Response Mechanism Of Stem And Leaf Organs To Yield Formation In Maize-soybean And Maize-peanut Multiple Intercropping Under Different Nitrogen Levels

Gramineae-Leguminosae intercropping systems have potential yield advantages.The maize-soybean relay intercropping and maize-peanut strip intercropping are two kinds of compound planting patterns that are currently widely applied.To explore the response mechanism of crops dry matter production,nitrogen(N)accumulation and stem and leaf characteristics on yield formation in maize-soybean and maize-peanut intercropping systems.The field experiment was designed by a two-factor split-plot with the main plots was four N application levels,including zero N(ZN),lower N(LN),standard N(SN),higher N(HN),and the sub-plots was five planting patterns,including maize monoculture(MM),soybean monoculture(MS),maize-soybean relay intercropping(IMS),peanut monoculture(MP)and maize-peanut strip intercropping(IMP).Analyzed the effect of the stem and leaf characteristics,biomass production and N accumulation on yield formation of crops.Aiming at revealing the response mechanism of the stem and leaf organs on the yield formation of the crops in the maize-soybean and maize-peanut intercropping systems.Results are as follows:1.Compared with MM,IMS increased the chloroplast volume and thickened the grana lamella stack of maize leaves.The net photosynthetic rate,chlorophyll content and leaf area of maize in IMS were increased by 13.9 %,8.9 %,11.3 % compared with MM,respectively.The stem diameter of intercropped maize was increased.Compared with MM,the stalk injury flow,soluble sugar,nitrate N,and inorganic phosphorus concentrations in the wound fluid components of intercropped maize both increased by 35.6 %,19.6 %,85.1 % and 44.7 %,respectively.In IMS,the source increase of maize leaf and the fluid increase of stem increased the biomass and N accumulation by 44.7 % and 42.2 %,which increased the grain number of maize by 40.2%.Compared with MS,in the symbiotic period,the net photosynthetic rate and leaf area of soybean in IMS were decreased by 8.7 % and 11.9 %,respectively,while the chlorophyll content of IMS was increased by 6.2 %.The stem diameter and xylem thickness of intercropped soybean were decreased,but the thickness of the xylem was increased.Therefore,the wound fluid of intercropped soybean decreased by 62.3 %.In the late symbiotic period,the leaf area of intercropped soybean was increased by 18.2 %,whereas the chlorophyll content was decreased by 8.6 % compared with MS.The improvement of leaves and stems after symbiosis increased intercropped soybean biomass and N accumulation by 23.1 % and 25.3 %,so that increased the number of grain per plant by 25.3 %,respectively.Indicating that the increased system yield of maize-soybean intercropping resulted from the joint increased of maize grain number per panicle and soybean grain number per plant.2.Compared with MM,IMS increased the chloroplast volume and thickened the grana lamella stack of maize leaves.The net photosynthetic rate,chlorophyll content and leaf area of maize in IMS were increased by 4.6 %,7.4 %,14,6 % compared with MM,respectively.The stem diameter of intercropped maize was increased.Compared with MM,the stalk injury flow,soluble sugar,nitrate N and inorganic phosphorus concentrations in the wound fluid components of intercropped maize both increased by 45.9 %,38.3 %,91.1 % and 47.3 %,respectively.In IMS,the source increase of maize leaf and the fluid increase of stem increased the biomass and N accumulation by 53.0 % and 427.3 %,which increased the grain number of maize by 41.2 %.Compared with MP,in the symbiotic period,the leaf area of peanut in IMP was decreased by 39.9 %,while the chlorophyll content of IMP was increased by 13.5 %.The stem diameter and the thickness of xylem and phloem in IMP both were decreased.In the late symbiotic period,the chloroplast grana lamella stack of intercropped peanut was thickened,and starch granules are accumulated.Although the leaf area of intercropped peanut was decreased by 34.3 %,the chlorophyll content was increased by 9.4 % compared with MS.There was a recovery growth on the stem of intercropped peanut.The reduced source and sink of intercropped peanut in IMP decreased the dry matter,N accumulation and the number of peanuts per plant by 43.6% 37.4%,and 51.0%,respectively.This indicates that the increase of maize kernel number could make up for the reduction of the number of peanuts per plant and achieve stable system production of maize-peanut intercropping mode.3.The IMP promotes maize growth more than IMS.Compared with IMS,the grana lamella stack of IMP was decreased,as well as,the chlorophyll content and the net photosynthetic rate was decreased by 1.4% and 8.1%,respectively.Whereas,the leaf area,the wound fluid including soluble sugar,nitrate N and inorganic phosphorus concentration of IMP both were higher than IMS by 2.9 %,13.0 %,15.6%,3.2%,and 6.3%,respectively.The maize dry matters,N accumulation,grain number per panicle,and yield in IMP was increased by 5.7 %、3.6 %、0.6 %,and 3.1 % compared with IMS,respectively.Indicating that the IMP had a stronger capacity on source and sink of maize than IMS.4.Nitrogen application could promote the growth of crops,but excessive N application will have a disadvantageous effect on crops.In this study,SN was the most suitable N application rate for the growth of crops.Compared with ZN,the yield,dry matters and N accumulation of maize,soybean and peanut of SN were both increased by 10.1 %,24.8 %,23.6 %;16.9 %,15.2 %,15.5 %;and 18.1 %,29.9 %,41.5 %,respectively.Applied N thickened the crops stem diameter,therefore,the wound fluid of maize and soybean was increased by 14.0% and 47.8%,respectively.Maize and soybean leaf area increased by 12.3% and 29.4% respectively.The growth of peanut leaf area was regulated by N fertilizer.