Impacts Of Solar Radiation Changes Caused By Haze On Rice Nitrogen Absorption And Partitioning

The proportion of days mild and over haze occurring was 25.3%during the whole rice growing season in 2014.The increacingly frequent haze decreased the amount of radiation reaching the surface and increases the fraction of diffuse radiation,which will affect the crop nitrogen absorption and partitioning,thereby affecting the photosynthetic production.In order to ascertain the variation of rice nitrogen absorption and partitioning under the haze weather condition.The research using single season rice?South japonica 46?as the experimental material was carried out in Jiangsu Academy of Agricultural Sciences from May 2013 to November 2014.In this study,we construct 4 solar radiation conditions(CK:natural light treatment;mild haze:the global radiation decreased 11^-22%,scattering radiation ratio is 51-59%;the moderate haze:the global radiation decreased 23-32%,scattering radiation ratio is 60-68%;heavy haze:the global radiation decreased 33-54%,scattering radiation is 69-87%)with PE films over the rice canopy to stimulate mild,moderate,and heavy level haze from the stage of transplanting to mature.Finally,the plant nitrogen content and absorption under different degrees haze was analyzed.The main results were as follows:1.Moderate and heavy haze decreased rice total nitogen accumulation except mild haze.The haze treatment significantly increased proportion of leaves to total nitrogen accumulation,while significantly decreased proportion of the stem sheath and panicle to total nitrogen accumulation compared to that of CK treatment.The average proportion of leaves to total nitrogen accumulation of mild haze,moderate haze,heavy haze treatmentswere 2.3%7.4%-9.3%,13.3%higher than of CK.The average proportion of the stem and sheath to total nitrogen accumulation of mild haze,moderate haze,heavy haze treatments were 0.6%?3.4-5.1%?3.5%lower than of CK,and the average proportion of the panicle to total nitrogen accumulation of mild haze,moderate haze,heavy haze treatments were 0.5%?5.3-8.5%?15.9%lower than of CK.Finally the total nirogen accumulation of mild haze was 20.03 g m^-2,which 1.8%higher than CK(19.68 g·m^-2),and of moderate and heavy haze were 17.6^-18.9 g·m^-2 and 17.3 g·m^-2,which 4^-10.4%and 11.9%lower than CK,and degree of decline was all smaller than the total radiation.Haze treatment significantly reduced the nitrogen output and the output rate of stems and leaves,but significantly increased plant nitrogen accumulation after heading stage of rice.NNACR of haze treatments were 28.3%?25.9%?25.3%?26%?29.1%,which were all higher than of CK?20.7%?.2.The haze treatment significantly increased rice nitrogen content of middle and lower leaves and had no effect on upper leaves,which the effect after booting were greater than before booting stage.The plant nitrogen content in average of treatments?light,moderate,heavy haze?than CK increased by 1.4%?3.2-6.2%?7.1%.The nitrogen content of leaves and stem sheath but the panicle under the different level of haze increased significantly when compared with that of CK,and the impact extent of rank is:leaf>stem>panicle.Leaf nitrogen content in average comparing with CK increased respectively by 3.4%?4?4-9.7%?9.2%,the nitrogen content of leaves reaching the maximum during grain filling stage.In terms of the upper leaves,the leaf nitrogen content of haze treatments and CK are basically identical;but in terms of the middle and lower leaves,the leaf nitrogen content of haze treatments is higher than CK,because more irradiation can reach the lower leaves.the SPAD and the leaf nitrogen content?LN?all had a significant positive linear correlation with the proportion of diffuse radiation to global radiation?DR/GR?,The extremely significant linear positive correlation existed between the SPAD and the leaf nitrogen rate,and the linear regression equation is:SPAD =1.05LN^-24.17,R² = 0.75,N=72.Haze seems to delay senescence of the middle and lower leaf,which make the nitrogen content uniform in the rice canopy.Thus,the growth in plant nitrogen content could be down to an increase in the middle and lower leaf nitrogen content caused by DR/GR.3.Lower harvest index caused by the increasing of leaf nitrogen content limitted"fertilizer effect" of diffuse radiationThere was a significant positive correlation between specific leaf area and leaf nitrogen content,which contribute to the enhancement of leaf area.And the leaf nitrogen content had a significant positive correlation with initial utilization efficiency of solar energy,thus helping to improve the photosynthetic rate under the low light.However,the leaf nitrogen content during grain filling stage had a significant negative correlation with dry matter and nitrogen output rate of stem leaf,resulting in the decrease of harvest index.With leaf nitrogen content increasing by 1 g·kg^-1,the harvest index decreased by 1.76%.