Study On Effects Of Root Physiological Characters On Grain Development Of High-yielding Summer Corn

In this research, three summer corn varieties with different yield potential asexperimental materials, zhengdan958, nongda108and denghai661, and plant populationchosen as control measures (60000plants·hm^-2,75000plants·hm^-2and90000plants·hm^-2) inthe field experiments, the objective was to clarify effects of root physiological characters ongrain development of high-yielding summer corn and its mechanism so as to provid theorialand techanical support for high and stable yield. And the main results were as follows:（1） The high population-tolerant property variety followed by high yield potential. Theyield of ZD958and DH661performed increase as plant population intensified, but the one ofND108had an opposite tendency. The highest grain yield of three varieties were obtainedunder the population of75000⁹0000,90000and60000plants·hm^-2, respectively. With thepopulation increase, the ear number and1000-kernel weight decreased. Compared to thecorrelation index between yield and its component under high population, the data showed1000-kernel weight> effective ear number per area>grain number per ear. Consequently, thehigh-yielding of summer corn mainly rely on the improvement of ear number and grainweight.（2） The grain weight enhancement depends on not only more endosperm cells, but alsohigh starch accumulation. Compared to the number of endosperm cells under the same plantpopulation, the data showed DH661>ZD958>ND108.Along with plant population intensified,the number of endosperm cells and the mean rate of cells proliferration decreased for all threevarieties. Plant population affected grain filling parameter, including initial potential of graingrowth, grain filling rate and active filling period, lastly, influented the grain weight. Thecorrelation analysis between grain weight and grain filling parameters indicated the grainfilling rate was the main influence factor by plant population.（3） With the increase of plant population, the content of ZR, ABA, GA and IAA in grainaffected endosperm cell proliferation and grain filling. The correlation analysis suggested thatZR in grain positively correlated with initial potential of endosperm cells proliferation,maximal grain filling rate and mean grain filling rate significantly, but had a negativecorrelation with active proliferation period remarkably; ABA and GA at early grain fillingstage positively correlated with maximal and mean proliferation rate; IAA at early and middlegrain filling stage had a positive correlation with maximal and mean grain filling rateremarkablely.The content of ZR, ABA, GA and IAA positively correlated with maximal andmean grain filling rate. （4）The main amino acids were Thr, Glu, Lys, His and Ala, the secondly were Val, Ile,Leu, Asp, Tyr and Phe, and the other amino acid content were akwfully few. The Mg, B andZn content were high in bleeding sap of summer corn, and the Fe content was low. Thebleeding intensity and flux of hormone and mineral elements performed decreased along withplant popualtion increased.The decrease percentage of all varieties showedDH661<ZD958<ND108. The data indicated high-yielding variety had a little decrease of rootfunction under high population.（5）The hormone content and balance could be affected by hormone content in rootbleeding sap remarkably.The correlation analysis showed, at early grain filling stage, ZR andABA in roots and ABA and GA in grains had a positive correlation significantly; ABA in rootspositively correlated with ABA, GA and IAA in grains,however, GA in roots had a positivecorrelation with ZR, ABA, GA and IAA in grains, at middle stage of grain development.Inlate grain filling stage, ABA in roots and ABA in grains had a positive correlation remarkably,while, IAA positively correlated with ABA and GA in grains significantly.