^ 15N isotope tracer techniques and ecological modeling were adopted to investigate the fractionation of nitrogen, its uptake and transformation in algae and snail （Bellamya aeruginosa Reeve）. Different algal specie...^ 15N isotope tracer techniques and ecological modeling were adopted to investigate the fractionation of nitrogen, its uptake and transformation in algae and snail （Bellamya aeruginosa Reeve）. Different algal species were found to differ in their uptake of nitrogen isotopes. Microcystis aeruginisa Ktitz. demonstrated the greatest ^15N accumulation capacity, with the natural variation in isotopic ratio （δ^15N） and the isotope fractionation factor （ε,‰） being the highest among the species investigated. The transformation and utilization of ^15N by snails differed depending on the specific algae consumed （highest for Chlorella pyrenoidosa Chick., lowest for M. aeruginisa）. When snails was seeded in the experimental pond, the algae population structure changed significantly, and total algal biomass as well as the concentration of all nitrogen species decreased, causing an increase in water transparency. A model, incorporating several chemical and biological parameters, was developed to predict algal biomass in an aquatic system when snails was present. The data collected during this investigation indicated that the gastropods such as snails could significantly impact biological community and water quality of small water bodies, suggesting a role for biological control of noxious algal blooms associated with eutrophication.展开更多
Objective: This study was to assess the influence of interaction of combination of immobilized nitrogen cycling bacteria (INCB) with aquatic macrophytes on nitrogen removal from the eutrophic waterbody, and to get ins...Objective: This study was to assess the influence of interaction of combination of immobilized nitrogen cycling bacteria (INCB) with aquatic macrophytes on nitrogen removal from the eutrophic waterbody, and to get insight into different mechanisms involved in nitrogen removal. Methods: The aquatic macrophytes used include Eichhornia crassipes (sum-mer-autumn floating macrophyte), Elodea nuttallii (winter-growing submerged macrophyte), and nitrogen cycling bacteria in-cluding ammonifying, nitrosating, nitrifying and denitrifying bacteria isolated from Taihu Lake. The immobilization carriers materials were made from hydrophilic monomers 2-hydroxyethyl acrylate (HEA) and hydrophobic 2-hydroxyethyl methylacrylate (HEMA). Two experiments were conducted to evaluate the roles of macrophytes combined with INCB on nitrogen removal from eutrophic water during different seasons. Results: Eichhornia crassipes and Elodea nuttallii had different potentials in purification of eutrophic water. Floating macrophyte+bacteria (INCB) performed best in improving water quality (during the first experiment) and decreased total nitrogen (TN) by 70.2%, nitrite and ammonium by 92.2% and 50.9%, respectively, during the experimental period, when water transparency increased from 0.5 m to 1.8 m. When INCB was inoculated into the floating macrophyte system, the populations of nitrosating, nitrifying, and denitrifying bacteria increased by 1 to 2 orders of magnitude compared to the un-inoculated treatments, but ammonifying bacteria showed no obvious difference between different treatments. Lower values of chlorophyll a, CODMn, and pH were found in the microbial-plant integrated system, as compared to the control. Highest reduction in N was noted during the treatment with submerged macrophyte+INCB, being 26.1% for TN, 85.2% for nitrite, and 85.2% for ammonium at the end of 2nd experiment. And in the treatment, the populations of ammonifying, nitrosating, nitrifying, and de-nitrifying bacteria increased by 1 to 3 orders of magnitude, as compared to the un-inoculated treatments. Similar to the first ex-periment, higher water transparency and lower values of chlorophyll a, CODMn and pH were observed in the plant+ INCB inte-grated system, as compared to other treatments. These results indicated that plant-microbe interaction showed beneficial effects on N removal from the eutrophic waterbody.展开更多
White lupin （Lupinus albus） exhibits strong root morphological and physiological responses to phosphorus （P） deficiency and auxin treatments, but the interactive effects of P and auxin in regulating root morpholog...White lupin （Lupinus albus） exhibits strong root morphological and physiological responses to phosphorus （P） deficiency and auxin treatments, but the interactive effects of P and auxin in regulating root morphological and physiological traits are not fully understood. This study aimed to assess white lupin root traits as influenced by P （0 or 250 ~tmol L-1） and auxin （10=8 mol L-1 NAA） in nutrient solution. Both P deficiency and auxin treatments significantly altered root morphological traits, as evi- denced by reduced taproot length, increased number and density of first-order lateral roots, and enhanced cluster-root for- marion. Changes in root physiological traits were also observed, i.e., increased proton, citrate, and acid phosphatase exudation. Exogenous auxin enhanced root responses and sensitivity to P deficiency. A significant interplay exists between P and auxin in the regulation of root morphological and physiological traits. Principal component analysis showed that P availability ex- plained 64.8% and auxin addition 21.3% of the total variation in root trait parameters, indicating that P availability is much more important than auxin in modifying root responses of white lupin. This suggests that white lupin can coordinate root mor- phological and physiological responses to enhance acquisition of P resources, with an optimal trade-off between root morpho- logical and physiological traits regulated by external stimuli such as P availability and auxin.展开更多
基金supported by the National Natural Science Foundation of China (No.30870452)the National Chaohu Lake Special Project of China (No.2008ZX07103-005)
文摘^ 15N isotope tracer techniques and ecological modeling were adopted to investigate the fractionation of nitrogen, its uptake and transformation in algae and snail （Bellamya aeruginosa Reeve）. Different algal species were found to differ in their uptake of nitrogen isotopes. Microcystis aeruginisa Ktitz. demonstrated the greatest ^15N accumulation capacity, with the natural variation in isotopic ratio （δ^15N） and the isotope fractionation factor （ε,‰） being the highest among the species investigated. The transformation and utilization of ^15N by snails differed depending on the specific algae consumed （highest for Chlorella pyrenoidosa Chick., lowest for M. aeruginisa）. When snails was seeded in the experimental pond, the algae population structure changed significantly, and total algal biomass as well as the concentration of all nitrogen species decreased, causing an increase in water transparency. A model, incorporating several chemical and biological parameters, was developed to predict algal biomass in an aquatic system when snails was present. The data collected during this investigation indicated that the gastropods such as snails could significantly impact biological community and water quality of small water bodies, suggesting a role for biological control of noxious algal blooms associated with eutrophication.
