The basic leucine zipper(bZIP)transcription factor HY5 plays a multifaceted role in plant growth and development.Here the apple MdHY5 gene was cloned based on its homology with Arabidopsis HY5.Expression analysis demo...The basic leucine zipper(bZIP)transcription factor HY5 plays a multifaceted role in plant growth and development.Here the apple MdHY5 gene was cloned based on its homology with Arabidopsis HY5.Expression analysis demonstrated that MdHY5 transcription was induced by light and abscisic acid treatments.Electrophoretic mobility shift assays and transient expression assays subsequently showed that MdHY5 positively regulated both its own transcription and that of MdMYB10 by binding to E-box and G-box motifs,respectively.Furthermore,we obtained transgenic apple calli that overexpressed the MdHY5 gene,and apple calli coloration assays showed that MdHY5 promoted anthocyanin accumulation by regulating expression of the MdMYB10 gene and downstream anthocyanin biosynthesis genes.In addition,the transcript levels of a series of nitrate reductase genes and nitrate uptake genes in both wild-type and transgenic apple calli were detected.In association with increased nitrate reductase activities and nitrate contents,the results indicated that MdHY5 might be an important regulator in nutrient assimilation.Taken together,these results indicate that MdHY5 plays a vital role in anthocyanin accumulation and nitrate assimilation in apple.展开更多
Nitrogen(N)is the driving force for crop yields;however,excessive N application in agriculture not only increases production cost,but also causes severe environmental problems.Therefore,comprehensively understanding t...Nitrogen(N)is the driving force for crop yields;however,excessive N application in agriculture not only increases production cost,but also causes severe environmental problems.Therefore,comprehensively understanding the molecular mechanisms of N use efficiency(NUE)and breeding crops with higher NUE is essential to tackle these problems.NUE of crops is determined by N uptake,transport,assimilation,and remobilization.In the process of N assimilation,nitrate reductase(NR),nitrite reductase(Ni R),glutamine synthetase(GS),and glutamine-2-oxoglutarate aminotransferase(GOGAT,also known as glutamate synthase)are the major enzymes.NR and Ni R mediate the initiation of inorganic N utilization,and GS/GOGAT cycle converts inorganic N to organic N,playing a vital role in N assimilation and the final NUE of crops.Besides,asparagine synthetase(ASN),glutamate dehydrogenase(GDH),and carbamoyl phosphate synthetase(CPSase)are also involved.In this review,we summarize the function and regulation of these enzymes reported in three major crops—rice,maize,and wheat,also in the model plant Arabidopsis,and we highlight their application in improving NUE of crops via manipulating N assimilation.Anticipated challenges and prospects toward fully understanding the function of N assimilation and further exploring the potential for NUE improvement are discussed.展开更多
Effects of water stress and foliar boron (FB) application on soybean (Glycine max (L) Merr.) seed composition and nitrogen metabolism have not been well investigated. Therefore, the objective of this study was to inve...Effects of water stress and foliar boron (FB) application on soybean (Glycine max (L) Merr.) seed composition and nitrogen metabolism have not been well investigated. Therefore, the objective of this study was to investigate the effects of water stress and FB on seed protein, oil, fatty acids, nitrate reductase activity (NRA), and nitrogenase activity (NA). A repeated greenhouse experiment was conducted where one set of soybean plants were subjected to water stress (WS), and the other set was watered (W). Foliar boron (B) was applied at rate of 0.45 kg·ha-1. Treatments were watered-plants with no FB (W), watered-plants with FB (WB), water-stress plants with no FB (WS), and water-stress plants with FB (WSB). The results showed that seed protein and oil percentage were significantly (P 15N/ 14N and 13C/12C natural abundance were altered between watered-and watered-stressed plants. These results suggest that water stress and FB can influence seed composition, and nitrogen metabolism, and 15N/14N and 13C/12C ratios, reflecting environmental and metabolic changes in carbon and nitrogen fixation pathways. Lack of B translocation from leaves to seed under water stress may suggest a possible mechanism of limited B translocation under water stress. These findings may be beneficial to breeders to select for B translocation efficiency under drought conditions. Altered 15N/14N and 13C/12C under water stress can be used as a tool to select for drought tolerance using N and C isotopes in the breeding programs.展开更多
