| Taking Zhongdan 909 as the material,the combination of different concentrations of 5-aminolevulinic acid(5-ALA)and ethephon(ETH)were used to spray on the leaves of maize at the jointing stage(V6),and then applied to Gongzhuling Experimental Station in Jilin Province from 2018 to 2019,the effects of different combinations of 5-ALA and ETH on chlorophyll content of functional leaves,photosynthetic characteristics of leaves,activities of key enzymes involved in carbon metabolism of source-sink,accumulation and distribution of dry matter,grain filling characteristics and yield of spring maize were studied,the regulation mechanism of 5-ALA and ETH on chilling injury and light deficiency during the growing period of spring maize in northeast China was studied,it provides theoretical basis and technical support for establishing chemical control cultivation techniques of cold-resistant,dense-tolerant and stable yield of spring maize in northeast China and ensuring its high and stable yield.The main findings are as follows:1.Compared with single-dose treatment and other treatments,compound treatment of 5-ALA(22.5 g·hm-2)and ETH(450 mL·hm-2)prolonged the effect time of 5-ALA and increased the chlorophyll content of functional leaves during the growth period.Before silking,the total chlorophyll content of functional leaves increased significantly by 8.9%compared with the control in the vegetative 7th leaf(V7)stage,the functional leaf of chlorophyll b/chlorophyll a(Chlb/Chla)increased by 3.0%on average from V7 to vegetative 9th leaf(V9)stage,and enhanced the light catching ability of the functional leaf;after the silking stage,the total chlorophyll content of the functional leaves increased significantly by 17.4%and 11.3%compared with the control on the 30th and 40th day after silking(30 DAS and 40 DAS),respectively,the SPAD value of the functional leaves increased significantly by 8.3%on the 50th day after silking(50 DAS),and the LAI of 30 to 60 DAS increased by 3.2%on average compared with the control,which delayed the senescence of the leaves at the late stage of grain filling.2.The combination of 5-ALA(22.5 g·hm-2)and ETH(450 mL·hm-2)increased the activity of key enzymes in functional leaves of maize from trumpet stage(V12)to silking satge(VT),and the activity of RuBP carboxylase(RuBPCase)of functional leaves in V12 and VT stage were 65.2%and 79.5%higher than that of control,respectively,the activity of PEP carboxylase at V12 stage was 87.1%higher than that of control,and the effect on photosynthetic enzyme activity was better than that of single-dose treatment.3.The combination of 5-ALA(22.5 g·hm-2)and ETH(450 mL·hm-2)improved the photosynthetic performance of functional leaves during the growth period.Before silking,the net photosynthetic rate(Pn),stomatal conductance(Gs)and transpiration rate(Tr)of functional leaves at vegetative 8th leaf(V8)and V12 stage were significantly increased by 14.8%and 24.5%,23.1%and 76.5%,and 38.2%,respectively,the intercellular CO2 concentration(Ci)in functional leaves of V12 stage was 46.3%higher than that of control;after the silking stage,the Pn of functional leaves increased by 1.8%and 4.9%compared with the control in 40 DAS and 50 DAS,respectively,and the Gs,Ci and Tr of functional leaves increased by 26.9%,17.5%and 15.8%compared with the control in VT stage,respectively.4.The combination of 5-ALA(22.5 g·hm-2)and ETH(450 mL·hm-2)increased the activity of sucrose phosphate synthase(SPS)in functional leaves during the growth period,before silking,the SPS activity and sucrose content of V12 functional leaves were increased by 38.4%and 15.5%,respectively,which promoted the synthesis of sucrose and the source strength of functional leaves;after the silking stage,the content of sucrose in functional leaves decreased by 14.4%in 0～20 DAS,and the content of sucrose in kernel of 10 DAS and 20 DAS increased by 60.0%and 23.1%respectively,the activities of sucrose synthase(SS)in 10～20 DAS were increased by 12.5%,acid invertase(AI)and neutral invertase(NI)by 52.8%and 24.1%,respectively,the sucrose was transported and degraded from the source to sink,and the activity of the kernel bank was enhanced.5.The combination of 5-ALA(22.5 g·hm-2)and ETH(450 mL·hm-2)reduced plant height and spike height,and promoted dry matter accumulation after silking.Before silking,the length of basal internode 4th in V12 and VT stage was 23.5%and 37,5%shorter than that in control,and the crushing strength of basal internode 4th in V12 stage was 37.8%,the length of basal intemode 5th was 19.0%and 26.2%in V12 and VT stage shorter than that of the control,and the bending resistance of the 5th internode was 41.4%and 20.6%higher than that of the control,which enhanced the strength of Basal internodes before silking;after the silking stage,the dry matter accumulation in 2018 and 2019 increased by 12.8%and 10.1%,respectively,and reached significant levels in 2018.6.The combination of 5-ALA(22.5 g·hm-2)and ETH(450 mL·hm-2)improved the initial growth potential of grain filling,promoted the filling and increased the yield.Before silking,the filling rate of 10～30 DAS was 4.9%in 2018 higher than that of the control,the ultimate grain growth(a)was 1.5%higher than that of the control,and the active filling time(p)was 8.6%longer than that of the control in 2019,and the ear length increased by 4.7%and 5.1%,the kernel number increased by 8.6%and 6.2%,the bare tip length decreased by 58.3%and 50.4%,and the yield increased by 4.8%and 5.4%compared with the control in 2018 and 2019,respectively.In conclusion,the mixture of 5-ALA and ETH could form a stable complex.A2E1 treatment(5-ALA-22.5 g·hm-2+ETH-450 mL·hm-2)increased chlorophyll content and photosynthetic enzyme activity,enhanced photosynthetic performance of functional leaves,accelerated dry matter accumulation after silking,and promoted transportation and degradation of photosynthetic products from source to sink of kernel,the grain filling was accelerated and the yield was increased significantly. |
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