Effect Of Nitrogen On The Assimilate Accumulation And Translocation In Wheats

The accumulation and translocation of the water soluble carbohydrate are crucial for theyield of wheat. The time of duration of grain filling is the crucial key for yield formation,while more water lossed due to evaporation in the Loess Plateau, so that wheat is easily tosuffer from drought during grain filling, it seriously influence the de novo photosynthesisduring grain filling. So the translocation of the water soluble carbohydrate storaged in thestems to grain is more important for the yield of wheat. An experiment was implemented toinvestigate how the nitrogen (N) fertilization affects the mobilization of assimilation duringthe grain-filling period, the treatments involved in5different nitrogen levels, N10kg/ha; N280kg/ha;N3150kg/ha; N4195kg/ha; N5300kg/ha. The main results showed as following:1. The earliest net remobilization of carbohydrates happened in glumes, for differentsource organs, the lower stem contribution most dry matter to grain, the increase of the Napplication allowed a lower use of the pre-anthesis carbon reserves in favor of greater denovo photosynthesis during the grain-filling period. The more dry matter was accumulatedfrom de novo photosynthesis, which is a guarantee for the higher yield under semiaridconditions.2. Nitrogen fertilization significantly increase nitrogen accumulation from seedling stageto jointing stage in wheat. the nitrogen content in various organs ranked from high to low asfollows: grain, leaf, stems, sheath and chaff in wheat at harvest stage. The nitrogen utilizingcoefficient of plant was higher in N3,4, however lowest nitrogen utilizing coefficient wasfound in N5. Nitrogen fertilization application significantly reduces partial factor productivityfrom applied nitrogen and Physiological efficiency of applied nitrogen. Grain nitrogen comesmainly from the leaves and stems, nitrogen fertilization significantly increase the total ratios andamounts of transported storage nitrogen, and the contribution ratio of transported nitrogencould be increased before anthesis, and grain yield and protein yield were also increasedsignificantly. More nitrogen fertilization application, higher GS and GDH activity in leaves,glumes, sheaths and stems, it was very important to grain nitrogen accumulation.3. Highest yield,WUE, spike number and grain number per spike were found in N4.Nitrogen fertilization significantly increase spike number and grain number per spike. Yetspike number is the main contribution of yield, the lower yield was mainly due to smaller spikenumber in N1,2.1000-grain weight is highest in N1, so we have conducted that reduced tillering and grain number per spike to maximizeproduction of viable grain in the N1conditions.