In this paper, the role of mixed amino acids in nitrate uptake and assimilation was evaluated in leafy radish by using ^15N labeled nitrate. The mixtures of alanine, β-alanine, aspartic acid, asparagines, glutamic ac...In this paper, the role of mixed amino acids in nitrate uptake and assimilation was evaluated in leafy radish by using ^15N labeled nitrate. The mixtures of alanine, β-alanine, aspartic acid, asparagines, glutamic acid, glutamine, and glycine were sprayed to plant leaf two or four times. The activity of the enzymes related to the process of NO3- reduction （nitrate reductase, nitrite reductase and glutamine synthetase） was affected differently depending on the application rate of mixed amino acids. Applying mixed amino acids increased the fresh weight, dry weight, and N yield. The NO3 content was reduced to 24-38%, but no significant differences were observed in amino acids and proteins. In addition, the nitrogen derived from fertilizer and the ^15N-NO3-recovery rate increased to 2-8% and 15-47%, respectively. These results strongly suggest that the positive effect of mixed amino acids on nitrate uptake and assimilation might be attributed to the regulation on NO3- uptake and assimilation, but not to the preference for amino acids as sources of reduced nitrogen.展开更多
This paper investigated the effects of root-zone (RZ) CO<sub>2</sub> concentration ([CO<sub>2</sub>]) on root morphology and growth, nitrate (NO<sub>3</sub>-</sup>) uptake and...This paper investigated the effects of root-zone (RZ) CO<sub>2</sub> concentration ([CO<sub>2</sub>]) on root morphology and growth, nitrate (NO<sub>3</sub>-</sup>) uptake and assimilation of lettuce plants at different root-zone temperatures (RZT). Elevated RZ [CO<sub>2</sub>] stimulated root development, root and shoot growth compared to ambient RZ [CO<sub>2</sub>]. The greatest increase in root growth was observed in plants grown under elevated RZ [CO<sub>2</sub>] of 50,000 ppm. However, RZ [CO<sub>2</sub>] of 10,000 ppm was sufficient to achieve the maximal leaf area and shoot productivity. Lettuce plants exhibited faster shoot and root growth at 20°C-RZT than at ambient (A)-RZT. However, under elevated RZ [CO<sub>2</sub>], the magnitude of increased growth was greater at A-RZT than at 20°C-RZT. Compared to RZ [CO<sub>2</sub>] of 360 ppm, elevated RZ [CO<sub>2</sub>] of 10,000 ppm increased NO<sub>3</sub>-</sup> accumulation and nitrate reductase activity (NRA) in both leaves and roots. NO<sub>3</sub>-</sup> concentrations of leaf and root were higher at 20°C-RZT than at A-RZT in all plants. NRA was higher in root than in leaf especially under A-RZT. The total reduced nitrogen (TRN) concentration was significantly higher in plants grown under elevated RZ [CO<sub>2</sub>] of 10,000 ppm than under ambient RZ [CO<sub>2</sub>] of 360 ppm with greater concentration in 20°C-RZT plants than in A-RZT plants. These results imply that elevated RZ [CO<sub>2</sub>] significantly affected root morphology, root and shoot growth and N metabolism of temperate lettuce with greater impacts at A-RZT than at 20°C-RZT. These findings have practical significance to vegetable production by growing the vegetable crops at cool-RZT with elevated RZ [CO<sub>2</sub>] to enhance its productivity.展开更多
The dual isotopes(N and O)of nitrate were measured using a denitrifier bacterial method in the western South China Sea(WSCS)during September 2015 to elucidate key information during N transformation in the lower eupho...The dual isotopes(N and O)of nitrate were measured using a denitrifier bacterial method in the western South China Sea(WSCS)during September 2015 to elucidate key information during N transformation in the lower euphotic zone(LEZ)-upper mesopelagic zone(UMZ,down to 500 m in this study)continuum,which is a vital sub-environment for marine N cycle and sequestration of atmospheric CO_(2)as well.The N isotopic composition(δ^(15)N)of nitrate generally decreased from 500 m toward the base of the euphotic zone(∼100 m),reaching a value of∼4.6‰(vs.air N_(2))at the base of the LEZ,suggesting the imprint of remineralization(nitrification)of isotopically light N from atmospheric source.Theδ^(15)N andδ18O of nitrate only generally conform to a 1:1 line at 50 m and 75 m,suggesting that nitrate assimilation is a dominant process to shape nitrate isotope signature in this light-limited and relatively N-replete lower part of the euphotic zone.The fractionation factors of N and O isotopes during nitrate fractionation(15εASSIM,18εASSIM)using a steady-state model were estimated to be 4.0‰±0.3‰and 5.4‰±0.3‰,respectively.The occurrence of nitrification at the base of the LEZ and most of the UMZ is corroborated by the decoupling ofδ^(15)N and the oxygen isotopic composition(δ18O)of nitrate.Our results will provide insights for better understanding N cycle in the South China Sea from a perspective of present and past.展开更多
In this study, we conducted investigations in the Changjiang （Yangtze） River estuary and adjacent waters （CREAW） in June and November of 2014. We collected water samples from different depths to analyze the nitrog...In this study, we conducted investigations in the Changjiang （Yangtze） River estuary and adjacent waters （CREAW） in June and November of 2014. We collected water samples from different depths to analyze the nitrogen isotopic compositions of nitrate, nutrient concentrations （including inorganic N, P, and Si）, and other physical and biological parameters, along with the vertical distribution and seasonal variations of these parameters. The compositions of nitrogen isotope in nitrate were measured with the denitrifier method. Results show that the Changjiang River diluted water （CDW） was the main factor affecting the shallow waters （above 10 m） of the CREAW, and CDW tended to influence the northern areas in June and the southern areas in November. 