arbuscular mycorrhizal (AM) fungus Glomus intraradice... more • Here, the respective contributions of the arbuscular mycorrhizal (AM) fungus Glomus intraradices and carrot (Daucus carota) roots to the uptake and translocation of uranium (U) were quantified and compared. • The U absorption by the AM fungus and roots was observed by growing mycorrhizal and nonmycorrhizal roots in two-compartment Petri plates. The central compartment allowed growth of roots and extraradical fungal hyphae. The external compartment (EC), which was labelled with 0.1 µ M 233 U, allowed growth of: hyphae only (hyphal compartment, HC), both mycorrhizal roots and hyphae (root hyphal compartment, RHC), or nonmycorrhizal roots (root compartment, RC). • The U concentration was 5.5 and 9.6 times higher for hyphae than for the mycorrhizal and nonmycorrhizal roots, respectively, both developing in the EC's. Translocation of U was similar for the RHC and the HC systems, and was 8 times higher for these two systems than for the RC system. • These results indicate that the U flux rate was higher in fungal hyphae than in roots, while the intraradical hyphae may significantly contribute to the U immobilization by mycorrhizal roots.

Research paper thumbnail of Uranium uptake and translocation by the arbuscular mycorrhizal fungus, Glomus intraradices, under root-organ culture conditions

New Phytologist, 2002

• Uranium (U) uptake and translocation by the arbuscular mycorrhizal (AM) fungus Glomus intraradi... more • Uranium (U) uptake and translocation by the arbuscular mycorrhizal (AM) fungus Glomus intraradices were studied under root-organ culture conditions with Agrobacterium rhizogenes-transformed carrot (Daucus carota) roots as host. • Two-compartment Petri plates were used to spatially separate a root compartment (RC) and a hyphal compartment (HC); root growth was restricted to the RC while extraradical hyphae grew in both RC and HC. The HC was labelled with 0.1 µM 233 U at different pH conditions. At the end of the experiment, U was measured in the RC and in the HC. • The U absorption by the AM fungus was observed. It included; U uptake by the mycelium developing in the HC, and U translocation from the HC to the RC. The magnitude of this uptake and translocation was highly influenced by the pH of the growth medium, while translocation was highly correlated with the number of hyphae crossing the partition separating the two compartments. • These results are the first to show that an AM fungus can take up and translocate U towards roots.

Research paper thumbnail of Comparison of 233U and 33P uptake and translocation by the arbuscular mycorrhizal fungus Glomus intraradices in root organ culture conditions

Mycorrhiza, 2004

This study aimed to quantify and compare 233U and 33P uptake and translocation by hyphae of the a... more This study aimed to quantify and compare 233U and 33P uptake and translocation by hyphae of the arbuscular mycorrhizal (AM) fungus Glomus intraradices in root organ culture conditions with transformed carrot (Daucus carota L.) roots as host. Mycorrhizal roots were grown in two-compartment Petri dishes to spatially separate a root compartment (RC) and a hyphal compartment (HC). The HC was labelled with 8.33 Bq 233U ml(-1) and 13.33 Bq 33P ml(-1). After 2 weeks contact between hyphae and the labelled solution, 233U and 33P activities were measured in the RC and in the HC. 233U and 33P were taken up by the extraradical AM mycelium grown in the HC and this uptake represented 4.4% and 16% of the initial isotope supply, respectively. The translocation into roots developing in the RC via hyphae accounted for 5.9% and 72% of the initial isotope supply, respectively. Thus, both uptake and translocation were much higher for 33P than for 233U. This suggests (1) the existence in hyphal tissues of efficient mechanisms limiting the uptake and translocation of non-essential elements such as U, and (2) that the hyphae have a higher sequestration than translocation function for U, and the converse for P.

