Regulation Of Nitrogen Application On Source-Sink Metabolism Characteristics Of High-yielding Summer Maize

Maize (Zea mays L.) is one of the important grain crops and high-quality feeds in China. It play an significant role in ensuring food safety to research the mazie high-yielding theory. In order to research the regulation of Nitrogen application on source-sink metabolism on high-yield maize.In order to research the regulation of Nitrogen application on source-sink metabolism on high-yield maize.Five treatments were included in nitrogen fertilizer application patterns experiment, i. e. no nitrogen fertilizer, basal application in seed channel (diammonium phosphate, 300 kg/hm2, KCl, 300 kg/hm2, and urea, 750 kg/hm2), basal application in seed channel (diammonium phosphate, 300 kg/hm2 and KCl, 300 kg/hm2)+ topdressing at 9 full expansion leaves stage(urea, 750 kg/hm2), basal application in seed channel (diammonium phosphate, 300 kg/hm2 and KCl, 300 kg/hm2)+ topdressing at 6 full expansion leaves stage(urea, 300 kg/hm2) + topdressing at 12 full expansion leaves stage(urea, 450 kg/hm2), and applying controlled release nitrogen fertilizer in seed channel (N: P2O5:K2O=22:9:9, 1333 kg/hm2, urea, 232 kg/hm2, and KCl, 100.05 kg/hm2). The treatments were expressed as T0, T1, T2, T3 and T4, respectively. Four treatments were included in nitrogen fertilizer application rates experiment, i. e. 0 kg/hm2, 300 kg/hm2(urea, basal application, 323 kg/hm2 + topdressing at 12 full expansion leaves stage, 323 kg/hm2), 375 kg/hm2(urea, basal application, 323 kg/hm2 + topdressing at 12 full expansion leaves stage, 485 kg/hm2), and 375 kg/hm2(urea, basal application, 323 kg/hm2 + topdressing at 12 full expansion leaves stage, 323 kg/hm2+topdressing at silking stage, 162 kg/hm2). The treatments were expressed as N0, N1, N2, and N3, respectively. The photosynthesis characteristic, sucrose phosphate synthase (SPS), nitrate reductase (NR), and sucrose content in maize leaf were determined to study the regulative effects of nitrogen fertilizer on“source”ability. The sucrose synthase (SS), acid invertase (AI), and starch accumulative characteristic in grain were determined to study the regulative effects of nitrogen fertilizer on“sink”ability. The endogenous oxygen radicals scavenging enzymes systems and membrane lipid peroxidation were determined to study the regulative effects of nitrogen fertilizer on leaf senescence. And the effects of nitrogen fertilizer on nitrogen use and distribution were studied by using 15N tracer technique.The main results were as follows:1. Effects on summer maize population growth after nitrogen applicationThe LAI, above ground dry matter, plant and ear height, and stem diameter were increased by nitrogen fertilizer. By comparing the nitrogen fertilizer application patterns, T3 showed greatest regulative effects, followed by T4.2. Regulation of“source”assimilation applicating ability on summer maize after nitrogen applicationThe order of the chlorophyll content, Fv/Fm,?PSII, qP, photosynthetic rate, and stomatal conductance was T3>T4>T2>T1>CK, which showed T3, by compared with other nitrogen fertilizer application patterns, has the greatest positive effects on delaying leaf senescence, increasing chlorophyll content, and increasing potential activity and maximum photochemical efficiency of PS?.The light thermal dissipation was decreased and the catch and efficiency of PS?was increased by T3 treatment, which resulted more assimilate accumulated under T3.The greatest SPS activity was under T3, followed by T4, T2, T1, and CK, respectively, which suggested T3 was benefit to most sucrose accumulated in leaf and“source”ability to support assimilate. As a result, sucrose content under T3 was greatest, by compared with other nitrogen fertilizer application patterns at same stage. And under high-yield condition, with the nitrogen fertilizer application rate increasing, NR activity in ear leaf was increased when application rate between 150kg.hm-2 and 300 kg.hm-2, and then decreased when application rate beyond 400 kg.hm-2.The results suggested applying nitrogen fertilizer, especially using T3 application pattern, not only increase chlorophyll content, photochemical efficiency of PS?, and CO₂ assimilation capacity in leaf, but also increased NR activity, SPS activity, and soluble sugar content in leaf, and then increased“source”ability to support assimilate, which was beneficial to obtain maize high-yield.3. Regulatory effects on“sink”ability of summer maize after nitrogen applicationApplying nitrogen fertilizer can increase SS and AI activity in grain significantly. During grain developing period, except 45d after pollination, by comparing with CK, SS and AI activity in grain increased significant under every applying nitrogen treatment. Compared with other nitrogen application patterns, T3 treatment increased SS and AI activity in grain greatest, followed by T4. From 5d to 45d after pollination, the content of soluble sugar and starch increased while the content of sucrose and protein decreased. And during 5d¹5d after pollination, starch content increased sharply and sucrose content decrease sharply in grain, which suggested sucrose content decrease was relative to starch production. The grain filling rate, grains per ear, and yield were increased under all applying nitrogen fertilizer treatments, especially under T3 treatment.4. Effects on nitrogen distribution and utilization of summer mazie in different nitrogen application approachesThe effects of nitrogen fertilizer application rates on nitrogen using and distribution in summer maize under high- and middle-yield conditions were determined. The results showed the order of nitrogen uptake, distribution ratio, and use efficiency was same: grain>leaf>stem>root. Under high-yield condition, with nitrogen fertilizer application rate increased, nitrogen uptake by plant and grain was increased first, and then decreased, and the peak occurred under HM treatment. But under middle- yield condition, they increased with nitrogen fertilizer application rate and the peak occurred under MH treatment. The nitrogen uptake by stem increased and nitrogen use efficiency decreased with nitrogen fertilizer application rate under two yield conditions. Based on the results, taken yield, nitrogen use efficiency, nutrition transport, and environmental pollution into account, the recommended nitrogen application rate was under 300kg.hm-2 in high-yielding field and 300?400 kg.hm^-2 in general-yielding field.5. Indicated the pattens of high-yield summer maize source-sink metabolism and high-yield mecaniques after nitrogen application Select high-yield maize variety and apply nitrogen fertilizer scientific can regulate“source”and“sink”activity, and increase the“source”support ability and“sink”storage ability, which result the high-yield and efficiency maize production.