615Nrqo~ values in CDW ranged from 3.21%o-3.55%o. In contrast, the deep waters （below 30 m） were affected by the subsurface water of the Kuroshio Current, which intruded into the waters near 3 I^N in June. The ~iI^NNo3 values of these waters were 6.03%0-7.6%0, slightly higher than the values of the Kuroshio Current. Nitrate assimilation by phytoplankton in the shallow waters of the study area varied seasonally. Because of the favorable temperature and nutrient conditions in June, abundant phytoplankton growth resulted in harmful algae blooms （HABs）. Therefore, nitrate assimilation was strong in June and weak in November. The ~15NNo3 fractionations caused by assimilation of phytoplankton were 4.57%0 and 4.41%o in the shallow waters in June and November, respectively. These results are consistent with previous laboratory cultures and in situ investigations. Nitrification processes were observed in some deep waters of the study area, and they were more apparent in November than in June. The fractionation values of nitrification ranged from 24%0-25%o, which agrees with results for Nitrosospira tenuis reported by previous studies.展开更多
Irradiated seeds of Phaseolus vulgaris cv. Rajmah using Synchroton X-Ray Beam (BL-07) at RRCAT, Indore at various doses in the range of 0.5 - 10 Gy were used to raise the seedling and the growth status at different st...Irradiated seeds of Phaseolus vulgaris cv. Rajmah using Synchroton X-Ray Beam (BL-07) at RRCAT, Indore at various doses in the range of 0.5 - 10 Gy were used to raise the seedling and the growth status at different stages was evaluated. Prior to germination, in the seeds soaked for 24 hours, the water regain remained unaffected by seed irradiation at 1 - 10 Gy doses, while the acid phosphatase activity was significantly reduced. Strong correlation (R2 = 0.685) between irradiation dose and enzyme activity also resulted. Analysing seed irradiation effect on seed development up to 4 days, % germination, germination index (GI), seedling wt, and seedling vigour were non significantly decreased at 5.0 Gy dose. The overall growth of 10 days old seedlings raised from irradiated seeds was substantially reduced at irradiation doses of 2?and 5 Gy exerting strong -ve correlation. Also % germination and seed vigour index (SVI) were prominently decreased due to seed irradiation. The nitrogen status of the seedlings, reflected by nitrate reductase activity (NRA) was significantly reduced in response to irradiation exerting strong correlation. The results demonstrate decreased phosphate mobilization in soaked seeds, time dependent decreased growth being more substantial with longer duration and reduced nitrate assimilation due to seed irradiation with Synchroton X-Ray Beam.展开更多
Pyropia haitanensis, a commercially important species, was cultured at two CO2 concentrations （390× 10^-6 and 700× 10^-6 （parts per million）） and at low and high nutrient levels, to explore the effect of...Pyropia haitanensis, a commercially important species, was cultured at two CO2 concentrations （390× 10^-6 and 700× 10^-6 （parts per million）） and at low and high nutrient levels, to explore the effect of elevated CO2 on the species under nutrient enrichment. Results show that in CO2-enriched thalli, relative growth rate （RGR） was enhanced under nutrient enrichment. Elevated CO2 decreased phycobiliprotein （PB） contents, but increased the contents of soluble carbohydrates. Nutrient enrichment increased the contents of chlorophyll a （Chl a） and PB, while soluble carbohydrate content decreased. CO2 enrichment enhanced the relative maximum electronic transport rate and light saturation point. In nutrient-enriched thalli the activity of nitrate reductase （NRA） increased under elevated CO2. An instantaneous pH change in seawater （from 8.1 to 9.6） resulted in reduction of NRA, and the thalli grown under both elevated CO2 and nutrient enrichment exhibited less pronounced reduction than in algae grown at the ambient CO2. The thermal optima of NRA under elevated CO2 and/or nutrient enrichment shifted to a lower temperature （10-15 ℃） compared to that in ambient conditions （20℃）. We propose that accelerated photosynthesis could result in growth increment. N assimilation remained high in acidified seawater and reflected increased temperature sensitivity in response to elevated CO_2 and eutrophication.展开更多
Bacteria are key denitrifiers in the reduction of nitrate(NO_(3)^(-)N),which is a contaminant in wastewater treatment plants(WWTPs).They can also produce carbon dioxide(CO_(2))and nitrous oxide(N2O).In this study,the ...Bacteria are key denitrifiers in the reduction of nitrate(NO_(3)^(-)N),which is a contaminant in wastewater treatment plants(WWTPs).They can also produce carbon dioxide(CO_(2))and nitrous oxide(N2O).In this study,the autotrophic hydrogen-oxidizing bacterium Rhodoblastus sp.TH_(2)0 was isolated for sustainable treatment of NO_(3)^(-)N in wastewater.Efficient removal of NO_(3)^(-)N and recovery of biomass nitrogen were achieved.Up to 99%of NO_(3)^(-)N was removed without accumulation of nitrite and N2O,consuming CO_(2)of 3.25 mol for each mole of NO_(3)^(-)N removed.The overall removal rate of NO_(3)^(-)N reached 1.1 mg L^(-1)h^(-1)with a biomass content of approximately 0.71 g L^(-1)within 72 h.TH20 participated in NO_(3)^(-)N assimilation and aerobic denitrification.Results from 15N-labeled-nitrate test indicated that removed NO_(3)^(-)N was assimilated into organic nitrogen,showing an assimilation efficiency of 58%.Seventeen amino acids were detected,accounting for 43%of the biomass.Nitrogen loss through aerobic denitrification was only approximately 42%of total nitrogen.This study suggests that TH_(2)0 can be applied in WWTP facilities for water purification and production of valuable biomass to mitigate CO_(2)and N_(2)O emissions。展开更多
