Paddy System with a Hybrid Rice Enhances Cyanobacteria Nostoc and Increases N_2 Fixation
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摘要
Biological nitrogen(N) fixation(BNF) plays a significant role in maintaining soil fertility in paddy field ecosystems. Rice variety influences BNF, but how different rice varieties regulate BNF and associated diazotroph communities has not been quantified. Airtight,field-based ~(15)N_2-labelling growth chamber experiments were used to assess the BNF capacity of different rice varieties. In addition,both the 16 S rRNA and nifH genes were sequenced to assess the influence of different rice varieties on bacterial and diazotrophic communities in paddy soils. After subjecting a rice-soil system to 74 d of continuous airtight, field-based ~(15)N_2 labelling in pots in a growth chamber, the amounts of fixed N were 22.3 and 38.9 kg ha~(-1) in inbred japonica(W23) and hybrid indica(IIY) rice cultivars planted in the rice-soil systems, respectively, and only 1%–2.5% of the fixed N was allocated to the rice plants and weeds. A greater abundance of diazotrophs was found in the surface soil(0–1 cm) under IIY than under W23. Sequencing of the 16 S rRNA gene showed significantly greater abundances of the cyanobacterial genera Nostoc, Anabaena, and Cylindrospermum under IIY than under W23.Sequencing of the nifH gene also showed a significantly greater abundance of Nostoc under IIY than under W23. These results indicate that the hybrid rice cultivar(IIY) promoted BNF to a greater extent than the inbred rice cultivar(W23) and that the increase in BNF might have been due to the enhanced heterocystous cyanobacteria Nostoc.
Biological nitrogen(N) fixation(BNF) plays a significant role in maintaining soil fertility in paddy field ecosystems. Rice variety influences BNF, but how different rice varieties regulate BNF and associated diazotroph communities has not been quantified. Airtight,field-based ~(15)N_2-labelling growth chamber experiments were used to assess the BNF capacity of different rice varieties. In addition,both the 16 S rRNA and nifH genes were sequenced to assess the influence of different rice varieties on bacterial and diazotrophic communities in paddy soils. After subjecting a rice-soil system to 74 d of continuous airtight, field-based ~(15)N_2 labelling in pots in a growth chamber, the amounts of fixed N were 22.3 and 38.9 kg ha~(-1) in inbred japonica(W23) and hybrid indica(IIY) rice cultivars planted in the rice-soil systems, respectively, and only 1%–2.5% of the fixed N was allocated to the rice plants and weeds. A greater abundance of diazotrophs was found in the surface soil(0–1 cm) under IIY than under W23. Sequencing of the 16 S rRNA gene showed significantly greater abundances of the cyanobacterial genera Nostoc, Anabaena, and Cylindrospermum under IIY than under W23.Sequencing of the nifH gene also showed a significantly greater abundance of Nostoc under IIY than under W23. These results indicate that the hybrid rice cultivar(IIY) promoted BNF to a greater extent than the inbred rice cultivar(W23) and that the increase in BNF might have been due to the enhanced heterocystous cyanobacteria Nostoc.
Biological nitrogen(N) fixation(BNF) plays a significant role in maintaining soil fertility in paddy field ecosystems. Rice variety influences BNF, but how different rice varieties regulate BNF and associated diazotroph communities has not been quantified. Airtight,field-based ~(15)N_2-labelling growth chamber experiments were used to assess the BNF capacity of different rice varieties. In addition,both the 16 S rRNA and nifH genes were sequenced to assess the influence of different rice varieties on bacterial and diazotrophic communities in paddy soils. After subjecting a rice-soil system to 74 d of continuous airtight, field-based ~(15)N_2 labelling in pots in a growth chamber, the amounts of fixed N were 22.3 and 38.9 kg ha~(-1) in inbred japonica(W23) and hybrid indica(IIY) rice cultivars planted in the rice-soil systems, respectively, and only 1%–2.5% of the fixed N was allocated to the rice plants and weeds. A greater abundance of diazotrophs was found in the surface soil(0–1 cm) under IIY than under W23. Sequencing of the 16 S rRNA gene showed significantly greater abundances of the cyanobacterial genera Nostoc, Anabaena, and Cylindrospermum under IIY than under W23.Sequencing of the nifH gene also showed a significantly greater abundance of Nostoc under IIY than under W23. These results indicate that the hybrid rice cultivar(IIY) promoted BNF to a greater extent than the inbred rice cultivar(W23) and that the increase in BNF might have been due to the enhanced heterocystous cyanobacteria Nostoc.
