The Research On Lodging Extra-intro Inducing Factors And Stem Dynamics Character In Spring Wheat

28 lines and 1 cultivar of spring wheat were planted under 4 densities in the design of split plot to study systemically on the lodging of the wheat genotypes in different growing periods and rainfalls. The extent of lodging of wheat cultivar and lines was investigated after heading when raining and 7 times at all. The lodging of spring wheat was observed to happen mainly in 2 periods or the period of quick increase of ear weight and the period from late milk stage to early dough stage with rainfall. The correlation between lodging and rainfall was not found in the range of the amount of precipitation and the rainfall might be one of the factors to lodging. The extent of lodging resistance of a line was observed to be different under 4 densities and in different periods and the cultivar (lines) in the trial could be divided into 5 groups or heavy lodging, no lodging, lodging induced by density, increase of lodging with growth and lodging induced by many factors. So the strategy of wheat breeding and wheat cultivation should meet to the different groups.A load experiment was designed with line 02-4258 and 01-4488 both of none lodging and even height in the internode under ear. The results showed that a large difference between the elasticity and plasticity of a stem was found in different loads and lodging of wheat in the field might be caused by little force during long time. The correlation between the limit of elasticity and the limit of strength of a stem of line 02-4257 was observed when measured the limit of elasticity and plasticity of a stem, the curve of stress-strain after loading, the extent of recovering after unloading. The measurement of lodging extent was in more precision by the limit of elasticity than by the limit of strength. The curve of stress-strain performed in irregular S shape which could be divided into 3 stages or elastic stage, plastic stage and creep stage. Combining with the analysis of recovering extent, the ranks of lodging should be determined that 0 degree would appear in the elastic stage and 1-2 degree in the beginning of the plastic stage and 3-4 degree in the creep stage.The strength of internodes was investigated in 3 periods with none lodging line 02-4068, heavy lodging line 02-4541, density inducing lodging line 01-4488 under 4 densities. The results showed that the up section of a internode was weaker than the down-section of the same internode in internode 1 and internode 2 under ear, but the down-section of internode 1 under ear was stronger than the up-section of internode 2 and the distribution of strengths in the internode 1 and internode 2 under ear was common in 29 wheat genotypes under 4 densities. And the phenomena ofthe down section of internode 2 under ear was stronger than the up section of internode 3 is not performs regularly. This might be due to active meristem in down section of internode 1 under ear after heading and non-active meristem in other internode inferred by the observation of apogeoesthetic growth after lodging of wheat. A large change was found in the strength of internode 5 under ear by the measurement of internode strength and this internode, therefore, should not be used to evaluate the strength of stem in wheat. The strength of internode 4 and internode 5 under ear performed stably and was able to represent the strength of stem of a genotype. The strength of down section of internode 1 under ear appeared a increase with growth under 4 densities and no increase in other internodes. A large dropping in the strength of bottom internodes of a stem occurred in the latter period of growth in some lines which heavy lodging in these lines happened several times. The strength of internode 2 and internode 3 was spotted between that of internode 1 and of internode 4 under ear, and a little increase of strength with growth in the internode 2 and internode 3 happened. The ratio of strength of up internode to that of bottom internode in a stem was found to increase largely in lodging lines comparing with none lodging lines. And further analysis indicated that the ratio of strength was lower in none lodging lines and larger in heavy lodging lines. The ratio of strength would influence the position of pressure curve in a stem after stressing in the field. The investigation of the pressure curve in the field showed that the pressure curve had a close relation to the direction of lodging and could give a evaluation of the lodging resistance of wheat genotypes to some extent. The 50%-60% of the length of internode 1 under ear to plant height in the ideal plant type was inferred by means of the relation of the ratio of strength and pressure curve. The increase of the ratio of strength in latter growth period corresponded with the lodging in the same period.The change of plant height and ear weight of 10 lines with growth were analyzed from flowering to ripen with every sixth day samples. The results indicated that the plant height was unchanged after flowering and the ear weight would increase very quickly after flowering and then reach to stability. The stage of ear weight near to maximum would be the period of easy lodging.The strength of bottom internodes would decrease with the increase of density according to the distribution of the strength of bottom internodes in 4 densities. The strong stem types were very few in 4 densities and fewer in the high density.Lodging was due to the force induced a slight change of stem structure after force loading, and the slight change of stem structure would be accumulated to result to a unharmonious stem structure and to have the stem caught by force easily and to induce the wheat lodging by means of the analysis of the lodging happening process. The process of lodging in the field could be divided into 3 stages: the preparative period of lodging, the first lodging period and the second lodging period. The performances in every lodging period were in diversity.At last the strategy of wheat breeding and ideal plant type towards none lodging were discussed.