| Hydroponic culture experiment of different oxygen concentrations in rhizosphere and fieldexperiment of different aerobic irrigation modes were conducted to compare the effects of oxygenconcentrations in rhizosphere on growths and activities in roots of different rice cultivars, and to studythe relationship between oxygen concentration and nutrient uptake and grain yield of rice cultivars.IR45765-3B (deepwater rice cultivar), Zhonghan221(upland rice cultivar) and Zhongzheyou1(lowland rice cultivar) were used in hydroponic culture experiment, Xiushui09(inbred japonica rice),Guodao6(indica hybrid)and Liangyoupeijiu(indica hybrid) were used in field experiment. Oxygenconcentrations in rhizosphere in hydroponic culture experiment were regulated by on-line controller ofdissolved oxygen. Aerobic irrigation modes in field experiment were comparative tests about aeratedirrigation mode by super-micro bubble water and common irrigation mode. The results in this trial couldlay foundation for high-yield cultivation technique and high yield theory relating to regulation ofoxygen in rhizosphere of rice. The main conclusions in this study are as follows:1. The maximum root length for IR45765-3B, Zhonghan221and Zhongzheyou1was increasedwith the increase of oxygen concentration in rhizosphere. The responses of adventitious roots per plant,dry weight of root, TTC deoxidizing ability in root and active absorption area of root to oxygenconcentrations in rhizosphere were varied in varieties. The above indicators for IR45765-3B got thehighest values at the oxygen concentration of4mg/l in rhizosphere, followed by2mg/l, CK and6mg/l,and the above indicators for IR45765-3B got the lowest values at the oxygen concentration of8mg/l inrhizosphere. The indicators relating to root in Zhonghan221were increased with the increase of oxygenconcentration in rhizosphere. That was to say, indicators relating to root in Zhonghan221were up to thehighest values at8mg/l of oxygen concentration in rhizosphere, followed by6mg/L,4mg/l,2mg/L,and CK. The indicators relating to root in Zhongzheyou1tended to rise with the increase of oxygen inrhizosphere, and generally peaked at the concentration of6mg/l, and decreased when the oxygenconcentration in rhizosphere was up to8mg/l.2. The responses of photosynthetic characteristics in rice flag leaf at full heading stage and agingprocess in rice flag leaf at grain filling stage were varied with varieties. The net photosynthetic rate inflag leaf for IR45765-3B, Zhonghan221and Zhongzheyou1at full heading stage got the highest valuesat4mg/l,8mg/l and6mg/l of oxygen concentration in rhizosphere, respectively. The highest value ofnet photosynthetic rate in flag leaf for IR45765-3B, Zhonghan221and Zhongzheyou1was22.4,25.6and29.3μmol·m-2s-1, respectively; the corresponding values were increased by10.3%,29.3%and13.1%compared with CK, respectively. The variations in the chlorophyll content, soluble protein,soluble sugar, MDA and SOD activity were consistent with net photosynthetic rate in the flag leafwithin21days after flowering, and the variations were small with the growth of plants.3. Grain yield per plant for IR45765-3B, Zhonghan221and Zhongzheyou1got the highest valueat4mg/l,8mg/l and6mg/l of oxygen concentration in rhizosphere, respectively; the highest value was29.0,27.2and36.6g/plant, respectively. The above highest value was increased by18.4%,61.8%and 46.3%in comparison with CK, respectively. The adventitious roots per plant (X1) and root volume (X3)at full heading stage were main characters affecting grain yield, and the regression equation was y=7.602+0.029X1+0.431X3.4. There were significant differences in the absorptive characteristics of nitrogen and phosphorousamong varieties. The nitrogen absorption efficiency and phosphorous absorption efficiency forIR45765-3B and Zhongzheyou1got the highest value at4mg/l and6mg/l of oxygen concentration inrhizosphere, respectively. However, nitrogen absorption efficiency and phosphorous absorptionefficiency for Zhonghan221got the highest value at8mg/l and6mg/l of oxygen concentration inrhizosphere, respectively. The adventitious roots per plant (X1) and root dry weight (X4) at full headingstage were main characters affecting nitrogen accumulation of rice plant, and the regression equationwas y=0.020+0.001X1+0.091X3. Root length of adventitious roots per plant (X2) and root dry weightper plant (X4) at full heading stage were main characters affecting phosphorous accumulation of riceplant, and the regression equation was y=0.009+0.002X2+0.021X4.5. In field experiment, the effective tillers for Xiushui09, Guodao6and Liangyoupeijiu insuper-micro bubble water treatment were significantly increased compared to common irrigation mode.Effective panicles for Xiushui09, Guodao6and Liangyoupeijiu in super-micro bubble water treatmentwere increased by12.1%,6.0%, and6.7%, respectively. The photosynthetic capacities in flag leaf ofabove three cultivars at full heading stage were enhanced compared to control, and treatment withsuper-micro bubble water delayed the senescence of leaves at rice grain filling stage. Then the settingpercentage for Xiushui09, Guodao6and Liangyoupeijiu was increased by5.9%,5.7%, and6.4%comparing with control, respectively, and the grain yield for Xiushui09, Guodao6and Liangyoupeijiuwas increased by7.3%,9.3%, and7.5%comparing with control, respectively... |
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