引文
App A A,Watanabe I,Ventura T S,Bravo M,Jurey C D.1986.The effect of cultivated and wild rice varieties on the nitrogen balance offlooded soil.Soil Sci.141:448-452.
Atekwana E A,Geyer C J.2018.Spatial and temporal variations in the geochemistry of shallow groundwater contaminated with nitrate at a residential site.Environ Sci Pollut Res.25:27155-27172.
Aulakh M S,Wassmann R,Bueno C,Kreuzwieser J,Rennenberg H.2001.Characterization of root exudates at different growth stages of ten rice(Oryza sativa L.)cultivars.Plant Biol.3:139-148.
Bei Q C,Liu G,Tang H Y,Cadisch G,Rasche F,Xie Z B.2013.Heterotrophic and phototrophic15N2fixation and distribution offixed15N in aflooded ricesoil system.Soil Biol Biochem.59:25-31.
Belnap J.2001.Factors influencing nitrogenfixation and nitrogen release in biological soil crusts.In Belnap J,Lange O L(eds.)Biological Soil Crusts:Structure,Function,and Management.Springer,Berlin Heidelberg.pp.241-261.
Bergersen F J.1970.The quantitative relationship between nitrogenfixation and the acetylene-reduction assay.Aust J Biol Sci.23:1015-1026.
Binladen J,Gilbert M T P,Bollback J P,Panitz F,Bendixen C,Nielsen R,Willerslev E.2007.The use of coded PCR primers enables high-throughput sequencing of multiple homolog amplification products by 454 parallel sequencing.PLoS ONE.2:e197.
Bremer E,van Kessel C.1990.Appraisal of the nitrogen-15natural-abundance method for quantifying dinitrogenfixation.Soil Sci Soc Am J.54:404-411.
Cao Q,Rediske R R,Yao L,Xie L Q.2018.Effect of microcystins on root growth,oxidative response,and exudation of rice(Oryza sativa).Ecotoxicol Environ Saf.149:143-149.
Caporaso J G,Kuczynski J,Stombaugh J,Bittinger K,Bushman F D,Costello E K,Fierer N,Pena A G,Goodrich J K,Gordon J I,Huttley G A,Kelley S T,Knights D,Koenig J E,Ley R E,Lozupone C A,McDonald D,Muegge B D,Pirrung M,Reeder J,Sevinsky J R,Turnbaugh P J,Walters W A,Widmann J,Yatsunenko T,Zaneveld J,Knight R.2010.QIIME allows analysis of high-throughput community sequencing data.Nat Methods.7:335-336.
Cassán F,Diaz-Zorita M.2016.Azospirillum sp.in current agriculture:From the laboratory to thefield.Soil Biol Biochem.103:117-130.
Charyulu P B B N,Nayak D N,Rao V R.1981.15N2 incorporation by rhizosphere soil influence of rice variety,organic matter and combined nitrogen.Plant Soil.59:399-405.
Cheng S H,Zhuang J Y,Fan Y Y,Du J H,Cao L Y.2007.Progress in research and development on hybrid rice:A super-domesticate in China.Ann Bot.100:959-966.
Cole J R,Wang Q,Fish J A,Chai B L,Mc Garrell D M,Sun Y N,Brown C T,Porras-Alfaro A,Kuske C R,Tiedje J M.2014.Ribosomal database project:Data and tools for high throughput rRNA analysis.Nucleic Acids Res.42:D633-D642.
