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Root activity and nitrogen assimilation of rice(Oryza sativa)under Free-Air CO2 Enrichment

PANG Jing 1,2,ZHU Jianguo 1,XIE Zubin 1,LIU Gang 1,CHEN Gaiping 1,ZHANG Yali 1   

  1. 1State Key Laboratory of Soil and Sustainable Agriculture,Institute of Soil Science，Chinese Academy of Sciences,Nanjing 210008,China;2Faculty of Resource and Environment,Hubei University,Wuhan 430062,China
  • Received:2004-10-02 Revised:2005-02-21 Online:2005-08-18

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Abstract: With Free-Air CO2 Enrichment(FACE)technique,this paper studied the root activity and amino acid(aa) synthesis of rice(Oryza sativa)at low N(LN,150 kgN·hm-2)and normal N(NN,250 kgN·hm-2)under ambient air and elevated atmospheric CO2(Ambient+200 μmol·mol-1).Under elevated CO2,the xylem exudates per hill changed little,while the xylem exudates per stem declined by 1.4%～21.7% as the result of greater tiller numbers.At tillering and heading stages,elevated CO2 increased aa N/inorganic N in xylem exudates by 11.1%～143.1%,but did not affect the aa concentration in xylem exudates and the total amount of aa in roots significantly.However,at 35 days after heading,the aa N/inorganic N ratio decreased by 38.1%(LN)and 29.2%(NN)under elevated CO2.FACE also declined the aa concentration in xylem exudates by 34.0%(LN)and 44.7%(NN),and the total amount of aa by 50.8%(LN) and 40.0%(NN),which meant the retarded capability of aa synthesis in roots.N amendment led to a decrease of aa N/inorganic N in xylem exudates by 19.5%(Ambient) and 36.8%(FACE) at heading stage,as the result of unaffected aa and increased inorganic N concentration.There existed a significantly antagonistical CO2×N interaction on aa N/inorganic N at heading stage.