| In our country, the potassium content of tobacco leaves is generally lower, which restricts the improvement of tobacco leaves' quality and becomes an important factor that limiting the development of our tobacco enterprise. Therefore the question how to improve the potassium content of tobacco leaves has been paid attention to generally by the tobacco circle. This article is directed against the current situation that the shortage of potassium resource and the potassium content of tobacco leaves is lower in our country, proceeded with the difference of potassium efficiency of different tobacco genotypes, so we combined nutrient solution culture, sand culture, soil culture and field test in order to compare the difference of potassium efficiency between 7 relatively typical tobacco genotypes and have chosen four representative genotypes from it for further studied in the aspects, such as the absorption, transportation, accumulation and loss of the potassium, separately. We have studied the mechanism of the difference of potassium efficiency of different tobacco genotypes. The main results of study are as followed:1. In the soil culture experiment without potassium application(content of rapidly available potassium is 64.08mg/Kg), the potassium content of 7 different tobacco genotypes ranged from 0.35% to 1.08%, the adaptibility to potassium stress of different tobacco genotypes was quite different. The range of potassium content in leaves which reached 1.87%-6.52% in potassium treaments indicated that potassium fertilizer application can significantly improve the potassium content in tobacco leaves, while there was significant difference among the absorption and utilization ability of different tobaccogenotypes. Tobacco still could absorb the potassium of fertilizer applied in the soil which had high basic potassium supplying level (the content of rapidly available potassium was 261.81mg/Kg), but different tobacco genotypes were significantly different in potassium absorption. G28 was a potassium-efficiency genotype and TI245 was a potassium-inefficiency genotype.2. The potassium content of the potassium-efficiency genotype G28 was significantly higher than the potassium-inefficiency genotype TI245 in every period of duration. The potassium content of tobacco leaves decreased from early growing stage to late growing stage in potassium treatment, but from late growing stage to ripening stage, the potassium content of G28 increased from 4.36% to 6.52%, it indicated that the difference in potassium absorption and accumulation of different tobacco potassium-efficiency genotype mainly present in late growing stage. .3. The volume, total absorbing surface and active absorbing surface of potassium-efficiency genotype tobacco' roots were significantly higher than those of potassium-inefficiency genotype tobaccos, the potassium-efficiency genotype tobaccos had root morphology feature beneficial to nutrition absorbing. The root active power of potassium-efficiency genotype tobacco was higher than the potassium-inefficiency genotype in different levels of potassium applying treatments, and the root CEC of potassium-efficiency genotype tobacco were relatively high in the condition of higher potassium application. Roots of potassium-efficiency genotype tobacco have better physiology propoties.4. The value of "Imax" of potassium-efficient genotype's root are significantly higher than those of the potassium-inefficiency genotypes and that of "Km" "Cmin" are lower . Therefore the kinetic parameters indicated the different ability and potentiality of potassium absorbing, and "Cmin'' could be regarded as the peculiarity index that could screen for potassium-efficiency genotype tobacco.5. After topping 10 days and 20 days, the potassium content of bleeding sap in stem of potassium-efficiency genotype tobaccos were significantly higher than that of potassium-inefficiency genotype tobaccos. It indicated that the potassium-efficiency genotype tobaccos had higher potassium concentration in xylem and...
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