Research paper thumbnail of Competitive Adsorption of Hydrogen, Calcium, Potassium, Magnesium, and Aluminum on Banana Roots: Experimental Data and Modeling

Journal of Plant Nutrition, 2003

Aluminum (Al) adsorption on root exchange sites is one of the mechanisms that can be responsible ... more Aluminum (Al) adsorption on root exchange sites is one of the mechanisms that can be responsible for Al toxicity. Experimental measurements of calcium (Ca), magnesium (Mg), potassium (K), and Al adsorption on the main root axes of 5 banana cultivars (Grande Naine, Agbagba, Obino l'Ewaï, Kayinja, and Igitsiri) were carried out at pH 3.75 and 4.25. The data obtained were

Research paper thumbnail of Impact of arbuscular mycorrhizal fungi on uranium accumulation by plants

Journal of Environmental Radioactivity, 2008

Contamination by uranium (U) occurs principally at U mining and processing sites. Uranium can hav... more Contamination by uranium (U) occurs principally at U mining and processing sites. Uranium can have tremendous environmental consequences, as it is highly toxic to a broad range of organisms and can be dispersed in both terrestrial and aquatic environments. Remediation strategies of U-contaminated soils have included physical and chemical procedures, which may be beneficial, but are costly and can lead to further environmental damage. Phytoremediation has been proposed as a promising alternative, which relies on the capacity of plants and their associated microorganisms to stabilize or extract contaminants from soils. In this paper, we review the role of a group of plant symbiotic fungi, i.e. arbuscular mycorrhizal fungi, which constitute an essential link between the soil and the roots. These fungi participate in U immobilization in soils and within plant roots and they can reduce root-to-shoot translocation of U. However, there is a need to evaluate these observations in terms of their importance for phytostabilization strategies.

Research paper thumbnail of Role and influence of mycorrhizal fungi on radiocesium accumulation by plants

Journal of Environmental Radioactivity, 2008

This review summarizes current knowledge on the contribution of mycorrhizal fungi to radiocesium ... more This review summarizes current knowledge on the contribution of mycorrhizal fungi to radiocesium immobilization and plant accumulation. These root symbionts develop extended hyphae in soils and readily contribute to the soil-to-plant transfer of some nutrients. Available data show that ecto-mycorrhizal (ECM) fungi can accumulate high concentration of radiocesium in their extraradical phase while radiocesium uptake and accumulation by arbuscular mycorrhizal (AM) fungi is limited. Yet, both ECM and AM fungi can transport radiocesium to their host plants, but this transport is low. In addition, mycorrhizal fungi could thus either store radiocesium in their intraradical phase or limit its root-to-shoot translocation. The review discusses the impact of soil characteristics, and fungal and plant transporters on radiocesium uptake and accumulation in plants, as well as the potential role of mycorrhizal fungi in phytoremediation strategies.

Research paper thumbnail of Uranium distribution and cycling in Scots pine (Pinus sylvestris L.) growing on a revegetated U-mining heap

Journal of Environmental Radioactivity, 2005

We determined the uranium distribution in soil and its allocation in compartments of 35year-old S... more We determined the uranium distribution in soil and its allocation in compartments of 35year-old Scots pine developed on a revegetated U-mining heap. The processes controlling the dynamics of U recycling were identified and further quantified in terms of annual fluxes. As pine developed, an acid humus layer emerged leading to weathering of the alkaline mining debris but this had little effect on U mobility in the soil profile. Increased U mobility mainly involved a translocation of U to metal-humus chelates in surface layers. The root compartment accounted for 99.3% of the U budget in tree, thus serving as an effective barrier which restricts U uptake. The current root uptake and transfer of U to upper parts of the tree amounted to about 3 g ha ÿ1 y ÿ1 , i.e. less than 0.03% of the current NH 4-exchangeable U pool in the soil (0e30 cm). Allocation and translocation pattern made it clear that a dominant fraction of the translocated U moves passively with the ascent xylem sap, most likely as a soluble complex, and steadily accumulates in the needles. Consequently, 97% of the

Research paper thumbnail of Effect of aluminium on bananas ( Musa spp.) cultivated in acid solutions. II. Water and nutrient uptake

Fruits, 2001

Effect of aluminium on bananas (Musa spp.) cultivated in acid solutions. II. Water and nutrient u... more Effect of aluminium on bananas (Musa spp.) cultivated in acid solutions. II. Water and nutrient uptake.

