Studies On The Photosynthetic Characteristics During Grain Filling Stage In Maize Hybridizations With Different Plant-types

Based on the field experiment, the population structure, population light reception and their effects on photosynthesis of different leaf positions during grain filling stage had been studied using maize hybridizations with different plant-types, including Gaoyou 115, Nongda 108 and Zhengdan 958 representing plant-type of flat, semi-flat and erectophile, respectively. The results were as follow:1 The parameters of population structure characteristics including angle between stem and leaf, leaf orientation value, leaf upward stem property and leaf area index (LAI) in the hybridizations with different plant-type were studied. Among different hybridizations, Zhengdan958 had the lowest values of the angle between leaf and stem, the highest leaf orientation values in the leaves above the ear leaf, and the leaf upward stem propertys of Zhengdan 958 was above Gaoyou 115 and Nongda 108;LAI of Gaoyou115 rised slowly when the planting density exceeded 71,250 plant/hm2. The densities of Zhengdan 958 and Nongda108 were above the Gaoyou115 when the LAI of Zhengdan 958 and Nongdal08 were the largest. With the rising of planting densities, leaf orientation values and angles between stem and leaf reduced, while leaf upward stem property and LAI increased in the hybridizations with different plant-type.2 The analysis of LAI in different population showed the proportion of LAI of the ear leaf group was above grain leaf group and stem leaf group. Among different hybridizations, Gaoyou 115 was the largest, Nongda108 was second, Zhengda 958 was the lowest at LAI of the ear leaf group; the difference of LAI at the grain leaf group was less among the hybridizations with different plant-type; LAI at the stem leaf group in Zhengdan958 was above Nongda108 and Gaoyou115 was the last. It indicated erectophile maize could increase the number of spikes by increasing the planting density and improving photosynthetic LAI, and realized high yield at last3 The PAR diurnal change over population and within population was low in the morning and evening, while it was high at noon during grain filling stage in the hybridizations with different plant-type. Comparing the penetration rate and PAR at middle part or underlayer of population among different hybridizations with different plant-type, zhengdan958 was the highest, the next wasNongda108 and Gaoyoul 15 was the last. PAR in the hybridizations with different plant-type reduced with the rising of planting densities. But under the high density (71,250 plant/hm2), PAR at middle part and underlayer of population in Zhengdan958 were higher than Nongda108 and Gaoyoul115 obviously. Because Zhengdan958 was erectophile, which had PAR with high penetration rate , light intercept and capture amount at middle part and underlayer of population during the metaphase and anaphase stage.This was a important physiological base to plant under high density.4 The extinction coefficient diurnal change presents single apex curve: high in the morning and evening, low at noon downward; the extinction coefficient increased with the rising of planting density. Different population had different extinction coefficient exhibition among the hybridizations with different plant-type. The extinction coefficient at the upside in Gaoyoul 15 was higher than Nongda108 and Zhengdan958 in the morning; the extinction coefficient at the underlayer in Gaoyoul 15 was lower than Nongdal08 and Zhengdan958 in the morning. The difference of extinction coefficient at the underlayer population was less in the morning and evening among the hybridizations with different plant-type.5 The Pn diurnal change was single apex curve among the hybridizations with different plant-type, it didn't appear the "siesta" phenomenon. Under the high density (71,250 plant/hm2),Pn in different population increased from the upside part to the underlayer. Comparing Pn of hybridizations with different plant-type, it showed that Zhengdan958 was the highest and Nongda108 was higher than Gaoyoul 15. With the rising of planting density, Pn at the different part increased among the hybridizations with different plant-type. Under the high density, Zhengdan958 could still make the light distribute rationally in the population.6 The most Pn of the single leaf showed Nongda108 was the highest, secondly was Zhengdan958 and the lowest was Gaoyoul 15 among the hybridizations with different plant-type. The order of apparent quantum yield was Zhengdan95, Nongda108, Gaoyoul 15 with different leaf position. Following the rising of the leaf position, the dark respiration rate ascended within the hybridizations with different plant-type. The transpiration, vapor pressure deficiency on the leaf surface and gas stoma enhanced with the rising of PAR, while relative humidity had reverse tendency.7 The chlorophyll content in the different leaf position represented middle part>upside>underlayer among the hybridizations with different plant-type. The chlorophyll content fell ceaselessly with the rising of planting density among the hybridizations with different plant-type. The relativity analysis indicated, there was no correlation between Pn and chlorophyll content at the different leaf position under different density among the hybridizations with different plant-type.8 The specific leaf weight at different leaf position represented upside leaf>middle part leaf>underlayer leaf among the hybridizations with different plant-type. Along with the rising of planting density, the specific leaf weight at different leaf position was down. There was remarkable positive correlation between specific leaf weight and Pn among the hybridizations with different plant-type.9 Under the same density, the yield was increased according to Zhengdan958, Nongda108 and...