Edgar R C.2010.Search and clustering orders of magnitude faster than BLAST.Bioinformatics.26:2460-2461.
Edgar R C,Haas B J,Clemente J C,Quince C,Knight R.2011.UCHIME improves sensitivity and speed of chimera detection.Bioinformatics.27:2194-2200.
Eskew D L,Eaglesham A R J,App A A.1981.Heterotrophic15N2fixation and distribution of newlyfixed nitrogen in a rice-flooded soil system.Plant Physiol.68:48-52.
Fish J A,Chai B L,Wang Q,Sun Y N,Brown C T,Tiedje J M,Cole J R.2013.FunGene:The functional gene pipeline and repository.Front Microbiol.4:291.
Hamady M,Walker J J,Harris J K,Gold N J,Knight R.2008.Error-correcting barcoded primers for pyrosequencing hundreds of samples in multiplex.Nat Methods.5:235-237.
Huang J,Xu C C,Ridoutt B G,Wang X C,Ren P A.2017.Nitrogen and phosphorus losses and eutrophication potential associated with fertilizer application to cropland in China.JClean Prod.159:171-179.
Issa A A,Abd-Alla M H,Ohyama T.2014.Nitrogenfixing cyanobacteria:Future prospect.In Ohyama T(ed.)Advances in Biology and Ecology of Nitrogen Fixation.IntechOpen,Rijeka.pp.23-48.
Ito O,Cabrera D,Watanabe I.1980.Fixation of dinitrogen-15 associated with rice plants.Appl Environ Microbiol.39:554-558.
Knauth S,Hurek T,Brar D,Reinhold-Hurek B.2005.Influence of different Oryza cultivars on expression of nifH gene pools in roots of rice.Environ Microbiol.7:1725-1733.
Kuenzer C,Knauer K.2013.Remote sensing of rice crop areas.Int J Remote Sens.34:2101-2139.
Kulasooriya S A,Roger P A,Barraquio W L,Watanabe I.1981.Epiphytic nitrogenfixation on deepwater rice.Soil Sci Plant Nutr.27:19-27.
Ladha J K,Reddy P M.2003.Nitrogenfixation in rice systems:State of knowledge and future prospects.Plant Soil.252:151-167.
Ladha J K,Tirol A C,Daroy M L G,Caldo G,Ventura W,Watanabe I.1986.Plant-associated N2fixation(C2H2-reduction)byfive rice varieties,and relationship with plant growth characters as affected by straw incorporation.Soil Sci Plant Nutr.32:91-106.
Ladha J K,Tirol-Padre A,Reddy C K,Cassman K G,Verma S,Powlson D S,van Kessel C,de B.Richter D,Chakraborty D,Pathak H.2016.Global nitrogen budgets in cereals:A50-year assessment for maize,rice,and wheat production systems.Sci Rep.6:19355.
Letunic I,Bork P.2007.Interactive Tree Of Life(iTOL):An online tool for phylogenetic tree display and annotation.Bioinformatics.23:127-128.
Magoc T,Salzberg S L.2011.FLASH:Fast length adjustment of short reads to improve genome assemblies.Bioinformatics.27:2957-2963.
Neyra C A,Hageman R H.1976.Relationships between carbon dioxide,malate,and nitrate accumulation and reduction in corn(Zea mays L.)seedlings.Plant Physiol.58:726-730.
Nilsson M,Bhattacharya J,Rai A N,Bergman B.2002.Colonization of roots of rice(Oryza sativa)by symbiotic Nostoc strains.New Phytol.156:517-525.
Nilsson M,Rasmussen U,Bergman B.2006.Cyanobacterial chemotaxis to extracts of host and nonhost plants.FEMSMicrobiol Ecol.55:382-390.
Ohyama T,Kumazawa K.1981.A simple method for the preparation,purification and storage of 15N2 gas for biological nitrogenfixation studies.Soil Sci Plant Nutr.27:263-265.