Research paper thumbnail of Effects of phosphorus fertilization on the availability and uptake of uranium and nutrients by plants grown on soil derived from uranium mining debris

Environmental Pollution, 2006

Subterranean clover and barley were grown on a soil derived from uranium mining debris and fertil... more Subterranean clover and barley were grown on a soil derived from uranium mining debris and fertilized with phosphate as a U immobilizing additive for in situ remediation. We investigated the beneficial effect of P fertilization in the range 0e500 mg P kg ÿ1 soil in terms of U extractability, plant biomass production and U uptake. Increasing P in the mining debris caused a significant decrease of the water-soluble U and NH 4-Ac extractable U at pH 7 and 5. For both plant species, P fertilization considerably increased root and shoot dry matter up to a maximum observed for soil receiving 100 mg P kg ÿ1 while the soil-to-plant transfer of U was regularly decreased by increasing P content in soil. These observations show that P fertilization represents an in situ practical option to facilitate the revegetation of U-mining heaps and to reduce the risks of biota exposure to U contamination.

Research paper thumbnail of Contraintes nutritionnelles chez le bananier (Musa spp.) cultivé en milieux riches en aluminium soluble et conséquences sur sa croissance

(AGRO - Sciences agronomiques et ingénierie biologique) -- UCL, 200

Research paper thumbnail of African Union-Led Peacekeeping Operations: Constraints and Opportunities of Interagency Cooperation in the Experience of Burundi and South Africa

Information & Security: An International Journal

Research paper thumbnail of NaCl and Na2SO4 Salinities Have Different Impact on Photosynthesis and Yield-Related Parameters in Rice (Oryza sativa L.)

Agronomy

To elucidate the comparative effect of chloride and sulfate salinities on photosynthesis and yiel... more To elucidate the comparative effect of chloride and sulfate salinities on photosynthesis and yield components in rice, plants of Oryza sativa (cv. I Kong Pao (salt-sensitive)) were exposed in nutrient solutions to 20 mM Na2SO4 or 40 mM NaCl (electrical conductivity of c.a. 4.30 dS m−1 for both solutions) from seedlings to maturity stage. Both types of salt induced a strong decrease in net photosynthesis (AN) at the seedling and tillering stages, while the intercellular CO2 concentrations (Ci) remained unaffected. Instantaneous transpiration (E) and stomatal conductance (gs) decreased at the tillering and seedling stages, respectively, only in plants exposed to NaCl. Chloride salinity also strongly decreased photosynthetic pigments, while no impact was detected in response to Na2SO4. All yield-related parameters were affected by salinities, but NaCl was significantly more deleterious than Na2SO4 for the mean number of tillers produced per plant, spikelets sterility and non-viable pol...

Research paper thumbnail of Daily rainfall above 75mm is a major trigger to landslides in the Muhunguzi, western Burundi

<p>... more <p>Located in the East African Rift Valley, western Burundi is often threatened by landslides during the rainy season. Damage can be seen both in the mountains, the sites of the landslides, and in the plain where sediments are deposited: environmental degradation, loss upstream and downstream of cultivated land, destruction of infrastructures, loss of life, waterborne diseases, floods of streams laden with sludge and stones torn off during landslides... The magnitude of these shifts justifies the need for studies to understand the factors that cause this part of Burundi to be vulnerable to landslides.</p><p>Here we highlight the relationship between the environmental context and the process of landslides in this region. To analyze the impact of geomorphological, geological, soil and climatic conditions as well as anthropogenic factors, we carried out an inventory of landslides in the Muhunguzi watershed, a survey of the local population and an analysis of rainfall over the period 1935-2014.</p><p>Of 7 Muhunguzi sub-watersheds with a total area of 21.2 km<sup>2</sup>, 43 landslides were identified, 29 of which were on a single sub-watershed. Most landslides were shallow. Geomorphology was characterized by steep escarpments interspersed with valleys. The landslides were located on the lower slopes and most affected the rivers. The lithology was dominated by shale inclined parallel to the slope. Landslides were located on rocky, black or red soils, identified as Nitisols. The majority of landslides occurred on cultivated fields. Daily precipitations ranging between 75mm and 100mm with a return period of 5.3 years are strongly correlated to shallow landslides in the studied area. Such intense daily rain thus appears here as a major trigger to these landslides. In addition, relief, geological and soil conditions are predisposing factors while population density and the resulting land pressure worsen land instability.</p><p>We conclude that further studies are needed to understand the impact of soil processes and human activity in order to identify adequate management practices preventing landslides in Muhunguzi area.</p>

Research paper thumbnail of The Post-wartime Trajectory of CNDD-FDD Party in Burundi: A Facade Transformation of Rebel Movement to Political Party

Research paper thumbnail of Comparative effects of chloride and sulfate salinities on two contrasting rice cultivars (Oryza sativa L.) at the seedling stage

