Effects Of Reducing Source On Grain Yield In Maize (Zea Mays L.) And Its Physiological Mechanisms

The experiment was carried out in the Maize Technological Innovation center in theYellow River Basin and the Huaihe River Basin and in the States Key Laboratory of CropBiology from2009to2011. This study used the technology line of integration of experimentin the field and conservatory with physiological and biochemical experiments indoor. TheZhengdan958(Z)and Xianyu335(X)were selected to research the effects of reducing sourceon grain yield and its physiological mechanisms in different plant density and applyingdifferent nitrogen. And the13C experiment was carried out to study the effects of reducingsource on the distribution of13C in the plant of maize. The results summaries were as follows:1Effect of reducing source on grain yield and grain quality characters1.1Grain yieldS2(Shearing top1-2spread leaves at silking stage), J6(Shearing six spread leaves at six spreadleaves stage), EB6(Shearing bottom six spread leaves at twelve stage) and SB6(Shearing top13-18spread leaves at silking stage) increased the grain yield(Except XD2N3S2<CK)；Othertreatments of reducing source decreased the grain yield. Number of kernels per ear of S2andSB6increased and J6and EB decreased；1000kernels weight of S2and SB6decreased and J6and EB increased. In addition, the photosynthetic rate and grain yield of S1(Shearing tassel atsilking stage) increased.1.2Biomass accumulationThe biomass accumulation rate of S2, J6, EB6and SB6(except D1N3S2and XSB6) increased and the biomass increased in the harvest.1.3Endosperm cell numbers,fresh volume and dry weight of grainEndosperm cell numbers, fresh volume and dry weight ingrain increased duringdevelopment. Endosperm cell numbers,fresh volume and dry weight in grain increased asapplying nitrogen increased and decreased as plant density increased. S2, J6,EB6and SB6increased endosperm cell numbers,fresh volume and dry weight of grain(Except XD1N3S2of fresh volume and dry weight in grain decreased)；Other treatments of reducing sourcedecreased endosperm cell numbers,fresh volume and dry weight of grain (Except XD3N3S3(Shearing top1-4spread leaves at silking stage) decreased endosperm cell numbers). The differencebetween the treatments of reducing source and control during the early grain filling stage wasnot significant.1.4The ration of grain and leaf,harvest indexThe treatments of reducing source increased grain/leaf and harvest index. That illustratedthat the treatments of reducing source could increase the transportation of photosyntheticproducts to grain.1.5Grain quality charactersS2, S3, S4(Shearing top1-6spread leaves at silking stage), J6, EB6, SB6and ZST6intreatments of reducing source increase total starch content, amylose content and amylopectincontent. Protein content of the reducing-source-treatments increased (except S18and ZE12).Soluble sugar content of S2, ZD3N3S3, XD3N3S3, ZJ6, ZEB6and ZSB6increased; Crudefat content of S2(S3of Zhengdan958, except for ZD3N3S3), ZD2N0S4, XJ6, EB6and SB6increased; Amino acid content of S2, ZD3N3S3, J6, EB6and SB6increased.2Effects of reducing source on distribution of carbon and nitrogen2.1Effects of reducing source on distribution of13C in every organAt anthesis-silking stage, after photosynthetic reaction with13CO2for24h, there wasthe most13C content in the leaf for reaction with13CO2among different leaf.13C content indifferent organs: ear>tassel>stem>leaf.13C content decreased in the leaf for reaction with13CO2from top to bottom, while13C content in ear increased. That illustrated thattransportation rate of photosynthetic products in the top leaf was faster than rate in bottomleaf. The treatments of reducing source increased13C content in the leaf for reaction with 13CO2(Except S3).At harvest stage,13C content in the leaf with reaction with13CO2reached maximumamong different leaf. There was13C content in the leaf of the reducing-source-treatments forreaction with13CO2among different leaf. There was most13C content in grain and the tasselwas the second.13C content in the grain and ear