| A field experiment was conducted with three wheat cultivars(Yumai 49-198,Lankaoaizao 8,and Yanzhan 4110)with different tillering capacity.The characteristics of tissue structures and formation of spike from the tillers in main stem and tillering of wheat with different tillering capacity were studied to illuminate the mechanism of spikes.In this study,the morphological specificity,accumulation of dry matter and metabolism of nitrogen were also studied to explain the difference of the development and the distribution of the nutrients among main stem and tillering.Through 15 N tests,the nitrogen absorption,nitrogen translocation,nitrogen distribution and nitrogen fertilizer utilization rate of main stem and tillering were analysed to illuminate the difference of among nitrogen fertilize utilization and distribution.The following is the main results in this study.The difference of antioxidant enzymes metabolism of main stem and tillering were discussed to elucidate the physiological basis of antioxidant.1.The differences of earing rate rules,form structure and dry matter accumulation and yield in different tillering capacity wheat.The result showed that,the tillering numbers and earing rates decreased with the density increase.The highest tillering number of three cultivars YM49-198,LKAZ8 and YZ4110 at middle density and high density decreased by 54.85%、51.02%、59.09% and 79.68%、73.47%、63.64% respectively contrast to low density.The stem height increased with the density increase,and the small tillering height was lower than other tillering.With the density increase,the leaf age decreased.It increased slowly after jointing stage and had great difference with stem,which was the symbol of tillering polarization.The result showed that,the low earing rate cultivar LKAZ8 had stronger dry matter accumulation ability in stem and single tillering.Both of the dry matter accumulation of single organs and total amount decreased with the density increase.For high earing rate cultivar,higher dry matter accumulation appeared at higher density,while it appeared at middle density for lower earing cultivar LKAZ8.In this study,the grain yield was highest at middle density for YM49-198 and YZ4110,while it was highest at high density for LKAZ8.Ear length,spikelet numbers per spike,grain number,grain weight and middle spikelet granulation numbers decreased with the increase of tillering position,while Ineffective spikelet numbers per spike showed the opposite trend.Spikelet numbers per spike,grain number,grain weight and middle spikelet granulation numbers decreased with the density increase,while Ineffective spikelet numbers per spike showed the opposite trend.Nitrogen application increased tillering numbers at early stage,and had little influence on spike numbers.LKAZ8 had lower earing rate,just occupied by 33.10% and 42.75%(low nitrogen),36.50% and 31.36%(middle nitrogen)、52.83% and 53.93%(high nitrogen)with YM49-198 and YZ4110.Nitrogen application increased plant height,stem diameter and leaf age of middle and small tillering.The effect of nitrogen application on yield were different with different cultivars.For LAKZ8,the yield was highest at high nitrogen than low nitrogen and middle nitrogen,while YZ4110 got highest yield at middle nitrogen and high nitrogen.The best predictive model for dry matter accumulation was the Richard curve equation,i.e.,y=1.1435/(1+e0.2776-4.6558x)1/0.1130,r=0.9927.Overall,dry matter accumulation could be divided into early,middle,and late phases based on the two inflexion points in the rate equation.The dry matter accumulation rate was very sensitive to density in the middle phase.The relative accumulated temperature was 0.53 at the maximum dry matter accumulation rate,when the dry matter weight was about one-half of the total weight.It indicated the importance of improving wheat yields by enhancing field management in the early growth phases,including the cultivation of sound seedlings and the construction of appropriate populations.The average rates of dry matter accumulation were the most important factor influencing dry matter accumulation according to path analysis.Higher average rates of dry matter accumulation had significant effects on stabilizing and increasing the dry matter weight of wheat.2.The differences of tillering node area and tissue structure in different tillering capacity wheatThe result showed that,the tillering node area decreased with the increase of tillering position.The tillering node area of wheat with lower tillering ability were regulated by density strongly,the tillering node area decreased with the increase of wheat density.Among three cultivars,the tillering node area showed YM49-198> LKAZ8 > YZ4110.The thickness of stem wall and mechanical tissue of stem and tillering decreased with the increase of density and tillering position in three different tillering capacity wheats at jointing stage.The thickness of stem wall and mechanical tissue of LKAZ8 were higher than other cultivars.The thickness of stem wall and mechanical tissue in primary tillering were higher than secondary tillering,and they were also very low in senescence tillering than stem and other tillering.The inner,middle,outer and total vascular bundle number decreased with the increase of density and tillering position.The vascular bundle area,phloem area and the number of xylem conduit also showed the same trends.The vascular bundle developed slowly and the small vascular bundle were not formed,which was the important reason for its senescence.The differences of vascular bundle development between stem and tillering was small in high earing rate wheat,while it was very large in lower earing rate wheat LKAZ8 which has high stem advantage.The tillering node area at winter stage were positively related to grain numbers,grain weight and effective spikelet numbers,especially in LKAZ8.The inner ascular bundle area,inner total ascular bundle area and inner total phloem area were related to three spike characters closely.The inner ascular bundle area and inner total ascular bundle area were the important index for grain numbers and grain weights,while inner total ascular bundle area was the important index for effective spikelet numbers of wheat.3.The nitrogen metabolism characteristics of stem and tillering in different tillering capacity wheatIn this study,the wheat leaves had three kinds of isozymes(GS1、GSx and GS2),the GS2 activities were higher than GS1 and GSx.The decrease of nitrogen metabolism key enzymes GS,GOGAT,GS2 and GSx activities affected the nitrogen assimilation abilities,while the increase of GS1 activities improved nitrogen transport abilities in wheat small tillering since jointing stage.The lack of nitrogen nutrient induced by decrease of nitrogen content and accumulation amount was the important reason for the small tillering senescence.The key enzymes activities,nitrogen content and accumulation amount in stem were higher than other tillering in LKAZ8.It indicated that LKAZ8 has stronger stem advantage,and the unbalanced nutrient distribution was one of the reasons for is lower earing rate.Before jointing stage,the small tillering has higher amino acid content.It indicated the breakdown of nitrogen in small tillering,which also was a approach of nitrogen transport and redistribution.The soluble protein in small tillering decreased rapidly after jointing stage,which accelerated its senescence.Nitrogen transport amount decreased with the increase of tillering position in three cultivars,and showed LKAZ8>YM49-198>YZ4110,which related to higher grain weight in LKAZ8.The key enzymes activities were positively significantly related to nitrogen content and nitrogen accumulation amount,which can regard as judgement for nitrogen nutrient level.Nitrogen application increased nitrogen content of leaves at jointing and anthesis stage.Nitrogen use efficiency was higher at N8 for high earing rate cultivar,while it was higher at middle nitrogen for LKAZ8.Both the nitrogen translocation nitrogen absorption from soil was higher than that from fertilizer.There were great differences of nitrogen absorption and distribution among different organs,which showed grain>Stem,sheath and glume>leaf.4.The differences of MDA content and antioxidant enzyme activities of stem and tillering in different tillering capacity wheatThe result showed that,the MDA content in small tillering of three wheat cultivars decreased firstly and then increased,and it was higher than stem and other tillering at jointing stage.So,the small tillering began to die and lots of MDA accumulated at jointing stage.After jointing stage,the SOD activities of small tillering achieved peak value in YM49-198 and LKAZ8,while it decreased straightly in YZ4110.The CAT activities in small tillering of three wheat cultivars increased firstly and then decreased,and it was higher than stem and other tillering at jointing stage.Nitrogen application was important for delay senescence.The result showed that,nitrogen application increased SOD and CAT activities,decreased MDA content,which was good at delay senescence,and the MDA content was lowest at middle nitrogen. |
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