Journal of Plant Nutrition

Research paper thumbnail of Role of arbuscular mycorrhizal fungi in the uptake of phosphorus by micropropagated blackberry (Rubus fruticosus var. brazos) plants

Developments in Plant and Soil Sciences, 2007

... Y. Carreo´n-Abud1,3, E. Soriano-Bello2 & M. Martı´nez-Trujillo1 1Laboratorio de Microbiol... more ... Y. Carreo´n-Abud1,3, E. Soriano-Bello2 & M. Martı´nez-Trujillo1 1Laboratorio de Microbiologıá, Facultad de Biologıá, Universidad Michoacana de San ... To MC Lourdes Ballesteros Almanza, for her contribution in the experiments and to Miss Yasmı´n Martı´nez Car-reo´n for ...

Research paper thumbnail of Cation Exchange on Plant Roots Involving Aluminium

Trace Elements in the Rhizosphere, 2000

... Experimental Data and Modeling Joseph E. Dufey, Jose G. Genon, Benoft Jaillard, Henri Calba, ... more ... Experimental Data and Modeling Joseph E. Dufey, Jose G. Genon, Benoft Jaillard, Henri Calba, Gervais Rufyikiri, and Bruno Delvaux CONTENTS ... ion distribution in this surface-unbound phase (or Donnan free space) is regulated according to the Maxwell-Boltzmann equation. ...

Research paper thumbnail of Uptake and translocation of uranium by arbuscular mycorrhizal fungi under monoxenic culture conditions

Biogeochemistry of Trace Elements in the Rhizosphere, 2005

ABSTRACT Fundamental information on the transport of uranium by mycelium of arbuscular mycorrhiza... more ABSTRACT Fundamental information on the transport of uranium by mycelium of arbuscular mycorrhizal (AM) fungi is reported and discussed in this chapter. The monoxenic cultivation system was shown to be convenient to investigate the processes of uptake and translocation of uranium by AM fungi, as it was already reported for some other elements. The evidence that extraradical AM hyphae can take up U and translocate it towards the host roots was clearly shown. Further research to understand the mechanisms involved and future prospects were also suggested.

Research paper thumbnail of Effects of arbuscular mycorrhizal fungi on severity of root rot of bananas caused by Cylindrocladium spathiphylli

Plant Pathology, 2002

The interaction between four arbuscular mycorrhizal (AM) fungi, Glomus sp., G. proliferum , G. in... more The interaction between four arbuscular mycorrhizal (AM) fungi, Glomus sp., G. proliferum , G. intraradices and G. versiforme , and the root-rot fungus Cylindrocladium spathiphylli , and subsequent effects on growth and phosphorus nutrition of banana (Musa acuminata , AAA, cv. Grande Naine) were investigated under glasshouse conditions. Overall, root infection by C. spathiphylli reduced the growth of banana plants, but preinoculation with AM fungi significantly attenuated this detrimental effect. Lower disease severity, stimulation of growth and increase of shoot P content were observed for the plants inoculated with one of the four AM fungi. Glomus sp. and G. proliferum induced the largest increase in growth parameters and shoot P content as compared to G. intraradices and G. versiforme , in the presence as well as in the absence of C. spathiphylli. Root damage caused by C. spathiphylli was decreased in the presence of AM fungi, but the inoculation of mycorrhizal plants with C. spathiphylli also decreased the intensity of AM fungal root colonization, indicating a clear interaction between the two organisms.

Research paper thumbnail of Arbuscular mycorrhizal fungi might alleviate aluminium toxicity in banana plants

New Phytologist, 2000

ABSTRACT

Research paper thumbnail of Contribution of hyphae and roots to uranium uptake and translocation by arbuscular mycorrhizal carrot roots under root-organ culture conditions

New Phytologist, 2003

• Here, the respective contributions of the arbuscular mycorrhizal (AM) fungus Glomus intraradice... more • Here, the respective contributions of the arbuscular mycorrhizal (AM) fungus Glomus intraradices and carrot (Daucus carota) roots to the uptake and translocation of uranium (U) were quantified and compared. • The U absorption by the AM fungus and roots was observed by growing mycorrhizal and nonmycorrhizal roots in two-compartment Petri plates. The central compartment allowed growth of roots and extraradical fungal hyphae. The external compartment (EC), which was labelled with 0.1 µ M 233 U, allowed growth of: hyphae only (hyphal compartment, HC), both mycorrhizal roots and hyphae (root hyphal compartment, RHC), or nonmycorrhizal roots (root compartment, RC). • The U concentration was 5.5 and 9.6 times higher for hyphae than for the mycorrhizal and nonmycorrhizal roots, respectively, both developing in the EC's. Translocation of U was similar for the RHC and the HC systems, and was 8 times higher for these two systems than for the RC system. • These results indicate that the U flux rate was higher in fungal hyphae than in roots, while the intraradical hyphae may significantly contribute to the U immobilization by mycorrhizal roots.

