Physiological And Molecular Mechanism Of Plant Growth Regulators In Inferior Grain Filling Of Rice

To select the plant growth regulators having significant regulatoryeffect on the grain weight and grain filling of inferior spikelets. In this study, thelarge panicle rice variety Xinfeng2in the rice area along the Yellow River Valley waschosen as experimental material, and field experiments were conducted by sprayingexogenous compounds at heading stage at the Science and Technology Park of HenanAgricultural University from2011to2012. From the researchment of photosyntheticmaterial synthesis operation, grain storage capacity, sucrose-starch anabolic, wecould better understand the complex chemical regulation agent under inferior grainsfilling of High Yield Rice It was also further clarify the mechanism of grain filling inrice and plant hormone,which provided the technical support for improving riceproduction in Huang-Huai region. And the results were as follows:1. The chemical regulation compounds IV and V had a big impact on1000-grainweight, especially on inferior spikeles whose1000-grain weight enhanced by17.48%,16.38%when compared with CK respectively, which reached the significant level;and the two chemical regulation compounds had a promotion of seed number on a ricepanicle and seed setting rate, but the difference was not significant; the two chemicalregulation compounds had a more significant effect on the improvement of the grainappearance quality than the processing quality, and impact was more apparent on theinferior grain quality than that on superior grain. Chemical regulation compounds IVand V were determined to be the best exogenous phytohormone compounds aftercomprehensive comparison. The improvement of yield by IV and V was mainly dueto the increase of1000-grain weight and grain filling of inferior grain.2. The results suggested that SPAD value and chlorophyll fluorescenceparameters F0, Fv/Fm, ETR flag leaf under IV and V treatment were significantlyhigher than that of CK at the late stage of grain filling. And ETR was positivelycorrelated with photosynthetic rate compared with CK; SPAD value was also had a significant difference on28DAF compared with the CK. These results indicatedthat IV and V played a catalytic role of delaying leaf senescence and improving thephotosynthetic rate.3. Chemical regulation compounds IV and V could affect output andaccumulation of non-structural carbohydrate in stem and sheath of rice. Data in thestudy suggested that sugar content in stem and sheath was higher than the starchcontent; sugar and starch content in stem were higher than that in sheath; the sugarand starch in the second, third, fourth stem and sheath of top was higher than that inthe first stem and sheath at the mid-late grain filling stages. That is, the effects ofchemical regulation compounds IV and V was more apparent on sugar, starch in themiddle of the grout, and it was greater on sugar than on the starch..Effect of chemical regulation compounds IV, V on bleeding quantity of spikeneck spikelets regulation showed that the bleeding intensity performed a W-shapedchange with growth under treatment. The impact of IV, V on bleeding intensity wasthe greatest at early or late grain filling stage, and the two peak values at10,28dwere higher50.73%and58.12%,76.83%and59.30%than CK, respectively.4. Effects of chemical regulation compounds IV and V on endogenous hormone.The total contents of ZR and GA3were lower than those of IAA and ABA. Thechange of ZR, GA3, IAA, ABA was in a similar trend, generally showing a "V" fontin superior grains, and reached the peak at10d after treatment. The change of GA3and IAA content was similar in inferior grains. They both increased first and thendecreased. Above all, the effect of chemical regulation compounds on endogenoushormone was relatively obvious at early and late grain filling stage.5. Effects of chemical regulation compounds IV and V on relative expression ofenzyme genes involved in grain sucrose and starch metabolism pathways. The resultsof this dissertation indicated that IV, V improved expression of genes such as SUS,UDPGPPase, ADPGPPase, SSS, GBSS significantly, resulting in prompting theactivity of enzymes involved in sucrose and starch metabolism pathways, enhancingthe transformation of soluble sugar and sucrose to starch obviously, raising the rate ofstarch accumulation, guaranteeing the continuous grain starch accumulation at lategrain filling stage.As a whole, effects of chemical regulation compounds IV and V on grain fillingto several aspects were as follows:Firstly, the SPAD value and chlorophyll fluorescence parameters of flag leaf increased after spraying chemical regulation compounds,which would help to extendthe photosynthetic time, thus promoting grain filling at the late stage; secondly,chemical regulation compounds increased the assimilative matter in stem or sheathand bleeding quantity of spike neck spikelets, which promoted sugar in stem andsheath transporting to grain; thirdly, the accumulation and its rate in grain wereimproved because of the increasing of endogenous hormones content and key enzymegene expression involved in the process of grain starch synthesis which enhanced theactivity of the grain storage and the conversion efficiency of grain sucrose to starchafter chemical regulation compounds treatment.