| The canopy architecture, solar radiation traits and apparent photosynthesis characteristics of both small spike-type cultivar(Yumai 49) and large spike-type cultivar(Zhoumai 13) had been studied under field conditions. The main results were as follows:1. The Leaf Area Index(LAI) of both the cultivars showed as a single-peaked curve and the peak value reached at anthesis. With the increasing of density, the LAI of all treatments enhanced before anthesis. The B2 and B4 treatments had longer green leaf area duration after anthesis. The LAI of Yumai49 were higher than that of Zhoumai 13 at the same stage. The leaf distribution of the 62 of the two cultivars were more reasonable than that of the others. With the wheat growing, the Mean Leaf Angle(MFIA) of the two cultivars decreased gradually. The higher density treatments had smaller MFIA than the lower density treatments. The differences of MFIA among the treatments after booting stage were larger than that of the stage before reviving. The MFIA of Zhoumai 13 at waxening stage were greater than Middle-filling stage. The Extinction Coefficant(K) of both the cultivars enlarged with increasing of zenith angle. Treatments B2 of both cultivars had a reasonable canopy architecture than others, which accounted for they had intercepted more solar63radiation. The Transmition Coefficient for Radiation Penetration(TR) for the two cultivars at anthesis and middle-filling stage declined with increasing of zenith angle. There were significant differences among all of the treatments at anthesis, but the differences were smaller at middle-filling stage. For the two spike-type cultivars, the B2 treatments were the best.2. There were the same trends in the change of canopy apparent photosynthesis (CAP) rate in both small spike-type cultivar and large spike-type cultivar. During wheat development, the CAP generally appeared as a single-peaked curve and the peak value reached at anthesis. Yumai 49 had a higher CAP before booting stage, but Zhoumai 13 showed obvious dominance in CAP after flowering stage. The change of CAP in canopy leaf source capacity(CLSC) of the two cultivars was similar to that of CAP. The diurnal changes of CAP at flowering stage and mid-filling stage were single-peaked ones and the peak value appeared at 10am. The differences existed in the CAP among different planting densities of the two cultivars.3.There were identical trends in the changes of net photosynthesis(Pn) rate and RUBPcase activity of flag leaf for both cultivars. At the beginning of spreading of flag leaves for both cultivars, their Pn and RUBPcase activity inclined gradually, and reached the max at the tenth day after spreading, then declined little by little. Compared with Zhoumai 13, Yumai49 had higher Pn and RUBPcase activity from the Oth to the 10th day after spreading of flag leaf. But there was contrary fact after 20 days. The B2 treatment of the two cultivars had apparent advantages in Pn, RUBPcase activity, carboxylation efficiency and Chi content of flag leaf.644. The diurnal changes of flag leaf net photosynthetic rate (Pn) for the two cultivars and its major affecting factors, i.e. Leaf Temperature (TL), Photosynthetically Active Radiation (PAR), Transpiration rate (Tr), Stomatal Conductance (Gs) and Intercellar CO2 Concentration (Ci) were tested. The results indicated that both cultivars showed midday depression phenomenon at anthesis. The Pn of Yumai49 varied as a two-peaked curve, whose peak values appeared at 10h and 14h, but Zhoumai13 varied as a single-peaked curve with peak value appeared at 10h. Both cultivars showed serious midday depression phenomenon at middle-filling. The relation between flag leaf net photosynthetic rate and its affecting factors was analysed by the correlation analysis and path analysis. At anthesis, the Pn of Yumai49 at 8h,10h,12h and 14h were influenced mainly by stomatal factors, but at 16h and 18h, non-stomatal factors played an important role. The Pn of Zhoumail3 were limited by Stomatal factors at 8h,10h,14h and... |
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