Natural nitrogen isotope composition(δ^(15)N) is an indicator of nitrogen sources and is useful in the investigation of nitrogen cycling in organisms and ecosystems. δ^(15)N is also used to study assimilation of ino...Natural nitrogen isotope composition(δ^(15)N) is an indicator of nitrogen sources and is useful in the investigation of nitrogen cycling in organisms and ecosystems. δ^(15)N is also used to study assimilation of inorganic nitrogen. However, the foliar δ^(15)N of intact plants, which is a consequence of nitrate assimilation occurring in the roots and shoots, is not suited for studying nitrate assimilation in cases where nitrate is the sole nitrogen source. In this study, Orychophragmus violaceus(Ov) and Brassica napus(Bn) plantlets, in which nitrate assimilation occurred in the leaves, were used to study the relationship between foliar δ^(15)N and nitrate assimilation.The plantlets were grown in vitro in culture media with different nitrate concentrations, and no root formation occurred for the plantlets during the multiplication stage.Nitrogen isotope fractionation occurred in both the Ov and the Bn plantlets under all treatments. Furthermore, the foliar nitrogen content of both the Ov and Bn plantlets increased with increasing nitrate concentration. Foliar nitrogen isotope fractionation was negatively correlated with foliar nitrogen content for both the Ov and Bn plantlets. Our results suggest that the foliar nitrogen isotope fractionation value could be employed to evaluate nitrate assimilation ability and leaf nitrate reductase activity.Moreover, high external nitrate concentrations couldcontribute to improved foliar nitrogen content and enhanced nitrate assimilation ability.展开更多
Nitrate assimilation is a process where bacteria utilize nitrate as a nitrogen source and synthesize it into organic nitrogen. We found that nitrate-assimilating bacteria(NAB) are widely distributed in various marine ...Nitrate assimilation is a process where bacteria utilize nitrate as a nitrogen source and synthesize it into organic nitrogen. We found that nitrate-assimilating bacteria(NAB) are widely distributed in various marine environments, from surface to the deep ocean and sediment, which indicates that NAB are significant to the oceanic nitrogen cycle. Comparative genomic analysis revealed nitrate-assimilating genes(nas A) in these marine heterotrophic NAB showed different gene arrangements and diverse regulation systems. Summary on recent findings will contribute to understanding the process of nitrate assimilation in NAB and their ecological significance in the nitrogen cycle. A systematic analysis of a number of studies on bacterial nitrate assimilation in marine ecological systems was conducted to clarify directions for future research.展开更多
The physical stresses associated with emersion have long been considered major factors determining the vertical zona- tion of intertidal seaweeds. We examined Porphyra umbilicalis （Linnaeus） Kiitzing thalli from the...The physical stresses associated with emersion have long been considered major factors determining the vertical zona- tion of intertidal seaweeds. We examined Porphyra umbilicalis （Linnaeus） Kiitzing thalli from the vertical extremes in elevation of an intertidal population （i.e. upper and lower intertidal zones） to determine whether Porphyra thalli acclimate to different vertical elevations on the shore with different patterns of nitrate uptake and nitrate reductase （NR） and glutamine synthetase （GS） activities in response to different degrees of emersion stress. We found that the nitrate uptake and NR recovery in the emersed tissues took longer in lower intertidal sub-population than in upper intertidal sub-population; and GS activity was also significantly affected by emersion and, interestingly, such an activity was enhanced by emersion of thalli from both upper and lower intertidal zones. These results sug- gested that intta-population variability in post-emersion recovery of physiological functions such as nutrient uptake and NR activity enables local adaptation and contributes to the wide vertical distribution ofP. umbilicalis. The high GS activity during periodic emer- sion stress may be a protective mechanism enabling P umbilicalis to assimilate nitrogen quickly when it again becomes available, and may also be an evidence ofphotorespiration during emersion.展开更多
基金This work was supported by grants from the Natural Science Foundation of China(31325024 and 31601742)the Ministry of Education of China(IRT15R42)and Shandong Province Government(SDAIT-06-03).
