| Lodging has been one of the important issues in rice production. Evaluation of lodging resistance of rice plants is the focus of the lodging research, but so far, methods which have both theoretical basis and good practicality for the assessment of lodging are still less. In this study, ten rice cultivars were used to analyze all the forces including gravity, wind force, rainwater gravity and raindrop impact force upon the second basal internodes with a mechanical method, and a model for the assessment of stem lodging resistance in rice was proposed. On the basis of this, the relationships between stem lodging resistance and morphological traits, internode anatomical structure and components were investigated. The results are as follows:1. Based on the principle of material mechanics, a model for stem resistance assessment was built. Using this model, a safety coefficient (n) of a rice stem in a certain situation will be calculated, given the wind speed, rainfall and some morphological parameters. The bigger the safety coefficient is, the higher the resistance against stem lodging will be; when n<1, lodging occurs.2. By simulating varying wind speed and rainfall intensity, the external forces were thus measured; and some equations are then applied to evaluate the wind force, the raindrop impact force and the rainwater gravity, as a result, the number of parameters to be measured was lessened.3. According to the model of lodging resistance, the safety coefficients in various situations, such as in the absence of external force, in the existence of wind, in the existence of rain and windy after rain, were obtained, as well as the safety coefficient under the local common bad weather.4.The correlation analysis shows that, the safety coefficient is negatively correlated with the outer diameter, the inner diameter and the internode length of the second basal internode, but positively correlated with the stem wall thickness and the ratio of outer diameter to inner diameter.5.Both the content of starch and soluble sugar of the second basal internode have positive correlation with safety coefficient30days after heading. It indicates that non-structural carbohydrates not only met the needs of grain filling but also help to support the plant. Cellulose, hemicellulose and lignin are the important supportive components of the cell wall, for their contents in the second basal internode are positively correlated with safety coefficient. Among the common mineral elements, silicon and potassium might directly influence the ability of stem lodging resistance, considering the fact that their contents are positively correlated with safety coefficient.6. The area and the number of large and small vascular bundle are all correlated with safety coefficient, showing that vascular bundle may play an important role in lodging resistance. |
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