| Heilongjiang Province is an important commodity grain production base and the main producing areas of the high quality japonica rice in China. Improving the yield of japonica rice in Heilongjiang Province is very important for the security of food and energy of our contry. Potassium is the large number of elements which is necessary for plant growth, and it has important nutritional and physiological function. Rice is extremely sensitive to potassium. The Improper potash application in recent years is becoming to one of limitation factors of high-yielding rice. In this thesis, the main variety of Heilongjiang province, Dongnong425, Dongnong427 and Songjing 6 were used as experimental materials, setting seven potassium application rate treatments, K0(0 kg·ha-1), K1(25 kg·ha-1), K2(50 kg·ha-1), K3(75 kg·ha-1), K4(100 kg·ha-1), K5(125 kg·ha-1), K6(150 kg·ha-1). The effects of potassium application rate on SPAD values in functional leaves, functional leaf area index, formation and accumulation of carbohydrate of each organ in the whole stages, key enzymes of carbohydrate metabolism, dry matter accumulation and yield of japonica rice in cold region were studied, revealing the mechanism of the formation and metabolism of carbohydrate and the control effect of potassium on it. The best potassium application rate of japonica rice in cold region can be determined, so as to provide theoretical basis for high-yielding fertilization application of japonica rice in cold region. The main results of this experiment are as follows:1. With the proceeding of growth period, functional leaves’ SPAD values and leaf area index of the three varieties showed a trend of increase, and reached maximum in full heading stage and decreased after that. Functional leaves’ SPAD values and leaf area index of each variety increased as the amount of potassium application increasing in a certain range, but if the amount of potassium application was too large, they decreased. In each growth period, functional leaves’ SPAD values and leaf area index of Dongnong425 and Dongnong427 reached the maximum in K3 treatment, and Songjing 6 reached the maximum in K4 treatment.2. During the whole growth period, sucrose content, fructose content, total soluble sugar content, SPS(sucrose phosphate synthetase), SS(sucrose synthetase) and FBPase(fructose 1, 6-2 phosphatase) enzyme activities in functional leaves of the three varieties in each treatment changed as unimodal curve, and reached to its highest point in milk stage. Before milk stage, sucrose content, fructose content, total soluble sugar content and SPS, SS and FBPase activities in functional leaves increased with the potassium application rate increasing in a certain range, but reduced when potassium application rate reached to a certain extent. Dongnong425 and Dongnong427 reached the maximum in K3 treatment, and Songjing 6 reached the maximum in K4 treatment. From milk stage to ripe stage, sucrose content, fructose content and total soluble sugar content in functional leaves decreased substantially. Treatments with potassium decreased more substantially than the treatment without potassium. Dongnong425 and Dongnong427 had the maximal descend range in K3 treatment, and Songjing 6 had the maximal descend range in K4 treatment. After milk stage, SPS, SS and FBPase enzymes activity in functional leaves decreased, Dongnong425 and Dongnong427 reached the maximum in K3 treatment, and Songjing 6 reached the maximum in K4 treatment. Functional leaves’ sucrose content, fructose content, total soluble sugar content and SPS, SS and FBPase enzyme activity of Dongnong 425 in each treatment were higher than the other two varieties.3. Milk stage and before that, it showed very significant positive correlation between SPS, SS, FBPase activity and the content of soluble sugar content with its components in functional leaves of japonica rice in cold region. In dough stage, SPS, SS activity and sucrose content showed significant positive correlation. SPS, SS activity and fructose content showed very significant positive correlation. SS activity and the total soluble sugar content showed significant positive correlation. FBPase activity and fructose content showed significant positive correlation. In ripe stage, SPS activity and fructose content, soluble sugar content showed significant positive correlation. It showed very significant positive correlation between SS, FBPase activity and fructose content. SS, FBPase activity and total soluble sugar content showed significant positive correlation.4.Sucrose content, fructose content, total soluble sugar content, sugar output rate and contribution rate in stem sheath of japonica rice in cold region changed as unimodal curve during the whole growth stages, and reached the maximum in full heading stage. In each growth stage, sucrose content, fructose content, total soluble sugar content,sugar output rate and contribution rate of the three varieties in stem sheaths increased as the potassium application rate increasing in a certain range, but reduced when potassium application rate higher. Soluble sugar content,sugar output rate and contribution rate in stem sheath of Dongnong 425 and Dongnong 427 reached the maximum in K3 treatment, and Songjing 6 reached the maximum in K4 treatment. Appropriate potassium application rate can promote the accumulation of photosynthetic products and the storage photosynthate redistribution in stem sheath of japonica rice in cold region, it also can provide sufficient substrate for grain-filling. Appropriate potassium application rate can increase rice yield by increasing the grain filling percentage.5. Sucrose content, fructose content and total soluble sugar content in grain of the three varieties began to decline at the 7th day after flowering and decreased to the minimum at the 28 th day after flowering(fructose is at the 35 th day after flowering), and rebounded after that. In the 7th days after flowering, sucrose content, fructose content and total soluble sugar content in grain of Dongnong 425 and Dongnong 427 reached the maximum in K3 treatment, and Songjing 6 reached the maximum in K4 treatment. Within a certain range, increasing potash application can provide adequate substrate for synthesis of grain starch, but more than a certain potash application rate will affect the supply of substrate for synthesis of grain starch. When the 14th–28th day after flowering(fructose is at the 35 th day after flowering), the content of soluble sugar and its components in grains decreased rapidly, and a large number of soluble sugar in grain changed rapidly into starch. Within a certain range, the range of the decreasing of the sugar content in grain increased with the potassium application rate increasing, but it would reduce instead when the potassium application rate increased to a certain degree. Dongnong425 and Dongnong427 had the maximal descend range in K3 treatment, and Songjing 6 had the maximal descend range in K4 treatment.6. With the proceeding of growth period, the dry matter weight of aboveground organ of japonica rice in cold region increased and reached maximum in mature stage. Aboveground dry matter weight of Dongnong 425 and Dongnong 427 reached the maximum in K3 treatment. Songjing 6 reached the maximum in K4 treatment. Within a certain range, dry matter weight in stem sheath, stem sheath material output, output rate and conversion rate of full heading stage and mature stage increased with the increasing of the potassium application rate, but it would reduce instead when the potassium application rate increased excessively. These indexes of Dongnong 425 and Dongnong 427 reached the maximum in K3 treatment, and Songjing 6 reached the maximum in K4 treatment.7. Appropriate potassium application rate can promote the yield of japonica rice in cold region. The yield of Dongnong425 reached the maximum in K3 treatment, which showed no significant difference with K4 treatment, but showed significant difference with other treatments. The yield of Dongnong427 reached the maximum in K3 treatment, which showed no significant difference with K4 and K5 treatment, but showed significant difference with other treatments. The yield of Songjing6 reached the maximum in K4 treatment, which showed significant difference with other treatments. The best K2 O application rate of Dongnong425 and Dongnong427 is 75 kg·ha-1, and the best K2 O application rate of Songjing 6 is 100 kg·ha-1. Japonica rice yield and stem sheath soluble sugar output rate, stem sheath material output rate, stem sheath material conversion rate showed very significant positive correlation. Japonica rice yield stem sheath material and output showed significant positive correlation. |
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