Research paper thumbnail of Uranium uptake and translocation by the arbuscular mycorrhizal fungus, Glomus intraradices, under root-organ culture conditions

New Phytologist, 2002

• Uranium (U) uptake and translocation by the arbuscular mycorrhizal (AM) fungus Glomus intraradi... more • Uranium (U) uptake and translocation by the arbuscular mycorrhizal (AM) fungus Glomus intraradices were studied under root-organ culture conditions with Agrobacterium rhizogenes-transformed carrot (Daucus carota) roots as host. • Two-compartment Petri plates were used to spatially separate a root compartment (RC) and a hyphal compartment (HC); root growth was restricted to the RC while extraradical hyphae grew in both RC and HC. The HC was labelled with 0.1 µM 233 U at different pH conditions. At the end of the experiment, U was measured in the RC and in the HC. • The U absorption by the AM fungus was observed. It included; U uptake by the mycelium developing in the HC, and U translocation from the HC to the RC. The magnitude of this uptake and translocation was highly influenced by the pH of the growth medium, while translocation was highly correlated with the number of hyphae crossing the partition separating the two compartments. • These results are the first to show that an AM fungus can take up and translocate U towards roots.

Research paper thumbnail of Comparison of 233U and 33P uptake and translocation by the arbuscular mycorrhizal fungus Glomus intraradices in root organ culture conditions

Mycorrhiza, 2004

This study aimed to quantify and compare 233U and 33P uptake and translocation by hyphae of the a... more This study aimed to quantify and compare 233U and 33P uptake and translocation by hyphae of the arbuscular mycorrhizal (AM) fungus Glomus intraradices in root organ culture conditions with transformed carrot (Daucus carota L.) roots as host. Mycorrhizal roots were grown in two-compartment Petri dishes to spatially separate a root compartment (RC) and a hyphal compartment (HC). The HC was labelled with 8.33 Bq 233U ml(-1) and 13.33 Bq 33P ml(-1). After 2 weeks contact between hyphae and the labelled solution, 233U and 33P activities were measured in the RC and in the HC. 233U and 33P were taken up by the extraradical AM mycelium grown in the HC and this uptake represented 4.4% and 16% of the initial isotope supply, respectively. The translocation into roots developing in the RC via hyphae accounted for 5.9% and 72% of the initial isotope supply, respectively. Thus, both uptake and translocation were much higher for 33P than for 233U. This suggests (1) the existence in hyphal tissues of efficient mechanisms limiting the uptake and translocation of non-essential elements such as U, and (2) that the hyphae have a higher sequestration than translocation function for U, and the converse for P.

Research paper thumbnail of Competitive Adsorption of Hydrogen, Calcium, Potassium, Magnesium, and Aluminum on Banana Roots: Experimental Data and Modeling

Journal of Plant Nutrition, 2003

Aluminum (Al) adsorption on root exchange sites is one of the mechanisms that can be responsible ... more Aluminum (Al) adsorption on root exchange sites is one of the mechanisms that can be responsible for Al toxicity. Experimental measurements of calcium (Ca), magnesium (Mg), potassium (K), and Al adsorption on the main root axes of 5 banana cultivars (Grande Naine, Agbagba, Obino l'Ewaï, Kayinja, and Igitsiri) were carried out at pH 3.75 and 4.25. The data obtained were

Research paper thumbnail of Impact of arbuscular mycorrhizal fungi on uranium accumulation by plants