Okubo T,Ikeda S,Sasaki K,Ohshima K,Hattori M,Sato T,Minamisawa K.2014.Phylogeny and functions of bacterial communities associated withfield-grown rice shoots.Microbes Environ.29:329-332.
Peng S B,Tang Q Y,Zou Y B.2009.Current status and challenges of rice production in China.Plant Prod Sci.12:3-8.
Peter Wolk C.1996.Heterocyst formation.Annu Rev Genet.30:59-78.
Poly F,Monrozier L J,Bally R.2001.Improvement in the RFLPprocedure for studying the diversity of nifH genes in communities of nitrogenfixers in soil.Res Microbiol.152:95-103.
Quast C,Pruesse E,Yilmaz P,Gerken J,Schweer T,Yarza P,Peplies J,Gl?ckner F O.2013.The SILVA ribosomal RNAgene database project:Improved data processing and webbased tools.Nucleic Acids Res.41:D590-D596.
Quesada A,Fernández-Valiente E.1996.Relationship between abundance of N2-fixing cyanobacteria and environmental features of Spanish ricefields.Microb Ecol.32:59-71.
Rajaramamohan-Rao V.1976.Nitrogenfixation as influenced by moisture content,ammonium sulphate and organic sources in a paddy soil.Soil Biol Biochem.8:445-448.
Rangjaroen C,Rerkasem B,Teaumroong N,Sungthong R,Lumyong S.2014.Comparative study of endophytic and endophytic diazotrophic bacterial communities across rice landraces grown in the highlands of northern Thailand.Arch Microbiol.196:35-49.
Rekha K,Baskar B,Srinath S,Usha B.2018.Plant-growthpromoting rhizobacteria Bacillus subtilis RR4 isolated from rice rhizosphere induces malic acid biosynthesis in rice roots.Can J Microbiol.64:20-27.
Roger P A,Ladha J K.1992.Biological N2fixation in wetland ricefields:Estimation and contribution to nitrogen balance.Plant Soil.141:41-55.
Rosenstock T S,Liptzin D,Dzurella K,Fryjoff-Hung A,Hollander A,Jensen V,King A,Kourakos G,Mc Nally A,Pettygrove G S,Quinn J,Viers J H,Tomich T P,Harter T.2014.Agriculture’s contribution to nitrate contamination of Californian groundwater(1945-2005).J Environ Qual.43:895-907.
Sano Y,Fujii T,Iyama S,Hirota Y,Komagata K.1981.Nitrogenfixation in the rhizosphere of cultivated and wild rice strains.Crop Sci.21:758-761.
Shi S J,Richardson A E,O’Callaghan M,DeAngelis K M,Jones E E,Stewart A,Firestone M K,Condron L M.2011.Effects of selected root exudate components on soil bacterial communities.FEMS Microbiol Ecol.77:600-610.
Stewart W D P,Rowell P,Rai A N.1983.Cyanobacteriaeukaryotic plant symbioses.Ann Inst Pasteur Microbiol.134:205-228.
Stubner S.2002.Enumeration of 16S r DNA of Desulfotomaculum lineage 1 in ricefield soil by real-time PCR with SybrGreenTMdetection.J Microbiol Methods.50:155-164.
Tan Z Y,Hurek T,Reinhold-Hurek B.2003.Effect of N-fertilization,plant genotype and environmental conditions on nifH gene pools in roots of rice.Environ Microbiol.5:1009-1015.
Tang H Y,Liu G,Zhu J G,Kobayashi K.2015.Effects of elevated ozone concentration on CH4 and N2O emission from paddy soil under fully open-airfield conditions.Glob Change Biol.21:1727-1736.
Venkataraman G S.1979.Algal inoculation of ricefields.In International Rice Research Institute(IRRI)(ed.)Nitrogen and Rice.IRRI,Manila.pp.311-321.
Vitousek P M,Menge D N,Reed S C,Cleveland C C.2013.Biological nitrogenfixation:Rates,patterns and ecological controls in terrestrial ecosystems.Philos Trans B Biol Sci.368:20130119.
