| The central Jiangsu region belongs to the wheat planting belt of the middle and lower reaches of the Yangtze River,where the natural conditions of light,temperature,and water are superior.Due to the unique ecological environment and natural disasters in this area used the rice-wheat rotation,the yield stability of wheat planted after rice is poor.At present,it is difficult to increasingly improve the leaf area index and economic coefficient of crops.In order to further improve the yield of crops by increasing biomass,the key is how to improve the light utilization efficiency.The formation of crop yield is the embodiment of comprehensive photosynthetic capacity in a certain space and a certain time.Therefore,the improvement of photosynthetic capacity not only depends on the transformation of leaf,plant physiological function,and structure but also considered population development from a macro perspective This requires the culturists to focus on the actual agricultural production and carry out the regulation of the high photosynthetic efficiency population.The regulation at the population level is mainly the cultivation management,involving the reasonable close planting,timely sealing,fertilizer and water regulation,etc.This experiment took ’Yangmai 23’ and’Yangfumai 4’ as materials,which are widely used in the local production and have good comprehensive performance,and constructed different wheat populations through planting density,nitrogen application amount,and nitrogen management under the field condition in the central Jiangsu region.The present study analyzed the relationships between the characteristic indexes of population light utilization and grain yield,compared the differences in the photosynthetic matter production and transportation,photosynthetic physiology,nitrogen accumulation,yield,and yield composition between/among different types of wheat populations,explored the establishment of wheat population characteristic system with high photosynthetic efficiency,and propose the key cultivation techniques and measures for the construction of high photosynthetic efficiency population.The results were expected to provide theoretical and technical support for the construction of high photosynthetic efficiency wheat population in the central Jiangsu region.The main results were as follows1.The grain yield,spike number,and 1000-grains weight of high photosynthetic efficiency population(HPEP)of Yangmai 23 and Yangfumai 4 were significantly higher than those of medium and low photo synthetic efficiency population(MPEP and LPEP).The HPEP of the two varieties had more grains per spike,with significantly or not significantly different from that of MPEP and LPEP.The results showed that based on enough spikes,the HPEP could gain high yield by increasing the weight of a single spike,especially 1000-grain weight2.Compared with MPEP and LPEP,HPEP of two wheat varieties showed significantly greater high-efficiency leaf area ratio at anthesis stage,dry matter accumulation after anthesis,biomass,and harvest index.The improvement of economic yield depended on the synergistic improvement of biological yield and harvest index.The photosynthetic potential of HPEP was significantly higher than that of LPEP at all growth stages,but the pre-anthesis photo synthetic potential of HPEP of Yangmai 23 did not show a significant advantage.The results indicated that the photosynthetic advantage of HPEP was more significant after anthesis,and its dry matter accumulation after anthesis contributed a lot to the wheat yield.The correlation of high-efficiency leaf area rate at anthesis stage with the photosynthetic potential after anthesis,dry matter accumulation after anthesis,and 1000-grains weight reached a significant level,which indicates that improving the high-efficiency leaf area rate of the population at anthesis stage was beneficial to enhancing the photosynthetic production capacity and promoting the production and transportation of photosynthetic matter after anthesis3.The stem and tiller number and leaf area index of HPEP of Yangmai 23 at overwintering and jointing stage were significantly higher than that of LPEP;compared with MPEP,HPEP was significantly lower or not significantly different.At the same growth stage,the stem and tiller number and leaf area index of HPEP were significantly higher than those of MPEP and LPEP.The stem and tiller number and leaf area index of the two wheat varieties with high photosynthetic efficiency after anthesis were superior to those with medium and low photosynthetic efficiency.The results also showed that the HPEP maintained relatively stable and high tiller number and leaf area index before the booting stage.The tiller number and leaf area index at anthesis stage were significantly higher than those of MPEP and LPEP,the leaf area decreased slo wly after anthesis,and maintained a significantly higher leaf area index until milk-ripening stage with a long effective photosynthetic duration.In addition,the earing percentage of stem and tillers of HPEP was significantly higher than that of MPEP and LPEP4.Compared with the MPEP and LPEP,the HPEP had a relatively small light transmittance,indicating that the HPEP had a higher light interception rate and less light leakage loss.At the same time,the flag leaf of HPEP had significantly higher SPAD value and the maximum photochemical efficiency and could maintain stable and higher SPAD value,net photosynthetic rate,and the maximum photochemical efficiency after anthesis.The SPAD value of flag leaf reached the peak value lately(on 14 days after anthesis)and decreased slowly during the late period,which was beneficial to delaying leaf senescence,prolonging leaf function period,and promoting photosynthetic material production5.Compared with the LPEP,the nitrogen accumulation of the HPEP was significantly higher at each growth stage.Compared with the MPEP,the nitrogen accumulation from seedling emergence to overwintering stage of Yangmai 23 population with high photosynthetic efficiency was significantly lower.There was no significant difference between HPEP and MPEP in the nitrogen accumulation from jointing to the booting stage of Yangfumai 4.The nitrogen accumulation after anthesis and the nitrogen content per unit area of flag leaf showed HPEP>MPEP>LPEP,with significant differences between them.The results showed that the HPEP had relatively stable and high nitrogen accumulation at the early growth stage with a significant advantage after anthesis.There was a significant positive correlation between flag leaf N content per unit area and flag leaf net photosynthetic rate,maximum photochemical efficiency,and 1000-grains weight,which indicated that higher N content of flag leaf at the flowering stage was beneficial to improving the photosynthetic performance of wheat population at the grain-filling stage and promoting grain filling.6.Planting density,nitrogen application,and nitrogen management had significant regulatory effects on the yield components and population light utilization index of Yangmai 23 and Yangfumai 4.With the increase of planting density(from 150×104·hm-2 to 300×104·hm-2),the number of population,the number of spikes,dry matter accumulation after anthesis,and biomass were significantly increased,while the leaf area per unit area was increased,the gap between populations was decreased,and the light transmittance was decreased significantly.Increasing nitrogen application properly(from 210 kg·hm-2 to 270 kg·hm-2 or 330 kg·hm-2)met the demand of nitrogen nutrition for the large population.Besides,the growth of population was vigorous,and the increase of leaf area index led to the increase of light interception rate and the decrease of light transmittance,while the photosynthetic efficiency of leaves was increased,the duration of photosynthetic function of green leaves was prolonged,population growth and material accumulation were increased,grain filling was promoted,and grain weight per spike was effectively increased.The nitrogen fertilizer application at a late stage(5:1:2:2 compared with 7:1:2:0)could not only ensure enough spikes but also help the plant maintain higher nitrogen nutrition and photosynthetic production capacity at the late growth stage.It also coordinated the development of spikes and 1000-grains weight,thus improving the grain yield.7.Under the experimental condition of the high rainfall at post-sowing and in the winter,a management combination constructing HPEP of wheat planted after rice in the central Jiangsu region was initially formed.This combination,achieving the yield potential of 8300 kg·hm-2 with ’Yangmai 23’,included planting density of 225×104·hm-2,nitrogen rate of 270 or 300 kg·hm-2,and nitrogen management 7:1:2:0,or planting density of 300×104·hm-2,nitrogen rate of 270 or 300 kg·hm-2,and nitrogen fertilizer management 5:1:2:2.In addition,the combination,achieving the yield potential of 8000 kg·hm-2 with‘Yangfumai 4’,included planting density of 150×104·hm-2,nitrogen rate of 330 kg·hm-2,and nitrogen fertilizer management 5:1:2:2,or planting density of 300×104·hm-2 nitrogen rate of 330 kg·hm-2,and nitrogen fertilizer management 7:1:2:0. |
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