Journal of Environmental Radioactivity, 2008

Contamination by uranium (U) occurs principally at U mining and processing sites. Uranium can hav... more Contamination by uranium (U) occurs principally at U mining and processing sites. Uranium can have tremendous environmental consequences, as it is highly toxic to a broad range of organisms and can be dispersed in both terrestrial and aquatic environments. Remediation strategies of U-contaminated soils have included physical and chemical procedures, which may be beneficial, but are costly and can lead to further environmental damage. Phytoremediation has been proposed as a promising alternative, which relies on the capacity of plants and their associated microorganisms to stabilize or extract contaminants from soils. In this paper, we review the role of a group of plant symbiotic fungi, i.e. arbuscular mycorrhizal fungi, which constitute an essential link between the soil and the roots. These fungi participate in U immobilization in soils and within plant roots and they can reduce root-to-shoot translocation of U. However, there is a need to evaluate these observations in terms of their importance for phytostabilization strategies.

Research paper thumbnail of Role and influence of mycorrhizal fungi on radiocesium accumulation by plants

Journal of Environmental Radioactivity, 2008

This review summarizes current knowledge on the contribution of mycorrhizal fungi to radiocesium ... more This review summarizes current knowledge on the contribution of mycorrhizal fungi to radiocesium immobilization and plant accumulation. These root symbionts develop extended hyphae in soils and readily contribute to the soil-to-plant transfer of some nutrients. Available data show that ecto-mycorrhizal (ECM) fungi can accumulate high concentration of radiocesium in their extraradical phase while radiocesium uptake and accumulation by arbuscular mycorrhizal (AM) fungi is limited. Yet, both ECM and AM fungi can transport radiocesium to their host plants, but this transport is low. In addition, mycorrhizal fungi could thus either store radiocesium in their intraradical phase or limit its root-to-shoot translocation. The review discusses the impact of soil characteristics, and fungal and plant transporters on radiocesium uptake and accumulation in plants, as well as the potential role of mycorrhizal fungi in phytoremediation strategies.

Research paper thumbnail of Uranium distribution and cycling in Scots pine (Pinus sylvestris L.) growing on a revegetated U-mining heap

Journal of Environmental Radioactivity, 2005

We determined the uranium distribution in soil and its allocation in compartments of 35year-old S... more We determined the uranium distribution in soil and its allocation in compartments of 35year-old Scots pine developed on a revegetated U-mining heap. The processes controlling the dynamics of U recycling were identified and further quantified in terms of annual fluxes. As pine developed, an acid humus layer emerged leading to weathering of the alkaline mining debris but this had little effect on U mobility in the soil profile. Increased U mobility mainly involved a translocation of U to metal-humus chelates in surface layers. The root compartment accounted for 99.3% of the U budget in tree, thus serving as an effective barrier which restricts U uptake. The current root uptake and transfer of U to upper parts of the tree amounted to about 3 g ha ÿ1 y ÿ1 , i.e. less than 0.03% of the current NH 4-exchangeable U pool in the soil (0e30 cm). Allocation and translocation pattern made it clear that a dominant fraction of the translocated U moves passively with the ascent xylem sap, most likely as a soluble complex, and steadily accumulates in the needles. Consequently, 97% of the

Research paper thumbnail of Effect of aluminium on bananas ( Musa spp.) cultivated in acid solutions. II. Water and nutrient uptake

Fruits, 2001

Effect of aluminium on bananas (Musa spp.) cultivated in acid solutions. II. Water and nutrient u... more Effect of aluminium on bananas (Musa spp.) cultivated in acid solutions. II. Water and nutrient uptake.

Research paper thumbnail of Effects of phosphorus fertilization on the availability and uptake of uranium and nutrients by plants grown on soil derived from uranium mining debris

Environmental Pollution, 2006

Subterranean clover and barley were grown on a soil derived from uranium mining debris and fertil... more Subterranean clover and barley were grown on a soil derived from uranium mining debris and fertilized with phosphate as a U immobilizing additive for in situ remediation. We investigated the beneficial effect of P fertilization in the range 0e500 mg P kg ÿ1 soil in terms of U extractability, plant biomass production and U uptake. Increasing P in the mining debris caused a significant decrease of the water-soluble U and NH 4-Ac extractable U at pH 7 and 5. For both plant species, P fertilization considerably increased root and shoot dry matter up to a maximum observed for soil receiving 100 mg P kg ÿ1 while the soil-to-plant transfer of U was regularly decreased by increasing P content in soil. These observations show that P fertilization represents an in situ practical option to facilitate the revegetation of U-mining heaps and to reduce the risks of biota exposure to U contamination.