文摘The basic leucine zipper(bZIP)transcription factor HY5 plays a multifaceted role in plant growth and development.Here the apple MdHY5 gene was cloned based on its homology with Arabidopsis HY5.Expression analysis demonstrated that MdHY5 transcription was induced by light and abscisic acid treatments.Electrophoretic mobility shift assays and transient expression assays subsequently showed that MdHY5 positively regulated both its own transcription and that of MdMYB10 by binding to E-box and G-box motifs,respectively.Furthermore,we obtained transgenic apple calli that overexpressed the MdHY5 gene,and apple calli coloration assays showed that MdHY5 promoted anthocyanin accumulation by regulating expression of the MdMYB10 gene and downstream anthocyanin biosynthesis genes.In addition,the transcript levels of a series of nitrate reductase genes and nitrate uptake genes in both wild-type and transgenic apple calli were detected.In association with increased nitrate reductase activities and nitrate contents,the results indicated that MdHY5 might be an important regulator in nutrient assimilation.Taken together,these results indicate that MdHY5 plays a vital role in anthocyanin accumulation and nitrate assimilation in apple.
基金supported by the Major Program of Guangdong Basic and Applied Research (2019B030302006)
文摘Nitrogen(N)is the driving force for crop yields;however,excessive N application in agriculture not only increases production cost,but also causes severe environmental problems.Therefore,comprehensively understanding the molecular mechanisms of N use efficiency(NUE)and breeding crops with higher NUE is essential to tackle these problems.NUE of crops is determined by N uptake,transport,assimilation,and remobilization.In the process of N assimilation,nitrate reductase(NR),nitrite reductase(Ni R),glutamine synthetase(GS),and glutamine-2-oxoglutarate aminotransferase(GOGAT,also known as glutamate synthase)are the major enzymes.NR and Ni R mediate the initiation of inorganic N utilization,and GS/GOGAT cycle converts inorganic N to organic N,playing a vital role in N assimilation and the final NUE of crops.Besides,asparagine synthetase(ASN),glutamate dehydrogenase(GDH),and carbamoyl phosphate synthetase(CPSase)are also involved.In this review,we summarize the function and regulation of these enzymes reported in three major crops—rice,maize,and wheat,also in the model plant Arabidopsis,and we highlight their application in improving NUE of crops via manipulating N assimilation.Anticipated challenges and prospects toward fully understanding the function of N assimilation and further exploring the potential for NUE improvement are discussed.
文摘Effects of water stress and foliar boron (FB) application on soybean (Glycine max (L) Merr.) seed composition and nitrogen metabolism have not been well investigated. Therefore, the objective of this study was to investigate the effects of water stress and FB on seed protein, oil, fatty acids, nitrate reductase activity (NRA), and nitrogenase activity (NA). A repeated greenhouse experiment was conducted where one set of soybean plants were subjected to water stress (WS), and the other set was watered (W). Foliar boron (B) was applied at rate of 0.45 kg·ha-1. Treatments were watered-plants with no FB (W), watered-plants with FB (WB), water-stress plants with no FB (WS), and water-stress plants with FB (WSB). The results showed that seed protein and oil percentage were significantly (P 15N/ 14N and 13C/12C natural abundance were altered between watered-and watered-stressed plants. These results suggest that water stress and FB can influence seed composition, and nitrogen metabolism, and 15N/14N and 13C/12C ratios, reflecting environmental and metabolic changes in carbon and nitrogen fixation pathways. Lack of B translocation from leaves to seed under water stress may suggest a possible mechanism of limited B translocation under water stress. These findings may be beneficial to breeders to select for B translocation efficiency under drought conditions. Altered 15N/14N and 13C/12C under water stress can be used as a tool to select for drought tolerance using N and C isotopes in the breeding programs.
