| Rice is the most important grain crop in the world, which has a high position in grain production and keeps the balance of the world food. With the development of rice breeding, most breeders agree that the effective way to raise yield is to increase plant height which can increase the biomass. But during the rice production, lodging happens more and more frequently, which badly decreases yield and quality of rice and causes enormous economic losses. At present, lodging resistance in semi-high-stem has not been researched much. This paper researched the relationship between stem-sheath morphological and physiological traits and lodging resistance in semi-high-stem hybrid rice with higher biomass. And on this basis, further experiments of plant growth regulator and nitrogen fertilizer management had been used to research the relationship between stem-sheath physiological traits and lodging resistance in semi-high-stem hybrid rice with higher biomass. The results were as follows:1. The relationship between stem-sheath morphological and physiological traits and lodging resistance in semi-high-stem hybrid rice with higher biomassThe experiment researched the relationship between stem-sheath morphological and physiological traits and lodging resistance with six semi-high-stem hybrid rice with higher biomass combinations (Zhunliangyou 527, Guangliangyou 1128, Xiangliangyou No.2, Y2, Y900, Shenliangyou 1813). The results showed:the relationship between plant height and lodging resistance was not significant, which means the combination with high plant height was not always weak in lodging resistance. The combinations with strong lodging resistance had short basal internode and thick basal stem morphological characteristics. Correlation analysis showed that the first, second and third basal internode were highly significantly and positively correlated with lodging index (r=0.70**、r=0.70**、r=0.71**), but the major axis diameter, minor axis diameter and wall thickness of basal stem had significant or non-significant negative correlation with lodging index (r=-0.42、r=-0.23、r=-0.52*). The results found that the first, second and third basal internode of lodging susceptible combinations were significant longer than those strong lodging combinations, but its major axis diameter, minor axis diameter and wall thickness of basal stem were less than those strong lodging combinations. The number and area of vascular bundle were negative correlation with lodging index, but not significant. It had less effect on improving lodging resistance relative to other morphological characteristics.Physiologically, the content of soluble sugar, cellulose, lignin, K, Si and C/N in stem-sheath are the key indicators of the research of elasticity lodging resistance. The results were as follows:1) the stem-sheath had high C/N which meant it had enough carbohydrate content and the stem’s elasticity was good. It had strong lodging resistance. The high C/N in stem-sheath was good for raising ability of lodging resistance and increasing yield.2) The stem soluble sugar content was gradually decreasing with the growth process moving forward. The amount of soluble sugar in stem-sheath was not significant correlation with lodging index, however, it can increase the amount of cellulose and lignin, which was good for the synthesis of structural carbohydrate and strengthened the stem elasticity.3) The amount of cellulose in stem-sheath was highly significant and negative correlation with lodging index (r=-0.65**, r=-0.61**), while the amount of lignin in stem-sheath was significantly and negatively correlated with lodging index (r=-0.57*, r=-0.52*). Keeping high amount of cellulose and lignin in stem-sheath can strengthen the ability of lodging resistance at late growth stage. Meanwhile, the higher the content of lignin was, the less effective ears were.4) After analysis the relationship between dry matter weight and lodging index in semi-high-stem hybrid rice with higher biomass, it showed that the strong lodging resistance combinations had higher dry matter weight but lower matter export rate. On the contrary, the lodging susceptible combinations had lower dry matter weight but lower matter export rate. Correlation analysis indicated that stem dry matter weight was negative correlation with lodging index and sheath dry matter was significantly and negatively correlated with lodging index (r=-0.48*). The high matter export rate of stem-sheath was significant to yield, but if the stem-sheath had lower dry matter and high matter export rate, the stem substantial degree would significantly decrease and the elasticity of stem would decrease, too.5) The amount of K and Si in lodging susceptible combinations were significant less than those strong lodging resistance combinations. The analysis indicated that the amount of K in stem was significant and negative correlation with lodging index (r=-0.50*) and the amount of K and Si were significant and positive correlation with the amount of cellulose, lignin and dry matter weight in stem-sheath. It indicated that the amount of K and Si can increase the amount of cellulose, lignin and dry matter weight in stem-sheath, which meant the amount of K and Si were able to improve the ability of lodging resistance indirectly.2. The effect of plant growth regulator on physiological traits of lodging resistance in semi-high-stem hybrid rice with higher biomassLifenglin (prohexadione calcium) was able to improve the ability of lodging resistance of the semi-high-stem hybrid rice with higher biomass, but GA3 was able to weaken the ability of lodging resistance. With treatment of Lifenglin, the content of total K, total Si, cellulose, lignin and stem C/N had increased, but no significant difference. Instead, with the treatment of GA3, the content of total K, total Si, cellulose, lignin and stem C/N had a slight decline, but no significant difference, either. In a word, plant growth regulator (Lifengling, GA3) only had some effect on physiological traits, its major role was playing a leading role in changing the morphological traits, such as lengthening or shortening the basal internode.3. The effect of nitrogen fertilizer management on physiological traits of lodging resistance in semi-high-stem hybrid rice with higher biomassWith the increasing of application rate of nitrogen fertilizer, the ability of lodging resistance significantly decreased. The content of total K, total Si, cellulose, lignin and C/N in the stem was gradually decreased with the increasing of application of nitrogen fertilizer; the content of total K and C/N in sheath was on a declining curve, but the total Si showed an upward trend. In general, the effect of application rate of nitrogen fertilizer on C/N was much bigger than other physiological traits, so adjusting the application rate of nitrogen fertilizer to change the plant C/N can regulate the ability of lodging resistance. |
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