Walker T S,Bais H P,Grotewold E,Vivanco J M.2003.Root exudation and rhizosphere biology.Plant Physiol.132:44-51.
Wang Q,Quensen III J F,Fish J A,Lee T K,Sun Y N,Tiedje J M,Cole J R.2013.Ecological patterns of nifH genes in four terrestrial climatic zones explored with targeted metagenomics using FrameBot,a new informatics tool.mBio.4:e00592-13.
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Atekwana E A,Geyer C J.2018.Spatial and temporal variations in the geochemistry of shallow groundwater contaminated with nitrate at a residential site.Environ Sci Pollut Res.25:27155-27172.
Aulakh M S,Wassmann R,Bueno C,Kreuzwieser J,Rennenberg H.2001.Characterization of root exudates at different growth stages of ten rice(Oryza sativa L.)cultivars.Plant Biol.3:139-148.
Bei Q C,Liu G,Tang H Y,Cadisch G,Rasche F,Xie Z B.2013.Heterotrophic and phototrophic15N2fixation and distribution offixed15N in aflooded ricesoil system.Soil Biol Biochem.59:25-31.
Belnap J.2001.Factors influencing nitrogenfixation and nitrogen release in biological soil crusts.In Belnap J,Lange O L(eds.)Biological Soil Crusts:Structure,Function,and Management.Springer,Berlin Heidelberg.pp.241-261.
Bergersen F J.1970.The quantitative relationship between nitrogenfixation and the acetylene-reduction assay.Aust J Biol Sci.23:1015-1026.
Binladen J,Gilbert M T P,Bollback J P,Panitz F,Bendixen C,Nielsen R,Willerslev E.2007.The use of coded PCR primers enables high-throughput sequencing of multiple homolog amplification products by 454 parallel sequencing.PLoS ONE.2:e197.
Bremer E,van Kessel C.1990.Appraisal of the nitrogen-15natural-abundance method for quantifying dinitrogenfixation.Soil Sci Soc Am J.54:404-411.
Cao Q,Rediske R R,Yao L,Xie L Q.2018.Effect of microcystins on root growth,oxidative response,and exudation of rice(Oryza sativa).Ecotoxicol Environ Saf.149:143-149.
Caporaso J G,Kuczynski J,Stombaugh J,Bittinger K,Bushman F D,Costello E K,Fierer N,Pena A G,Goodrich J K,Gordon J I,Huttley G A,Kelley S T,Knights D,Koenig J E,Ley R E,Lozupone C A,McDonald D,Muegge B D,Pirrung M,Reeder J,Sevinsky J R,Turnbaugh P J,Walters W A,Widmann J,Yatsunenko T,Zaneveld J,Knight R.2010.QIIME allows analysis of high-throughput community sequencing data.Nat Methods.7:335-336.
Cassán F,Diaz-Zorita M.2016.Azospirillum sp.in current agriculture:From the laboratory to thefield.Soil Biol Biochem.103:117-130.
Charyulu P B B N,Nayak D N,Rao V R.1981.15N2 incorporation by rhizosphere soil influence of rice variety,organic matter and combined nitrogen.Plant Soil.59:399-405.
Cheng S H,Zhuang J Y,Fan Y Y,Du J H,Cao L Y.2007.Progress in research and development on hybrid rice:A super-domesticate in China.Ann Bot.100:959-966.
Cole J R,Wang Q,Fish J A,Chai B L,Mc Garrell D M,Sun Y N,Brown C T,Porras-Alfaro A,Kuske C R,Tiedje J M.2014.Ribosomal database project:Data and tools for high throughput rRNA analysis.Nucleic Acids Res.42:D633-D642.
Edgar R C.2010.Search and clustering orders of magnitude faster than BLAST.Bioinformatics.26:2460-2461.
