Effect Of Nitrogen Rate And Planting Density On Grain Number Formation And Its Physiologic Metabolism In Wheat

Grain number was one of yield components, and nowaday improving grain number was one of major ways to achieve higher yield. Nitrogen and plant density were two important cultivation techniques affecting grain formation. So understanding the effects of nitrogen rate and plant density on grain number and its physiologic metabolism in wheat were very important.The field experiment was conducted with two varieties (Nannong0686, Yannongl9), two fertilizer nitrogen rates (210,270kg/hm2), two density levels (1.5illion and 2.25million plant per ha) and two top-dressing levels (5:3:2,5:2:3) to study the Effects of nitrogen and density on yield and group structure and carbon-nitrogen metabolism and stem tissue vascular structure, and analyzed the physiologic basic and anatomy basic. The main results were as follow:1. Grain yield increased with increase of nitrogen rate, plant density and jointing fertilizer. Low density increased grain number, visible floret number, fertile floret number and floret setting rate of both main stem and tiller significantly. Grain number, fertile floret number and floret setting rate of both main stem and tiller increased with increased nitrogen application rate in low density, and decreased in high density. Topdressing ratio mainly affected grain number of tiller, which got higher fertile floret number and floret setting rate with increasing booting fertilizer. In all the treatment factors implied, we found that variety and density were the main effects on grain number formation, followed the nitrogen, topdressing was the minimum, which mainly impacted the visible and fertile floret number of both main stem and tiller, especially the tiller. Optimal treatment of getting higher grain number of nannong0686 and yannongl9 were D150N270N1 and D150N270N2 respectively.2. Lower plant density and higher nitrogen rate increased leaf area, chlorophll content of functional leaf, leaf photosynthesis and conten of soluble sugar and sucrose, thus improved floret development, increased number of visible and fertile floret and floret setting rate, thereby increased grain number. The physiological mechanism of higher grain number of both main stem and tiller of two varieties was that the source organs had stronger leaf photosynthesis, source and sink organs had an coordinated C/N at critic's stage of floret degradation, which decreased floret degradation and increased number of fertile floret. The physiologic reasons of tiller got less grain number than main stem were that tiller got a less carbohydrate, higher nitrogen content and uncoordinated C/N.3. The vascular bundles number and area of internodes under spike significantly increased with the decrease density. The Effect of nitrogen was lower than density. The phloem and xylem area was significantly higher under N270 treatment than N210 at low density. The effect of topdressing on vascular tissue structure depending on the varieties. Nannong0686 had a better vascular tissue structure under N1 treatment while Yannongl9 was under N2 treatment. The experiment analyzed the correlation between fascicular system and spike traits. The result showed that there were significant positive correlation between fascicular system and number of grain, visible floret, fertile floret,floret setting. Besides, big vascular phlem area of tiller number and grain, fertile floret number had significant positive correlation. Fascicular system of main stem was better than tiller.To sum up, lower density and higher nitrogen rate with increasing jointing or booting nitrogen fertile application would decrease the proportion of floret degradation, increasing fertile floret number, thereby increasing grain number. The physiological mechanism of higher grain number of both main stem and tiller of two varieties was that the source organ had a stronger leaf photosynthesis, suitable soluble sugar content, source and sink organ had coordinated C/N at floret degration stage, which decreased floret degradation and increased number of fertile floret. More vascular number and bigger area were the anatomy basic of big spike. Optimal treatment of getting higher grain number of nannong0686 and yannong19 were D150N270N1 and D150N270N2 respectively.