| The high yield mechanism and cultivation measures of super rice are the hot topics of research.The poor grain-filling of inferior spikelets is more aggravated in the new bred"super" rice cultivars that have numerous spikelets on a panicle.The problem about how to solve the poor grain-filling and low seed set for inferior spikelets of super rice varieties have been studied from the aspects such as leaf-cutting and spikelete-thinning,spraying exogenous hormones,different planting methods and so on.However,the mechanism underlying the poor grain filling has not been understood.Taking conventional japonica super rice Ningjing 3 and indica-japonica hybrid super rice Yongyou 12 as experimental materials,the experiment analyzes the grain-filling characteristic,photosynthesis,the accumulation of population dry matter and N,endogenesis hormones in grains,starch granule and protein bodies in endosperm by different amount of N treatments,which offers evidence for the solution to poor grain-filling of inferior spikelets and references for the improving of theories and technologies on the high production of super rice.The main results are as follows:1.NM(120 kg/hm~2)treated panicle N can effectively harmonize the problem of super rice grains and improve the maximum filling rate and the average filling rate and the grain weight in active filling stage of the inferior spikelets as a result,promote the sotting rite,the seed weighe,and then the ultimate production.However,the degrees of the contribution made by different varieties at different filling stages to grain weight are different:the middle>early>late stages for Ningjing 3,the middle>late>early stages for Yongyou 12.Appropriate administration of panicle N raised the yield of conventional super rice Ningjing 3 by increasing its grain number per panicle and,promoted the production of the large-panicle hybrid Yongyou 12 by improving their maturing rate.The decision periods on grain weight of super rices of different varieties are diverse.The grain weight of the inferior spikelets of Ningjing 3 is decided by the filling rate 10 to 20 days after flowering,while the superior spikelets of Yongyou 12 is decided by filling rate 10 to 20 days after flowering,and the inferior spikelets is decided by the filling rate 10 to 20 days after flowering.2.Panicle N fertilization could increase the SPAD-value,suppression chlorophyll attenuation rate,increase net photosynthetic rate during grain-filling stage,increase the dry matter and N accumulation after jointing,and promote the transportation of dry matter and N from vegetative organs to grains after heading of super rice flag leaf,but dry matter accumulation from heading to maturity and maturity stage,dry matter and N translocation amount,translocation rate,and contribution rate to grains of vegetative organs after heading were decreased under NH treatment(180 kg/hm~2).With the increase of the amount of panicle N fertilizer,the rate of absorbtion and utilization and the agronomic utilization of the two varieties all had firstly increased then decreased,panicle N physiological efficiency,N grain production efficiency,as well as N dry matter production efficiency were decreased and,N absorption per unit yield gradually increased.The SPAD-value,net photosynthetic rate,transpiration rate and the maximum photochemical efficiency of chlorophyll fluorescene parameter,the actual photochemical efficiency and the non-photochemical quenching coefficient of flag leaf of indica-japonica hybrid super rice Yongyou 12 were higher than that of the conventional japonica super rice Ningjing 3.The dry matter and N accumulation amount,accumulation ratio and accumulation rate from jointing to maturity period,the dry matter and N apparent translocation of vegetative organs after heading of Yongyou 12 were higher than that of Ningjing 3.The panicle N recovery efficiency,panicle N agronomic efficiency,panicle N physiological efficiency,and N absorption per unit yield of Yongyou 12 were higher than that of Ningjing 3,while N grain production efficiency,N dry matter production efficiency were lower than that of Ningjing 3.Compared with conventional japonica super rice,indica-japonica hybrid super rice has a stronger photosynthetic productivity,a higher dry matter accumulation and N absorption and utilization advantage,but it needs more N input for higher grain yields.3.NM(120 kg/hm~2)treatment can improve the seed length,width,and thickness of inferior spikelets for Ningjing 3 and the superior and inferior spikelets of Yongyou 12,and enhance the protein and starch accumulation of the superior and inferior spikelets.The administration of panicle N can increase the endogenous hormone content of grains.The endogesis IAA,ABA,Z+ZR and GA1+3 content were enhanced by the increasing of the amount of N panicle fertilizer.Panicle N treatment mainly enhanced the number of protein bodies of superior spikelets during the early period of grain filling and the density of amyloplast during the middle period of grain filling,and increased the number of amyloplast in inferior spikelets during filling period and postphored the peak time when amyloplast appeared in high amount.The endogenous IAA,ABA,Z+ZR and GA 1+3 of superior and inferior spikelets have a positive correlation or super positive correlation to grain accumulation rate while a hegative accumulation to protein accumulation rate. |
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