title: [Effects of nitrogen application and elevated atmospheric CO2 on electron transport and energy partitioning in flag leaf photosynthesis of wheat].
abstract: Wheat (Triticum aestivum) plants were pot-cultured in open top chambers at the nitrogen application rate of 0 and 200 mg x kg(-1) soil and the atmospheric CO2 concentration of 400 and 760 micromol x mol(-1). Through the determination of flag leaf nitrogen and chlorophyll contents, photosynthetic rate (Pn)-intercellar CO2 concentration (Ci) response curve, and chlorophyll fluorescence parameters at heading stage, the photosynthetic electron transport rate and others were calculated, aimed to investigate the effects of nitrogen application and elevated atmospheric CO2 concentration on the photosynthetic energy partitioning in wheat flag leaves. Elevated atmospheric CO2 concentration decreased the leaf nitrogen and chlorophyll contents, compared with the ambient one, and the chlorophyll a/b ratio increased at the nitrogen application rate of 200 mg x kg(-1). With the application of nitrogen, no evident variations were observed in the maximal photochemical efficiency (Fv/Fm), maximal quantum yield under irradiance (Fv'/Fm') of PS II reaction center, photochemical fluorescence quenching coefficient (q(p)), and actual PS II efficiency under irradiance (phi(PS II) at elevated atmospheric CO2 concentration, and the total photosynthetic electron transport rate (J(F)) of PS II reaction center had no evident increase, though the non-photochemical fluorescence quenching coefficient (NPQ) decreased significantly. With no nitrogen application, the Fv'/Fm', psi(PS II), and NPQ at elevated atmospheric CO2 concentration decreased significantly, and the J(F) had a significant decrease though the Fv/Fm and q(p) did not vary remarkably. Nitrogen application increased the J(F) and photochemical electron transport rate (Jc); while elevated atmospheric CO2 concentration decreased the photorespiration electron transport rate (J0), Rubisco oxidation rate (V0), ratio of photorespiration to photochemical electron transport rate (J0/Jc) , and Rubisco oxidation/carboxylation rate (Vo/Vc), but increased the photochemical electron transport rate (Jc) and Rubisco carboxylation rate (Vc). It was concluded that elevated atmospheric CO2 concentration decreased the leaf nitrogen and chlorophyll contents, while nitrogen application increased the photosynthetic electron transport rate of PS II reaction center significantly, and promoted the photosynthetic electron flow towards photochemistry, making more photosynthetic electron take part in Rubisco carboxylation and leading to the significant increase of Pn.
authors.affiliation: Ministry of Agriculture Key Laboratory of Northwest Crop Drought-resistant Farming, Gansu Academy of Agricultural Sciences, Lanzhou 730070, China. gszhangxuch@163.com
authors.forename: Xu-cheng
authors.initials: XC
authors.lastname: Zhang
authors.forename: Xian-feng
authors.initials: XF
authors.lastname: Yu
authors.forename: Yi-fan
authors.initials: YF
authors.lastname: Ma
mesh_terms: D001272:Atmosphere / Q000032:analysis; D002245:Carbon Dioxide / Q000032:analysis*; D004579:Electron Transport; D004734:Energy Metabolism; D005308:Fertilizers; D009584:Nitrogen / Q000737:chemistry*; D010788:Photosynthesis / Q000502:physiology*; D018515:Plant Leaves / Q000502:physiology*; D014908:Triticum / Q000254:growth & development / Q000502:physiology*
chemical_list: D005308:Fertilizers; D002245:Carbon Dioxide; D009584:Nitrogen