基金the Science Foundation of Zhejiang Forestry University, China (2006FR011)
文摘In this paper, the role of mixed amino acids in nitrate uptake and assimilation was evaluated in leafy radish by using ^15N labeled nitrate. The mixtures of alanine, β-alanine, aspartic acid, asparagines, glutamic acid, glutamine, and glycine were sprayed to plant leaf two or four times. The activity of the enzymes related to the process of NO3- reduction （nitrate reductase, nitrite reductase and glutamine synthetase） was affected differently depending on the application rate of mixed amino acids. Applying mixed amino acids increased the fresh weight, dry weight, and N yield. The NO3 content was reduced to 24-38%, but no significant differences were observed in amino acids and proteins. In addition, the nitrogen derived from fertilizer and the ^15N-NO3-recovery rate increased to 2-8% and 15-47%, respectively. These results strongly suggest that the positive effect of mixed amino acids on nitrate uptake and assimilation might be attributed to the regulation on NO3- uptake and assimilation, but not to the preference for amino acids as sources of reduced nitrogen.
文摘This paper investigated the effects of root-zone (RZ) CO<sub>2</sub> concentration ([CO<sub>2</sub>]) on root morphology and growth, nitrate (NO<sub>3</sub>-</sup>) uptake and assimilation of lettuce plants at different root-zone temperatures (RZT). Elevated RZ [CO<sub>2</sub>] stimulated root development, root and shoot growth compared to ambient RZ [CO<sub>2</sub>]. The greatest increase in root growth was observed in plants grown under elevated RZ [CO<sub>2</sub>] of 50,000 ppm. However, RZ [CO<sub>2</sub>] of 10,000 ppm was sufficient to achieve the maximal leaf area and shoot productivity. Lettuce plants exhibited faster shoot and root growth at 20°C-RZT than at ambient (A)-RZT. However, under elevated RZ [CO<sub>2</sub>], the magnitude of increased growth was greater at A-RZT than at 20°C-RZT. Compared to RZ [CO<sub>2</sub>] of 360 ppm, elevated RZ [CO<sub>2</sub>] of 10,000 ppm increased NO<sub>3</sub>-</sup> accumulation and nitrate reductase activity (NRA) in both leaves and roots. NO<sub>3</sub>-</sup> concentrations of leaf and root were higher at 20°C-RZT than at A-RZT in all plants. NRA was higher in root than in leaf especially under A-RZT. The total reduced nitrogen (TRN) concentration was significantly higher in plants grown under elevated RZ [CO<sub>2</sub>] of 10,000 ppm than under ambient RZ [CO<sub>2</sub>] of 360 ppm with greater concentration in 20°C-RZT plants than in A-RZT plants. These results imply that elevated RZ [CO<sub>2</sub>] significantly affected root morphology, root and shoot growth and N metabolism of temperate lettuce with greater impacts at A-RZT than at 20°C-RZT. These findings have practical significance to vegetable production by growing the vegetable crops at cool-RZT with elevated RZ [CO<sub>2</sub>] to enhance its productivity.
基金The National Natural Science Foundation of China under contract Nos 42076042 and 41721005the Science and Technology Basic Resources Investigation Program of China under contract No.2017FY201403.
文摘The dual isotopes(N and O)of nitrate were measured using a denitrifier bacterial method in the western South China Sea(WSCS)during September 2015 to elucidate key information during N transformation in the lower euphotic zone(LEZ)-upper mesopelagic zone(UMZ,down to 500 m in this study)continuum,which is a vital sub-environment for marine N cycle and sequestration of atmospheric CO_(2)as well.The N isotopic composition(δ^(15)N)of nitrate generally decreased from 500 m toward the base of the euphotic zone(∼100 m),reaching a value of∼4.6‰(vs.air N_(2))at the base of the LEZ,suggesting the imprint of remineralization(nitrification)of isotopically light N from atmospheric source.Theδ^(15)N andδ18O of nitrate only generally conform to a 1:1 line at 50 m and 75 m,suggesting that nitrate assimilation is a dominant process to shape nitrate isotope signature in this light-limited and relatively N-replete lower part of the euphotic zone.The fractionation factors of N and O isotopes during nitrate fractionation(15εASSIM,18εASSIM)using a steady-state model were estimated to be 4.0‰±0.3‰and 5.4‰±0.3‰,respectively.The occurrence of nitrification at the base of the LEZ and most of the UMZ is corroborated by the decoupling ofδ^(15)N and the oxygen isotopic composition(δ18O)of nitrate.Our results will provide insights for better understanding N cycle in the South China Sea from a perspective of present and past.