Edgar R C,Haas B J,Clemente J C,Quince C,Knight R.2011.UCHIME improves sensitivity and speed of chimera detection.Bioinformatics.27:2194-2200.
Eskew D L,Eaglesham A R J,App A A.1981.Heterotrophic15N2fixation and distribution of newlyfixed nitrogen in a rice-flooded soil system.Plant Physiol.68:48-52.
Fish J A,Chai B L,Wang Q,Sun Y N,Brown C T,Tiedje J M,Cole J R.2013.FunGene:The functional gene pipeline and repository.Front Microbiol.4:291.
Hamady M,Walker J J,Harris J K,Gold N J,Knight R.2008.Error-correcting barcoded primers for pyrosequencing hundreds of samples in multiplex.Nat Methods.5:235-237.
Huang J,Xu C C,Ridoutt B G,Wang X C,Ren P A.2017.Nitrogen and phosphorus losses and eutrophication potential associated with fertilizer application to cropland in China.JClean Prod.159:171-179.
Issa A A,Abd-Alla M H,Ohyama T.2014.Nitrogenfixing cyanobacteria:Future prospect.In Ohyama T(ed.)Advances in Biology and Ecology of Nitrogen Fixation.IntechOpen,Rijeka.pp.23-48.
Ito O,Cabrera D,Watanabe I.1980.Fixation of dinitrogen-15 associated with rice plants.Appl Environ Microbiol.39:554-558.
Knauth S,Hurek T,Brar D,Reinhold-Hurek B.2005.Influence of different Oryza cultivars on expression of nifH gene pools in roots of rice.Environ Microbiol.7:1725-1733.
Kuenzer C,Knauer K.2013.Remote sensing of rice crop areas.Int J Remote Sens.34:2101-2139.
Kulasooriya S A,Roger P A,Barraquio W L,Watanabe I.1981.Epiphytic nitrogenfixation on deepwater rice.Soil Sci Plant Nutr.27:19-27.
Ladha J K,Reddy P M.2003.Nitrogenfixation in rice systems:State of knowledge and future prospects.Plant Soil.252:151-167.
Ladha J K,Tirol A C,Daroy M L G,Caldo G,Ventura W,Watanabe I.1986.Plant-associated N2fixation(C2H2-reduction)byfive rice varieties,and relationship with plant growth characters as affected by straw incorporation.Soil Sci Plant Nutr.32:91-106.
Ladha J K,Tirol-Padre A,Reddy C K,Cassman K G,Verma S,Powlson D S,van Kessel C,de B.Richter D,Chakraborty D,Pathak H.2016.Global nitrogen budgets in cereals:A50-year assessment for maize,rice,and wheat production systems.Sci Rep.6:19355.
Letunic I,Bork P.2007.Interactive Tree Of Life(iTOL):An online tool for phylogenetic tree display and annotation.Bioinformatics.23:127-128.
Magoc T,Salzberg S L.2011.FLASH:Fast length adjustment of short reads to improve genome assemblies.Bioinformatics.27:2957-2963.
Neyra C A,Hageman R H.1976.Relationships between carbon dioxide,malate,and nitrate accumulation and reduction in corn(Zea mays L.)seedlings.Plant Physiol.58:726-730.
Nilsson M,Bhattacharya J,Rai A N,Bergman B.2002.Colonization of roots of rice(Oryza sativa)by symbiotic Nostoc strains.New Phytol.156:517-525.
Nilsson M,Rasmussen U,Bergman B.2006.Cyanobacterial chemotaxis to extracts of host and nonhost plants.FEMSMicrobiol Ecol.55:382-390.
Ohyama T,Kumazawa K.1981.A simple method for the preparation,purification and storage of 15N2 gas for biological nitrogenfixation studies.Soil Sci Plant Nutr.27:263-265.
Okubo T,Ikeda S,Sasaki K,Ohshima K,Hattori M,Sato T,Minamisawa K.2014.Phylogeny and functions of bacterial communities associated withfield-grown rice shoots.Microbes Environ.29:329-332.
