A Study On Characteristics Of Radiation And Photosynthesis In Canopy Of Super High-yield Summer Maize

Maize is an important grain crop in northern China, and its productionlevel closely related with the food security. Because individual maise productionability is larger, and self-adjustment ability is weak, increase of the planting density isan important way to reach higher output. However, if the planting density exceedsappropriate range, contradiction between the individual growth and populationdevelopment becomes prominent. It mainly because the canopy in the field is closure,ventilation and the pervious light is bad, and the light in the environment of thecanopy become deteriorated, then the leaves cause stressed by the weak light,resulting in photosynthetic performance down, and the leaves accelerate ageing,source metabolism disorders, in the end short of increasing yield. This project studiedthe effects of density, planting mode and variety on photosynthetic characteristics,aging process and source metabolism. The main results are as follows:1. Studies on characteristics of radiation in canopy of super high-yield summermaizeUnder different varieties and plant modes, light transmittance decrease with theincrease of plant density, which is the opposite of the leaf area index. In the earlierstage, zhengdan958’s light transmittance is higher than Xundan20, but lower thanxundan20in silking stage. There exists significant differences. The influence ofplanting mode on the transmittance rate is not obvious, almost no significantdifference. Look From the top layer, the layer of ear leaf to bottom layer on differentcanopies, light transmittances are in significant difference of5%level. That improvesthe canopy of summer maize at the bottom has great potential of the light intensity,especially improve the light intensity of the layer below the ear leaf. It shows in thetable that there is the1%significant level very significant between the top lighttransmittance and the ear layer which has no especially significant difference with theground of canopy. But if you want to avoid the loss of the top canopy, lighttransmittance should be reduced.2. Studies on photosynthetic characteristics in canopy of super high-yield summermaizeFv/Fm, qP, NPQ in the third leaf above ear is higher than the ear leaf and the third leaf below ear. And two summer maize under different densities, Fv/Fm, qP, NPQdecrease as density increases. In different stages, Fv/Fm, qP, NPQ were highest insilking stage, declined in grain-filling stage and picked up in maturing stage.Zhengdan958and wide-narrow row planting method were superior than Xundan20and equidistant row planting method in two varieties of chlorophyll content. And itdecreased with the increase of the density. With the best yield of the results, we cansee the optimal population density is82500/hm~2.3. Studies on index of growth and development of super high-yield summer maizeThe leaf area index (LAI), dry matter accumulation of the two varieties increasewith the increase of density. Plant height in these treatments decrease with theincrease of density. With developing of stages, stem diameter increased first and thendecreased. It reached maximum in silking stage. Stem diameters decreased withdensity increasing..4. Studies on protein, carbohydrate content of Super High-yield Summer MaizeThe third leaf above ear and the ear leaf were higher with sugar and protein contentthan the third leaf below ear. That showed the third leaf above ear and the ear leaveswere in key position for demand and synthesis of sugar and protein. With the plantingdensity increased, sugar and protein content were become lower. Xundan20’s sugarand protein content were general higher than Zhengdan958. When the plant densitygot to82500/hm~2, soluble sugar content and protein content are all reached themaximal. With the best yield of the results, we can reckon that the optimal populationdensity was82500/hm~2, which explained that the community density at82500/hm~2planting was good for the leaf of maize accumulating more soluble sugar in earlygrow stages and transferring to the grain in later grow stages.5. Protective enzymes and lipid peroxidation level of super high-yield summerMaize during the aging processIn the situation of density for82500/hm~2,the leaves show higher SOD and PODactivity and lower MDA content, which shows that the planting patterns of the densityfor82500/hm~2are more conducive to enhance the scavenging of reactive oxygenspecies of mesophyll cells, effectively control membrane lipid peroxidation level,maximally maintain cell membrane stability, thereby improving the ability ofanti-adversity of corns, slowing the aging of the corn, and lay the foundation for highyield.6. The yield of super high-yield summer maize The production of Zhengdan958in these treatments increased with increasingdensity, while the production of Xundan20first increased and then decreased withincreasing density. The production of Zhengdan958is higher than Xundan20，equalline spacing is slightly higher than the wide-narrow planting, but not obvious. Thegrain number of two varieties in the B3(82500/hm~2) both reaches a good level. Thedifference of thousand-grain weight not significant, Zhengdan958is slightly higherthan Xundan20. Zhengdan958is overall better than Xundan20in the yield, the densityin B3, B4can reach to more than10000kg/hm~2. Zhengdan958at82500-90000/hm~2and Xundan20at82500/hm~2, which in this density, the characteristics of radiation andphotosynthesis were more reasonable, the population and individual development aremore coordinated, and the yield is the best.