Mechanism Of Lodgin Resisrance And Relationship Between Cultivation Factors And Lodging Of Rapeseed (Brassica Napus L.)

Centering on the lodging resistance of rapeseed (Brassica Napus L.), four experiments on varienties comparison, density, nitrogen application stage and hydrops were conducted in 2006～2008 to study the agronomic traits, physiological and chemical charaters and microstructure of rapeseed varienties with different lodging resistance, strong, mediun and weak, and effects of some cultivation factors on lodging and quality of rapeseed. The main results as follows:1. Lodging of rapeseed mainly occurred at post-maturation stage, about 15 days before harvesting. The correlation coefficients between agronomic trats and lodging index showed the trend of plant height> main inflorescence length> branch height > number of primary branches> silique number> silique density> width of root colla > branch length. Varieties with strong lodging resistance showed many features, such as moderate plant height, lower branch height, short main inflorescence, medium number and length of primary branches, more siliques per plant, big silique density, quickly increasing of root colla width, and so on.2. BP neural network model was used to forecast the lodging index and five agronomic characters which clearly related to the lodging resistance, results showed that the fitting was good and the forecasting values of two samples entirely lied in confidence interval. A regression equation was gained by stepped regression, Y=-2.033-0.052X1+0.013X2+0.092X4+6.423X7-4.950X8-0.385X9, in which Y, X1, X2, X4, X7, X8 and X9 represented lodging index, plant height, biomass and branch height, (bolting stem+main inflorescence)/(shortening stem+ elongated stem), bolting stem/ elongated stem, (bolting stem+elongated stem)/shortening stem respectively. The results showed that the effect of proportion of different stems of rapeseed on lodging was bigger than that of plant height and biomass on lodging.3. In tested materials, lodging resistance of Zhongshuang No.9 was strongest, while that of XYY 6 was weakest, and there existed significant difference in three ratios, (bolting stem+main inflorescence)/elongated stem, (bolting stem+main inflorescence)/ (shortening stem+ elongated stem) and bolting stem/elongated stem, between the two varieties. As for Zhongshuang No.9, the three ratios were 2.10,1.61 and 0.92 respectively, and their were 2.87,2.27 and 1.57 for XYY6. The three ratios between two strong lodging resistance varieties, Zhongshuang No.9 and Fuyou No.3, were very close. At late flowering stage, root/shoot ratio of Zhongshuang No.9 was highest, 22.4%, it was significantly higher than that of weak lodging resistance varieties.4. Significant negative correlation existed between K content and protein content, and resistivity of main stem. Significant positive correlation existed between water content of main stem and protein content, yield per plant, while significant negative correlation existed between water content of main stem and lodging resistance. At late flowering stage, correlation coefficients between biochemical composition and lodging index showed the trend of crude fiber> Ca> total sugar> K> protein, and which showed the trend of C> ratio of dry weight to fresh weight in cortex of root colla> fiber> C/N> lignin> N. At maturity, contents of lignin, N, fiber, Si and K in main stem of strong lodging resistance varieties were 1.189.1.462,0.904.7.158 and 0.182 times to those in main stem of weak lodging resistance varieties, respectively. Significant positive correlation existed between water content in cortex of root colla and lodging index.5. There existed clear difference in lignin characters between rapeseed varieties witg different lodging resistance. As for strong lodging resistance varieties, lignin was thick, arrangement of cell was regular and linear, and the arrangement direction was basically identical to main stem. As for weak lodging resistance varieties, lignin was thin, arrangement of cell was irregular. There existed clear difference in ray distribution between two types of varieties, ray of strong lodging resistance varieties connected tightly with phloem, which has not fault at cambium, while ray of weak lodging resistance varieties connected loosely with phloem.6. Expeiment of density showed that plant height of rapeseed was increased by density. Content of lignin in main stem was increased by density, while it was not significant. Genotype difference existed in correlation of quality of rapeseed and density. Significant positive correlation existed between yield per plant and root volume and width of root colla. Correlation between root number, root width and yield per plant was clear, while it was not significant, and the correlation between others root character and yield per plant was not clear. The correlation between lodging index and the length of the longest root, number of roots, width of root and root colla, root volume showed negative, while not significant.7. Hydrops in field at late growth stage of rapeseed resulted in clear decrease of yield and oil content, greater lodging and slightly increase of protein content, while content of oleic acid and glucosinolate changed unclearly. Under the same level of nitrogen fertilizer, backward removal of nitrogen fertilizer had not significant effect on yield and content of linoleic acid and protein, while it resulted in significant decrease of content of oil and oleic acid. If the proportion of nitrogen fertilizer at late growth stage reached to 70%, the lodging of rapeseed increased significantly.