基金Supported by the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA11020302)the National Natural Science Foundation of China(No.41276116)the NSFC-Shandong Joint Fund for Marine Science Research Centers(No.U 1406403)
文摘In this study, we conducted investigations in the Changjiang （Yangtze） River estuary and adjacent waters （CREAW） in June and November of 2014. We collected water samples from different depths to analyze the nitrogen isotopic compositions of nitrate, nutrient concentrations （including inorganic N, P, and Si）, and other physical and biological parameters, along with the vertical distribution and seasonal variations of these parameters. The compositions of nitrogen isotope in nitrate were measured with the denitrifier method. Results show that the Changjiang River diluted water （CDW） was the main factor affecting the shallow waters （above 10 m） of the CREAW, and CDW tended to influence the northern areas in June and the southern areas in November. 615Nrqo~ values in CDW ranged from 3.21%o-3.55%o. In contrast, the deep waters （below 30 m） were affected by the subsurface water of the Kuroshio Current, which intruded into the waters near 3 I^N in June. The ~iI^NNo3 values of these waters were 6.03%0-7.6%0, slightly higher than the values of the Kuroshio Current. Nitrate assimilation by phytoplankton in the shallow waters of the study area varied seasonally. Because of the favorable temperature and nutrient conditions in June, abundant phytoplankton growth resulted in harmful algae blooms （HABs）. Therefore, nitrate assimilation was strong in June and weak in November. The ~15NNo3 fractionations caused by assimilation of phytoplankton were 4.57%0 and 4.41%o in the shallow waters in June and November, respectively. These results are consistent with previous laboratory cultures and in situ investigations. Nitrification processes were observed in some deep waters of the study area, and they were more apparent in November than in June. The fractionation values of nitrification ranged from 24%0-25%o, which agrees with results for Nitrosospira tenuis reported by previous studies.
文摘Irradiated seeds of Phaseolus vulgaris cv. Rajmah using Synchroton X-Ray Beam (BL-07) at RRCAT, Indore at various doses in the range of 0.5 - 10 Gy were used to raise the seedling and the growth status at different stages was evaluated. Prior to germination, in the seeds soaked for 24 hours, the water regain remained unaffected by seed irradiation at 1 - 10 Gy doses, while the acid phosphatase activity was significantly reduced. Strong correlation (R2 = 0.685) between irradiation dose and enzyme activity also resulted. Analysing seed irradiation effect on seed development up to 4 days, % germination, germination index (GI), seedling wt, and seedling vigour were non significantly decreased at 5.0 Gy dose. The overall growth of 10 days old seedlings raised from irradiated seeds was substantially reduced at irradiation doses of 2?and 5 Gy exerting strong -ve correlation. Also % germination and seed vigour index (SVI) were prominently decreased due to seed irradiation. The nitrogen status of the seedlings, reflected by nitrate reductase activity (NRA) was significantly reduced in response to irradiation exerting strong correlation. The results demonstrate decreased phosphate mobilization in soaked seeds, time dependent decreased growth being more substantial with longer duration and reduced nitrate assimilation due to seed irradiation with Synchroton X-Ray Beam.
基金Supported by the National Natural Science Foundation of China(Nos.41276148,41076094)
文摘Pyropia haitanensis, a commercially important species, was cultured at two CO2 concentrations （390× 10^-6 and 700× 10^-6 （parts per million）） and at low and high nutrient levels, to explore the effect of elevated CO2 on the species under nutrient enrichment. Results show that in CO2-enriched thalli, relative growth rate （RGR） was enhanced under nutrient enrichment. Elevated CO2 decreased phycobiliprotein （PB） contents, but increased the contents of soluble carbohydrates. Nutrient enrichment increased the contents of chlorophyll a （Chl a） and PB, while soluble carbohydrate content decreased. CO2 enrichment enhanced the relative maximum electronic transport rate and light saturation point. In nutrient-enriched thalli the activity of nitrate reductase （NRA） increased under elevated CO2. An instantaneous pH change in seawater （from 8.1 to 9.6） resulted in reduction of NRA, and the thalli grown under both elevated CO2 and nutrient enrichment exhibited less pronounced reduction than in algae grown at the ambient CO2. The thermal optima of NRA under elevated CO2 and/or nutrient enrichment shifted to a lower temperature （10-15 ℃） compared to that in ambient conditions （20℃）. We propose that accelerated photosynthesis could result in growth increment. N assimilation remained high in acidified seawater and reflected increased temperature sensitivity in response to elevated CO_2 and eutrophication.
基金the Shenzhen Fundamental Research Programs(JCYJ20180503182122539,JCYJ20180503182130795,and GXWD20201231165807007-20200810165349001)the National Natural Science Foundation of China(51939009).
