Plant Type Characteristics In Wheat And Its Nitrogen Regulation Approach

The objective was to establish the regulation approaches of ideal plant type for high yielding. The split plot design was conducted with main plot of nitrogen fertilizer, and sub-plot of wheat cultivars differing in plant types (compact-high stalk type, Ningmai 9; compact-low stalk type, Aikang 58; Middle type, Yangmai 12; loosely type, Huaimai 17). This study focused on the effect of plant type and nitrogen fertilizer application rate on morpho-physiological characters of leaf and stem, canopy structure and light distribution, accumulation and translocation of carbon and nitrogen, grain yield, and the relationships among those characters.The change patterns of leaf morphology with growth progress were characterized based on leaf morphological properties of main stems under different nitrogen rates with four wheat cultivars. The result showed that the trend of leaf length and width, and leaf angle looked like "S" shape with GDD. In contrast, Leaf SPAD increased gradually with GDD and reached the maximum at anthesis, and then decreased slowly. Leaf length and width, and leaf angle exhibited quadratic polynomial with different leaf position. Nevertheless, single leaf area had an "up-down-up-down" trend with leaf position. Leaf characteristics had a remarkable difference between cultivars at major growth stage. Nitrogen rate affected greatly leaf length and width, leaf angle, SPAD, and leaf area just at anthesis and grain filling period. Leaf length and width, leaf angle of different leaf position as affected by plant type and nitrogen rate had not the same response, but SPAD and distance between neighboring leaves of different leaf position had the same response. Difference of top two leaves leaf angle in Yangmai 12 and Huaimai 17 was larger than in Ningmai 12 and Aikang 58. The distance between neighboring leaves associated not only with plant type, but with also plant height. The distance between flag leaf and top 2nd leaf was the main difference of wheat cultivars with different plant type, as well as distance between top 2nd leaf and top 3rd leaf. Nitrogen rate strongly affected leaf length, leaf angle and SPAD, but had no effect on leaf width, leaf area, and distance between neighboring leaves at major growth stage. Nitrogen rate significantly affected leaf length of top three leaves and leaf width of top two leaves, but did not affect leaf width of top 3rn leaf. Nitrogen rate affected length and width of flag leaf more than that of top 2nd and 3rd leaf. Nitrogen rate increased leaf SPAD and leaf angle of top three leaves.The pattern of stem characteristics and the effect of plant type and nitrogen rate on plant height, and length and width of internode was analyzed based on time-course observation on plant height and internode length and width of main stems. Plant height changed like "S" shape, and fitted well to Logistic equation during growing stage. Top four internode length was in the order: internode below ear> top 2nd internode> top 3rd internode> top 4th internode. The 4th internode width of Ningmai 9 and Aikang 58 and the top 2nd internode of Huaimai 17, and Yangmai 12 were the maximum. Nevertheless width of internode below ear was the minimum. Parameters derived from equation of plant height had great difference between nitrogen rates and plant types. Internode length and width correlated positively with nitrogen rate. Nitrogen rate strongly affected plant height at stem elongation period, full heading period and maturity, not yet at returning green. Nitrogen rate and plant type significantly affected internode length and width, but did not affect plant height index. Nitrogen rate and plant type influenced spike length, and nitrogen rate were positively related with spike length. So, there is a significant difference in plant height and internode of different plant type and nitrogen rate. Nitrogen rate greatly increase plant height, internode length and width, spike length.Wheat canopy structure characteristics pattern was analyzed based on time-course observations on canopy characteristics under different nitrogen rates with four cultivars. The result showed that leaf area index and tiller number, which reached the maximum at booting stage and jointing stage, presented a single-peak curve, respectively. Net photosynthetic rate of leaf decreased gradually from flowering. Population light transmittance changed like parabola curves in diurnal course, and reached the maximum at noon. There was a great difference of plant type in LAI, SPAD, canopy green leaf area and specific leaf weight, not yet in population tiller number. The vertical distribution of green leaf area in four cultivars had significant difference. Nitrogen rate significantly affected LAI, SPAD and specific area weight. Nitrogen fertilization had a remarkable difference on population tiller number at booting and harvest. Ningmai 9 and Aikang 58 had a increase trend in SPADmax、GDDmax、Rinf2 and GDDinf2 with nitrogen rate increasing, but Yangmai 12 and Huaimai 17 had a reverse trend. Nitrogen rate enhanced tiller number, specific leaf weight, net photo synthetic rate and maximum leaf area density, and made level of maximum leaf area density gone up.Carbon and nitrogen accumulation and translocation pattern and difference of grain yield in four cultivars were analyzed based on time-course observation on dry matter, nitrogen content, grain yield and its components. The result showed that relative dry matter and proportion of organs to biomass with relative thermal time from sowing fitted better to an Richards model and vapor pressure model, respectively. The dry matter accumulation duration of early stage decreased with nitrogen rate increasing under different wheat cultivars, whereas that of the third stage increased, and that of the second stage obviously differed from cultivars. Although the average growth rate Ra and maximum growth rate Rmax of dry matter increased with nitrogen rate increasing, that of dry matter dry mater decreased when nitrogen rate exceeded 150 kg ha-1, Transfer amount of soluble sugar ranked in the order of stem and sheath, leaf blades, and spike. Translocation rate of soluble sugar ranked in the order of stem and sheath, spike and leaf blades. Nitrogen fertilization affected remarkably transfer amount of soluble sugar in leaf, stem and sheath and spike of wheat cultivars. Nitrogen translocation amount of stem and sheath, spike and leaf in four wheat cultivars had significant differences. Nitrogen increased pre-anthesis nitrogen accumulation and nitrogen accumulation at maturity, but response of post-anthesis nitrogen assimilates in four wheat cultivars to nitrogen fertilization were different.Dry matter and nitrogen accumulation and translocation, grain yield, correlation between grain yield and its components and plant type characteristics, canopy characters, carbon and nitrogen accumulation and translocation were analyzed based on time-course sampling observations. The result showed that grain yield and 1000-grain weight correlated significantly with the characteristics of flag leaf, but did not with that of the second and third leaf. Grain number per spike positively associated with characteristics of top three leaves. Moreover, grain yield,1000-grain weight, grain number per spike positively associated with length of upmost internode and second internode from top.1000-grain weight also significantly associated with length of second internode, and grain number per spike remarkably correlated with third internode. Grain yield and spike number closely associated with stem and tillers number, but 1000-grain and grain number per spike did not correlated with stem and tillers number. Grain yield,1000-grain, grain number per spike, and spike number significantly associated with post-anthesis dry matter accumulation, translocation amount of pre-anthesis stored assimilate, contribution of post-anthesis stored assimilate to grain yield, but had no relationship with contribution of pre-anthesis stored assimilate to grain yield. Grain yield,1000-grainweight and grain number per spike positively associated with translocation rate of pre-anthesis stored assimilate (TAR). Spike number with TAR showed a negative correlation. Grain yield,1000-grain and spike number with nitrogen translocation amount, nitrogen transportation efficiency, contribution of post-anthesis nitrogen assimilation to grain had a positive correlation, and with contribution of translocation amount of nitrogen accumulation to grain had a negative correlation.