increased as applying nitrogen increased anddecreased as plant density increased.13C content of tassel decreased in the leaf for reactionwith13CO2from top to bottom.13C content of grain and ear increased.2.2Effects of reducing source on carbon content in every organAt anthesis-silking stage, there was most carbon content in the first or second leaf fromthe top. There was the most carbon content in the tassel. Carbon content in the tassel of thetreatments of reducing source decreased.At harvest stage, carbon content in7th (6th) leaf of the reducing-source-treatmentsdecreased. That illustrated that transportation rate of carbon from leaf to grain. Carbon contentin grain increased as applying nitrogen increased and there was the most carbon content in D2among different plant density. Carbon content in grain of the reducing-source-treatmentsdecreased.2.3Effects of reducing source on nitrogen content in every organAt anthesis-silking stage, nitrogen content in7th (6th) leaf of the reducing-source-treatments increased. There was more nitrogen content in tassel and leaf than nitrogen contentin stem and ear. Nitrogen content in tassel increased as applying nitrogen increased anddecreased as plant density increased. Nitrogen content in tassel of the reducing-source-treatments decreased.At harvest stage, nitrogen content in leaf of S2～S4increased and nitrogen content instem decreased. Nitrogen content in grain of S2increased. Nitrogen content in bract and cobof reducing-source-treatments increased. Nitrogen content in grain of ZET6increased.Nitrogen content in grain, stem and tassel decreased among ZST6～ZS18. Nitrogen content inbract and leaf increased. Nitrogen content in cob of ZS18increased.2.4Effects of reducing source on C/N in every organAt anthesis-silking stage, C/N in tassel and leaf of S2～S4increased, while C/N in stemand ear of S2～S4decreased. C/N in tassel and leaf of ZJ6, ZET6, ZEB6and ZE12decreased. C/N in stem and ear of ZJ6and ZEB6increased.At harvest stage, C/N in ear and leaf decreased. C/N in tassel of S2and S3increasedamong S2～S4. C/N in stem decreased among S2～S4. Only C/N in tassel of ZJ6, ZET6,ZSB6and ZS18increased and only C/N in stem of ZET6and ZS18decreased amongtreatments of reducing-source at different stage. C/N in leaf of reducing-source-treatmentsdecreased. Only C/N in ear of ZJ6, ZSB6and ZSB6increased. That illustrated that nitrogenaccumulation was more sensitive than carbon accumulation.3Starch granule morphogenesis and developmentThe proportion of number of diameter of starch granule lower than2μm was the most,while the proportion of volume of diameter lower than2μm was the least. The proportion ofnumber of diameter higher than15μm was the least, while the proportion of volume ofdiameter higher than15μm was the most (except the proportion of volume of diameterbetween2and15μm in Super-sweet corn grain was the most). The differences of theproportion of surface area in the different diameter classification were not significant (exceptthe proportion of surface area of diameter higher than15μm in Super-sweet corn grain wasthe least). Grain weight and total starch content value showed a positive correlation with theproportion of volume of diameter higher than2μm. The differenceamong various type maizewas significant. Higher applying nitrogen or lower plant density could speed up starch granuledevelopment. The effects of different reducing-source-treatments were different. And grainweight and quality was the result of combined effects of every cell in endosperm.4Leaf area index, photosynthetic rate and chloroplast ultrastructureReducing-source-treatments increased plant height and decreased stem diameter andtassel branch number at jointing stage and ear stage. Leaf area index of S0and S2drop inabout50DPA, while leaf area index of S3and S4drop in about40DPA. The period of theleaf area index drop was different in reducing-source-treatments at different stage.Photosynthetic rate of S2, J6, EB6and SB6increased (except XD2N0S2<S0at the late grainfilling stage); Photosynthetic rate of other treatments of reducing source increased at