文摘Bacteria are key denitrifiers in the reduction of nitrate(NO_(3)^(-)N),which is a contaminant in wastewater treatment plants(WWTPs).They can also produce carbon dioxide(CO_(2))and nitrous oxide(N2O).In this study,the autotrophic hydrogen-oxidizing bacterium Rhodoblastus sp.TH_(2)0 was isolated for sustainable treatment of NO_(3)^(-)N in wastewater.Efficient removal of NO_(3)^(-)N and recovery of biomass nitrogen were achieved.Up to 99%of NO_(3)^(-)N was removed without accumulation of nitrite and N2O,consuming CO_(2)of 3.25 mol for each mole of NO_(3)^(-)N removed.The overall removal rate of NO_(3)^(-)N reached 1.1 mg L^(-1)h^(-1)with a biomass content of approximately 0.71 g L^(-1)within 72 h.TH20 participated in NO_(3)^(-)N assimilation and aerobic denitrification.Results from 15N-labeled-nitrate test indicated that removed NO_(3)^(-)N was assimilated into organic nitrogen,showing an assimilation efficiency of 58%.Seventeen amino acids were detected,accounting for 43%of the biomass.Nitrogen loss through aerobic denitrification was only approximately 42%of total nitrogen.This study suggests that TH_(2)0 can be applied in WWTP facilities for water purification and production of valuable biomass to mitigate CO_(2)and N_(2)O emissions。
基金supported by the National Key Research and development Program of China (2016YFC0502602)the National Natural Science Foundation of China (U1612441)the project of high-level innovative talents of Guizhou Province [2015(4035)]
文摘Natural nitrogen isotope composition(δ^(15)N) is an indicator of nitrogen sources and is useful in the investigation of nitrogen cycling in organisms and ecosystems. δ^(15)N is also used to study assimilation of inorganic nitrogen. However, the foliar δ^(15)N of intact plants, which is a consequence of nitrate assimilation occurring in the roots and shoots, is not suited for studying nitrate assimilation in cases where nitrate is the sole nitrogen source. In this study, Orychophragmus violaceus(Ov) and Brassica napus(Bn) plantlets, in which nitrate assimilation occurred in the leaves, were used to study the relationship between foliar δ^(15)N and nitrate assimilation.The plantlets were grown in vitro in culture media with different nitrate concentrations, and no root formation occurred for the plantlets during the multiplication stage.Nitrogen isotope fractionation occurred in both the Ov and the Bn plantlets under all treatments. Furthermore, the foliar nitrogen content of both the Ov and Bn plantlets increased with increasing nitrate concentration. Foliar nitrogen isotope fractionation was negatively correlated with foliar nitrogen content for both the Ov and Bn plantlets. Our results suggest that the foliar nitrogen isotope fractionation value could be employed to evaluate nitrate assimilation ability and leaf nitrate reductase activity.Moreover, high external nitrate concentrations couldcontribute to improved foliar nitrogen content and enhanced nitrate assimilation ability.
基金National Key Basic Research Program of China (Grant No. 2013CB955700)
文摘Nitrate assimilation is a process where bacteria utilize nitrate as a nitrogen source and synthesize it into organic nitrogen. We found that nitrate-assimilating bacteria(NAB) are widely distributed in various marine environments, from surface to the deep ocean and sediment, which indicates that NAB are significant to the oceanic nitrogen cycle. Comparative genomic analysis revealed nitrate-assimilating genes(nas A) in these marine heterotrophic NAB showed different gene arrangements and diverse regulation systems. Summary on recent findings will contribute to understanding the process of nitrate assimilation in NAB and their ecological significance in the nitrogen cycle. A systematic analysis of a number of studies on bacterial nitrate assimilation in marine ecological systems was conducted to clarify directions for future research.
基金supported by grants to C.Yarish from the Perkin Elmer Analytical Division of E,G & G,Wellesley,MA,USA,Connecticut Sea Grant College Program (2001-2003)National Oceanic and Atmospheric Administration's National Marine Aquaculture Initiative (DOC/U.S.A.+2 种基金2001-2004)awards to J.K. Kim from the Department of Ecology and Evolutionary Biology,University of Connecticut (Ronald Bamford Award)from the Connecticut Museum of Natural History (Henry N. Andrew and Francis Rice Trainor Awards)
文摘The physical stresses associated with emersion have long been considered major factors determining the vertical zona- tion of intertidal seaweeds. We examined Porphyra umbilicalis （Linnaeus） Kiitzing thalli from the vertical extremes in elevation of an intertidal population （i.e. upper and lower intertidal zones） to determine whether Porphyra thalli acclimate to different vertical elevations on the shore with different patterns of nitrate uptake and nitrate reductase （NR） and glutamine synthetase （GS） activities in response to different degrees of emersion stress. We found that the nitrate uptake and NR recovery in the emersed tissues took longer in lower intertidal sub-population than in upper intertidal sub-population; and GS activity was also significantly affected by emersion and, interestingly, such an activity was enhanced by emersion of thalli from both upper and lower intertidal zones. These results sug- gested that intta-population variability in post-emersion recovery of physiological functions such as nutrient uptake and NR activity enables local adaptation and contributes to the wide vertical distribution ofP. umbilicalis. The high GS activity during periodic emer- sion stress may be a protective mechanism enabling P umbilicalis to assimilate nitrogen quickly when it again becomes available, and may also be an evidence ofphotorespiration during emersion.