Peng S B,Tang Q Y,Zou Y B.2009.Current status and challenges of rice production in China.Plant Prod Sci.12:3-8.
Peter Wolk C.1996.Heterocyst formation.Annu Rev Genet.30:59-78.
Poly F,Monrozier L J,Bally R.2001.Improvement in the RFLPprocedure for studying the diversity of nifH genes in communities of nitrogenfixers in soil.Res Microbiol.152:95-103.
Quast C,Pruesse E,Yilmaz P,Gerken J,Schweer T,Yarza P,Peplies J,Gl?ckner F O.2013.The SILVA ribosomal RNAgene database project:Improved data processing and webbased tools.Nucleic Acids Res.41:D590-D596.
Quesada A,Fernández-Valiente E.1996.Relationship between abundance of N2-fixing cyanobacteria and environmental features of Spanish ricefields.Microb Ecol.32:59-71.
Rajaramamohan-Rao V.1976.Nitrogenfixation as influenced by moisture content,ammonium sulphate and organic sources in a paddy soil.Soil Biol Biochem.8:445-448.
Rangjaroen C,Rerkasem B,Teaumroong N,Sungthong R,Lumyong S.2014.Comparative study of endophytic and endophytic diazotrophic bacterial communities across rice landraces grown in the highlands of northern Thailand.Arch Microbiol.196:35-49.
Rekha K,Baskar B,Srinath S,Usha B.2018.Plant-growthpromoting rhizobacteria Bacillus subtilis RR4 isolated from rice rhizosphere induces malic acid biosynthesis in rice roots.Can J Microbiol.64:20-27.
Roger P A,Ladha J K.1992.Biological N2fixation in wetland ricefields:Estimation and contribution to nitrogen balance.Plant Soil.141:41-55.
Rosenstock T S,Liptzin D,Dzurella K,Fryjoff-Hung A,Hollander A,Jensen V,King A,Kourakos G,Mc Nally A,Pettygrove G S,Quinn J,Viers J H,Tomich T P,Harter T.2014.Agriculture’s contribution to nitrate contamination of Californian groundwater(1945-2005).J Environ Qual.43:895-907.
Sano Y,Fujii T,Iyama S,Hirota Y,Komagata K.1981.Nitrogenfixation in the rhizosphere of cultivated and wild rice strains.Crop Sci.21:758-761.
Shi S J,Richardson A E,O’Callaghan M,DeAngelis K M,Jones E E,Stewart A,Firestone M K,Condron L M.2011.Effects of selected root exudate components on soil bacterial communities.FEMS Microbiol Ecol.77:600-610.
Stewart W D P,Rowell P,Rai A N.1983.Cyanobacteriaeukaryotic plant symbioses.Ann Inst Pasteur Microbiol.134:205-228.
Stubner S.2002.Enumeration of 16S r DNA of Desulfotomaculum lineage 1 in ricefield soil by real-time PCR with SybrGreenTMdetection.J Microbiol Methods.50:155-164.
Tan Z Y,Hurek T,Reinhold-Hurek B.2003.Effect of N-fertilization,plant genotype and environmental conditions on nifH gene pools in roots of rice.Environ Microbiol.5:1009-1015.
Tang H Y,Liu G,Zhu J G,Kobayashi K.2015.Effects of elevated ozone concentration on CH4 and N2O emission from paddy soil under fully open-airfield conditions.Glob Change Biol.21:1727-1736.
Venkataraman G S.1979.Algal inoculation of ricefields.In International Rice Research Institute(IRRI)(ed.)Nitrogen and Rice.IRRI,Manila.pp.311-321.
Vitousek P M,Menge D N,Reed S C,Cleveland C C.2013.Biological nitrogenfixation:Rates,patterns and ecological controls in terrestrial ecosystems.Philos Trans B Biol Sci.368:20130119.
Walker T S,Bais H P,Grotewold E,Vivanco J M.2003.Root exudation and rhizosphere biology.Plant Physiol.132:44-51.
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