Abstract: In order to investigate the relationship between potassium nutrition and nitrogen absorption and assimilation ability of flue-cured tobacco, and make clear the possible pathway of interaction between potassium nutrition and nitrogen assimilation, so as to provide a theoretical basis for rational application of potassium fertilizer, this paper took flue-cured tobacco K326 as experimental material, and analyzed the changing of nitrogen and dry matter accumulation in different plant organs, root morphology, root NO-3 absorption rate and root nitrate reductase (NR) activity after potassium deficiency under nutrient solution culture condition. The result showed that dry matter accumulation in stems and leaves decreased significantly under potassium deficiency condition, but there was no significant change in dry matter accumulation of root system. Potassium deficiency shortened the total root length, and reduced root surface area and root volume, but the average root diameter did not change much. Potassium deficiency brought down the nitrogen accumulation in stems and leaves, increased the N allocation rate in root system and decreased the N allocation rate in stems. Potassium deficiency increased the root NO-3 absorption rate, thus the NR activity in root system was significantly increased. In conclusion, the main reason for the decrease of nitrogen accumulation in flue-cured tobacco under potassium deficiency is that the reducing of plant nitrogen demand due to the decrease dry matter accumulation.

Key words: potassium deficiency, root system morphology, nitrogen absorption, nitrogen assimilation

摘要： 为探明烤烟钾素营养与氮吸收同化能力的关系，明确钾素营养与氮同化互作的可能作用途径，为合理施用钾肥提供理论基础，以烤烟品种K326为试验材料，分析了营养液培养条件下，缺钾后烟草各器官干物质和氮积累量的变化情况，根系形态及根系氮硝酸盐吸收速率和硝酸还原酶活性的变化情况。结果表明，缺钾后烤烟茎和叶片的干物质积累量降低，根系干物质积累量无显著变化；缺钾降低了烤烟总根长、根系体积和根表面积，根平均直径无显著变化；缺钾降低烤烟茎和叶片中的氮积累量，增加氮在根系中的分配，降低在茎中的分配；缺钾处理后根系硝酸盐吸收速率和硝酸还原酶活性显著增加。综上，缺钾后烤烟氮积累量降低的主要原因是由于干物质积累量减少导致植物氮需求减少。

关键词: 缺钾, 根系形态, 氮吸收, 氮同化