Effects Of Shading On Maize Yield And Photosynthetic Fluorescence Physiological Characteristics

Maize is widely distributed in China,and there are significant differences in light and temperature resources in different regions.Northwest China is the region with the most abundant light radiation resources in China.In this paper,different light radiation levels are created by shading to determine the photosynthetic response curves and spinning period of maize during the spinning and filling stages.Photosynthetic fluorescence parameters,analyze the effects of different light radiation conditions on maize photosynthetic fluorescence parameters and yield,reveal the response mechanism of maize leaf photosynthetic fluorescence physiological characteristics to different light radiation during spinning filling,which is the high yield and high photosynthetic efficiency of maize under different radiation conditions Cultivation provides a theoretical basis.In this study,the light-sensitive varieties Denghai 618(DH618)and Zhengdan 958(ZD958)were used as test materials,and four shade levels S0(100%light transmittance),S1(85%light transmittance),S2(Light transmittance 70%),S3(light transmittance 50%),use the Li-6400XT photosynthesis apparatus to measure the light response curve of the maize during the filling stage(30d after spinning)of different shade levels,and use FMS-2 portable pulse modulation Fluorescence instrument was used to measure the fluorescence parameters during the spinning stage.The following research conclusions are drawn:1.During the silking stage,the net photosynthetic rate(Pn),stomatal conductance(Gs),and transpiration rate(Tr)of DH618 and ZD958 maize leaves gradually increased with the increase of light intensity(PAR),but the light intensity(PAR)Greater than 1500 μmol·m-2·s-1,the net photosynthetic rate(Pn),stomatal conductance(Gs),and transpiration rate(Tr)slowed down rapidly with increasing PAR,but no photoinhibition occurred.During the grouting period,when the light intensity(PAR)is greater than 1500 μmol·m-2·S-1,the light suppression phenomenon appears under its strong light.With the increase of different shades,the net photosynthetic rate(Pn),stomatal conductance(Gs),and transpiration rate(Tr)of DH618 and ZD958 maize leaves in two periods were significantly lower than those of the control(S0)over the same period,and the differences between treatments were significant.The specific performance is:S0>S1>S2>S3,the changes of intercellular carbon dioxide concentration(Ci)and water use efficiency(WUE)are the opposite,and the intercellular carbon dioxide concentration(Ci)and water use efficiency(WUE)vary with different shade levels and The increase of light intensity was significantly increased compared with the control(S0)in the same period,and the specific change trend was S3>S2>S1>S0,and the photosynthetic parameters of the two varieties were higher during the silking stage than during the filling stage,and the photosynthetic performance of DH618 was better than ZD958.2.Under shading conditions,the maximum net photosynthetic rate(Pnmax),dark respiration rate(Rd),light compensation point(LCP),and light saturation point(LSP)of DH618 and ZD958 during the silking and filling stages all depend on the degree of shading.Increase and decrease,which in S3Under shading conditions(50%light transmittance),the effect is more significant.The initial quantum efficiency(α)is the opposite.It increases with the degree of shading.The specific change trend is S3>S2>S1>S0,and DH618 Each photosynthetic physiological parameter value is higher than ZD958.3.At the silking stage,the relative chlorophyll content(SPAD),leaf photosynthetic parameter net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr),fluorescence parameter PSII actual photochemical quantum yield of two varieties of maize(ΦPSⅡ),the maximum photochemical quantum efficiency(Fv/Fm),and the photochemical quenching coefficient(qP)all significantly decrease with the increase of the degree of shading and effective photosynthetic radiation.The light shade(S1,S2,light transmittance 85%,70%)has a larger decrease in treatment,which is specifically represented by S0>S1>S2>S3,photosynthetic parameters,intercellular carbon dioxide concentration(Ci),and fluorescence parameters.The change trend of the extinction coefficient(NPQ)is the opposite,which increases with the increase of the degree of shading,and the specific change trend is S3>S2>S1>S0.4.Shading significantly reduced the yield of maize kernels,significantly delayed the date of male tasseling and silking,physiological maturity and growth period.DH618 yields S1,S2,and S3 treatments were reduced by 8.03%,9.92%,and 97.12%compared to the control(S0),and ZD958 yield S1,S2,and S3 treatments were decreased by 14.98%,18.64%,and 94.47%compared to the control(S0).The effect of S3(50%light transmittance)treatment is more significant,and the effect of different shade treatments on the yield of DH618 is greater than ZD958.5.Under different shading conditions,the photosynthetic fluorescence parameters and yield of DH618 and ZD958 2 maize varieties had strong correlations.Except for the intercellular carbon dioxide concentration(Ci),non-photochemical quenching coefficient(NPQ)and yield of maize leaves were significantly negative Besides correlation,the remaining photosynthetic parameters and fluorescence parameters are extremely significantly positively correlated with yield.Among them,DH618 maize leaf net photosynthetic rate(Pn),intercellular carbon dioxide concentration(Ci),actual photochemical quantum yield(ΦPSⅡ)and yield have the highest correlation.ZD958 maize leaf net photosynthetic rate(Pn),intercellular carbon dioxide concentration(Ci)The maximum photochemical conversion efficiency(Fv/Fm)has the highest correlation with yield,and the yield and power of various photosynthetic fluorescence parameters change as a power function.Among them,the yield of DH618 is fitted with net photosynthetic rate(Pn)and intercellular carbon dioxide concentration(Ci).The degree of R2 is higher than 0.766.The yield of ZD958 and the maximum photochemical conversion efficiency(Fv/Fm),and the actual photochemical quantum yield of PSⅡ(ΦPSⅡ)have a high degree of fit,and their R2 are all>0.71.The main photosynthetic indicators of maize yield are net photosynthetic rate(Pn),intercellular carbon dioxide concentration(Ci),and the main fluorescent indicators affecting maize yield are maximum photochemical conversion efficiency(Fv/Fm),and actual photochemical quantum yield of PSⅡ(ΦPSⅡ).The photosynthetic fluorescence ability of maize leaves can effectively reflect the characteristics of yield changes.Under shading conditions,the decrease of maize yield is the result of the combined effects of various yield-related indicators.