为探讨转C4光合基因水稻在生育后期剑叶PSⅡ对氮素水平的响应特性,采用转pepc(PC)、ppdk(PK)、pepc+ppdk(CK)和未转基因的Kitaake(WT)为试验材料,测定了不同氮素条件下(0.7 mmol/L(1/4N)、3 mmol/L(1N)、6mmol/L(2N))不同品种剑叶SPAD值和形态学指标的变化,并运用叶绿素荧光动力学技术测定了各个品种叶绿素荧光动力学曲线和荧光参数的变化。结果表明,1/4N处理能增加各品种的根长,减小剑叶面积、株高以及叶片叶绿素含量,2N能使剑叶面积和叶绿素含量增加,转C4光合基因品种叶绿素含量在1/4N氮条件下具有显著优势,PC在1/4N条件下具有最长根长和最大剑叶面积,具有显著的形态学优势。1/4N处理使所有品种的荧光曲线出现了K相(300μs处)的增加,转C4基因水稻材料K相的峰值都比原种低,PC的峰值最低。叶绿素荧光曲线分析表明,低氮破坏了剑叶PSⅡ的构造,造成所有品种PSⅡ的OEC失活,从而出现300μs处K相的增加,低氮还造成所有品种失活反应中心增加,电子传递活性减弱,热耗散增加,进而造成PSⅡ最大光化学活性的减小。而PC在低氮当中PSⅡ的所有指标都显著高于其他品种,具有相对稳定的PSⅡ结构,具有耐低氮的优势。高氮对各品种PSⅡ光化学活性的影响不大。
TheRe was close Relationship between nitRogen use efficiency and photosynthetic capability． C4 photosynthetic gene tRansgenic Rice had higheR light use efficiency and CO2 assimilation compaRed to tRaditional C3 Rice cultivaRs． HoweveR，whetheR nitRogen had influence on photosynthesis of these tRansgenic Rice cultivaRs was unknown ChloRophyll fluoRescence can Reflect intRinsic chaRacteRistics using fast measuRement without any damage to leaves， and is usually used as pRobe of photosynthesis． In the pResent study， the pepc ( PC) ，ppdk ( PK) and pepc + ppdk ( CK) tRansgenic Rice plants weRe used as expeRimental mateRials with theiR wild type Kitaaki( WT) to investigate the Responses of photosynthetic chaRacteRistics to diffeRent nitRogen levels in C4 photosynthetic gene tRansgenic Rice at the late RepRoductive stage． Changes in SPAD values，moRphological paRameteRs weRe measuRed in flag leaves of fouR cultivaRs undeR diffeRent nitRogen levels． The analysis of chloRophyll fluoRescence kinetic cuRves and some Related paRameteRs weRe also done undeR thRee nitRogen levels( 0． 7 mmol /L N-1 /4N low nitRogen，3 mmol /L N-1N contRol， 6 mmol /L N-2N high nitRogen) at the late RepRoductive stage using fast chloRophyll fluoRescence kinetic technology， in oRdeR to exploRe the effects of nitRogen on photosystem Ⅱ( PSⅡ) function of C4 photosynthetic gene tRansgenic Rice flag leaves． The Results showed that 1 /4N tReatment incReased Root length，decReased plant height， leaf aRea and chloRophyll contents of flag leaves in all cultivaRs，while 2N tReatment incReased leaf aRea and chloRophyll contents． C4 photosynthetic gene tRansgenic plants exposed to 1 /4N tReatment had higheR chloRophyll contents，and PC had longest Root length and laRgest leaf aRea of flag leaves，which indicated that they had moRe moRphological advantage undeR 1 /4N tReatment than wild type． The fluoRescence O-J-I-P cuRves changes weRe found in all cultivaRs undeR 1 /4N tReatment． The K phase( at 300 μs) incReased and C4 tRansgenic Rice had loweR K phase peak values compaRed to WT． TheRe was lowest value in PC． 1 /4N tReatment also incReased Fo( minimal fluoRescence) ，ABS /RC( absoRption flux peR Reaction centeR) ，TR0 /RC( tRapped eneRgy flux peR Reaction centeR) and DI0 /RC( dissipated eneRgy flux peR Reaction centeR) ，decReased Fv /FO ，ET0 /RC( electRon tRanspoRt flux peR Reaction centeR) ，φE0 ( quantum yield foR electRon tRanspoRt) and ψ0 ( pRobability that a tRapped exciton moves an electRon into the electRon tRanspoRt chain beyond QA - ) of all cultivaRs，Fm( maximal fluoRescence) of WT，RC /CS0 ( density of Reaction centeRs) of thRee cultivaRs except PC． The effects on fluoRescence paRameteRs weRe smalleR in PC than otheR cultivaRs exposed to low nitRogen． The analysis of chloRophyll fluoRescence kinetics indicated that the damaged PSⅡstRuctuRe of flag leaves could lead to the inactivation of OEC( oxygen-evolving complex) undeR low nitRogen，which attRibuted to the incRease of K phase in all cultivaRs． In addition， the numbeR of inactivated Reaction centeRs incReased，electRon tRanspoRt activities decReased and heat dissipation incReased，which attRibuted to the decRease of PSⅡ maximum photochemical activities． PC was moRe Resistant to low nitRogen than otheR cultivaRs since it showed higheR levels of paRameteRs Related to PSⅡ function，and moRe Relatively stable PSⅡ stRuctuRe． The effects of high nitRogen weRe smalleR on PSⅡ photochemical activities compaRed to those of low nitRogen．
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