基金Project supported by the Ministry of Science and Technology of China, the Education Ministry of China (No. 20305), Australia Gov-ernment’s Innovation Statement Backing Australia’s Ability (No. [2002]68), and the Science and Technology Bureau of ZhejiangProvince (No. 2005C22020), China
文摘Objective: This study was to assess the influence of interaction of combination of immobilized nitrogen cycling bacteria (INCB) with aquatic macrophytes on nitrogen removal from the eutrophic waterbody, and to get insight into different mechanisms involved in nitrogen removal. Methods: The aquatic macrophytes used include Eichhornia crassipes (sum-mer-autumn floating macrophyte), Elodea nuttallii (winter-growing submerged macrophyte), and nitrogen cycling bacteria in-cluding ammonifying, nitrosating, nitrifying and denitrifying bacteria isolated from Taihu Lake. The immobilization carriers materials were made from hydrophilic monomers 2-hydroxyethyl acrylate (HEA) and hydrophobic 2-hydroxyethyl methylacrylate (HEMA). Two experiments were conducted to evaluate the roles of macrophytes combined with INCB on nitrogen removal from eutrophic water during different seasons. Results: Eichhornia crassipes and Elodea nuttallii had different potentials in purification of eutrophic water. Floating macrophyte+bacteria (INCB) performed best in improving water quality (during the first experiment) and decreased total nitrogen (TN) by 70.2%, nitrite and ammonium by 92.2% and 50.9%, respectively, during the experimental period, when water transparency increased from 0.5 m to 1.8 m. When INCB was inoculated into the floating macrophyte system, the populations of nitrosating, nitrifying, and denitrifying bacteria increased by 1 to 2 orders of magnitude compared to the un-inoculated treatments, but ammonifying bacteria showed no obvious difference between different treatments. Lower values of chlorophyll a, CODMn, and pH were found in the microbial-plant integrated system, as compared to the control. Highest reduction in N was noted during the treatment with submerged macrophyte+INCB, being 26.1% for TN, 85.2% for nitrite, and 85.2% for ammonium at the end of 2nd experiment. And in the treatment, the populations of ammonifying, nitrosating, nitrifying, and de-nitrifying bacteria increased by 1 to 3 orders of magnitude, as compared to the un-inoculated treatments. Similar to the first ex-periment, higher water transparency and lower values of chlorophyll a, CODMn and pH were observed in the plant+ INCB inte-grated system, as compared to other treatments. These results indicated that plant-microbe interaction showed beneficial effects on N removal from the eutrophic waterbody.
基金Progress of Projects Supported by NSFCsupported by the National Natural Science Foundation of China (30925024, 30890131, 30871591)+3 种基金the Beijing Natural Science Foundation (6122021)the innovative group grant of NSFC (31121062)Ministry of Science and Technology of China (2013CB127402)the Innovation Fund for Graduate Student of China Agricultural University(KYCX2011040)
文摘White lupin （Lupinus albus） exhibits strong root morphological and physiological responses to phosphorus （P） deficiency and auxin treatments, but the interactive effects of P and auxin in regulating root morphological and physiological traits are not fully understood. This study aimed to assess white lupin root traits as influenced by P （0 or 250 ~tmol L-1） and auxin （10=8 mol L-1 NAA） in nutrient solution. Both P deficiency and auxin treatments significantly altered root morphological traits, as evi- denced by reduced taproot length, increased number and density of first-order lateral roots, and enhanced cluster-root for- marion. Changes in root physiological traits were also observed, i.e., increased proton, citrate, and acid phosphatase exudation. Exogenous auxin enhanced root responses and sensitivity to P deficiency. A significant interplay exists between P and auxin in the regulation of root morphological and physiological traits. Principal component analysis showed that P availability ex- plained 64.8% and auxin addition 21.3% of the total variation in root trait parameters, indicating that P availability is much more important than auxin in modifying root responses of white lupin. This suggests that white lupin can coordinate root mor- phological and physiological responses to enhance acquisition of P resources, with an optimal trade-off between root morpho- logical and physiological traits regulated by external stimuli such as P availability and auxin.