the earlygrain filling stage and decreased at the late grain filling stage (except ZD3N3S3, ZD3N3S4and XD3N3S3increased).chlorophyll a,chlorophyll b and chlorophyll a+b content of S2, J6, EB6and SB6 increased(except chlorophyll a and chlorophyll a+b: XD2N0S2<S0; chlorophyll b:XD2N0S2and ZD1N3S0decreased at the late grain filling stage); chlorophyll a,chlorophyllb and chlorophyll a+b content of other treatments of reducing source increased at the earlygrain filling stage and decreased at the late grain filling stage(except chlorophyll a andchlorophyll a+b: ZD3N3S3, ZD3N3S4and XD3N3S3increased; chlorophyll b:ZD3N3S3>S0). Carotenoid content of S2increased； Carotenoid content of ZD3N3S3increased at the early grain filling stage and decreased at the late grain filling stage. Andcarotenoid content of other treatments of reducing source decreased.Number of chloroplast in the mesophyll cell and number of grana lamellae inreducing-source-treatments increased. Ultrastructure grana lamellae in reducing-source-treatments were better than the control.Number leaf stoma in lower epidermis of ZJ6～ZE12decreased (except ZET6=Control).Number leaf stoma in lower and upper epidermis of reducing-source-treatments at silkingstage decreased. But the difference was not significant.5Key enzyme activity of leaf in carbon metabolismPEPCase and RUBPCase activity of S2, J6, EB6and SB6increased；PEPCase andRUBPCase activity of other treatments of reducing source increased at the early grain fillingstage and decreased at the late grain filling stage(except ZD3N3S3>S0).SPS and SS activity of S2, J6, EB6and SB6increased；SPS and SS activity of othertreatments of reducing source increased at the early grain filling stage and decreased at thelate grain filling stage(except SPS and SS: ZD3N3S3and XD3N3S3increased; SPS:XD3N3S4>S0).6Key enzyme activity of leaf in nitrogen metabolismGOGAT, GDH and GS activity of S2, J6, EB6and SB6increased；GOGAT, GDH andGS activity of other treatments of reducing source increased at the early grain filling stage anddecreased at the late grain filling stage(except GOGAT and GS: ZD3N3S3and ZD3N3S4increased).NR activity of S2, S3and S4in Zhengdan958increased (except NR activity of D2N0S3,ZD2N0S4, ZD1N3S3and ZD1N3S4increased at the early grain filling stage and decreased atthe late grain filling stage). NR activity of S2in Xianyu335increased (except NR activity of XD2N0S2decreased at the late grain filling stage). NR activity of S3and S4increased at theearly grain filling stage and decreased at the late grain filling stage (except NR activityXD3N3S3and XD3N3S4increased). NR activity of reducing-source-treatments at differentstage increased at the early grain filling stage and decreased at the late grain filling stage(except J6, EB6and SB6increased).7Active oxygen metabolism, membrane lipid overoxidation and soluble protein contentin maize leafSOD, POD, CAT activity and soluble protein content of S2, J6, EB6and SB6increased(except SOD, POD, CAT activity of ZD2N0S2, XD2N0S2and XD1N3S2decreased andsoluble protein content of XD1N3S2decreased at the late grain filling stage). SOD, POD,CAT activity and soluble protein content of other treatments of reducing source increased atthe early grain filling stage and decreased at the late grain filling stage (except SOD, POD,CAT activity of XD3N3S3, ZDN3S3and ZDN3S4increased and soluble protein content ofZDN3S3and ZDN3S4increased).MDA content of S2, EB6and SB6decreased (except ZD2N0S2, XD2N0S2andXD1N3S2increased at the late grain filling stage); MDA content of other treatments ofreducing source decreased at the early grain filling stage and increased at the late grain fillingstage (except ZD3N3S3<Control)..8Hormone content in maize leafIAA and GA content of reducing-source-treatments of leaf increased. ZR content of J6,EB6and SB6increased and other reducing-source-treatments of leaf decreased. ABA contentof S2, J6, EB6and SB6decreased and other reducing-source-treatments of leaf and grainincreased. IAA content of reducing-source-treatments in grain increased. GA and ZR contentof S2, J6, EB6and SB6in grain increased...