Influence of Planting Methods on Grain-filling Properties of Super Rice

To explore grain-filling properties of high-yielding rice under different planting methods,we studied the grain-filling processes of superior and inferior grains of two super rice cultivars(Huaidao 9 and III you 98) with Richards equation W=A/(1+Be-Kt)1/N and three planting methods,i.e.precision artificial transplanting with dry nursery middle and strong seedlings(ATR),mechanical transplanting with small seedlings(MTR) and direct seeding(DSR).The results were as follows:(1) The super rice yields under different planting methods were significantly different,ATR was the highest,followed by the MTR,and the lowest was the DSR.Compared with ATR and MTR,the 1000-grain weight and seed-setting rate of DSR were significantly lower,but the changes between ATR and MTR were different due to different types of cultivar.(2) The grain-filling processes of superior and inferior grains of super rice under different planting methods were obviously asynchronous type.The time reaching the maximum grain-filling rate(Tmax) of superior grains was early,maximum grain-filling rate(GRmax),mean grain-filling rate(GRmean),the final weight of a kernel(A) and initial grain-filling potential(R0) were significantly greater than those of inferior grains.However,the active grain-filling period(D) and effective grain-filling time(T99) of the superior grains were significantly less than those of inferior grains.(3) Compared with ATR and MTR,the GRmax and GRmean of superior grains of DSR were significantly lower,Tmax was obviously delayed,D and T99 significantly increased.The GRmax and GRmean of inferior grains of MTR were the highest,and ATR was slightly lower than DSR.For Tmax,DSR was the earliest,MTR was the second,and the latest was ATR.D and T99 reduced in order for ATR,MTR,and DSR.(4) For grain-filling characteristics of different stages,the maximum of mean grain-filling rate and contribution rate was present at the middle stage,and the contribution rates of superior and inferior grains were up to 60.53% and 50.78%,respectively.The grain-filling days,mean grain-filling rate and contribution rate of the early,middle and late stages among different planting methods were different due to grain positions.(5) 1000-grain weight was positively correlated with maximum grain-filling rate,mean grain-filling rate and active grain-filling period of superior and inferior grains,and the correlations with maximum grain-filling rate and mean grain-filling rate of inferior grains were significant.Seed-setting rate had in a degree of positive or negative correlations with the grain-filling parameters of the superior and inferior grains,however,except the active grain-filling period of superior grains,all of the correlations were not significant.The results suggested that planting methods have significant influence on grain-filling properties of super rice.Although the grain-filling processes are all asynchronous types,the grain-filling parameters such as maximum grain-filling rate and the time reaching the maximum grain-filling rate of superior and inferior grains have great difference among different planting methods.It would play an important role in improving 1000-grain weight and grain-filling rate,especially the grain-filling rate of inferior grains under the conditions maintaining the final weight of a kernel and seed-setting rate stable.