[Objectives] In order to understand the mechanism of high efficient absorption of potassium in tobacco,and to provide reference for selecting potassium-enriched flue-cured tobacco,the potassium metabolism characteristics of flue-cured tobacco varieties at the maturity were studied.[Methods] The potassium-enriched flue-cured tobacco cultivar ND202 and conventional cultivars,K326 and NC89,were selected,and a pot experiment was carried out.Changes of soil available potassium contents in non-rhizosphere and rhizosphere,physiological characteristics of roots,potassium accumulation in different parts of tobacco,and potassium channel and transporter gene expression at the mature stage were analyzed.[Results] The potassium accumulation of ND202 mature leaves was significantly higher than those of K326 and NC89,but the differences among the cultivars were not significant in roots and stems.The potassium accumulation of whole plant of ND202 was the highest,reaching to 10.18 g/plant and was 109.90％ and 90.28％ higher than those of NC89 and K326,respectively (P ＜ 0.05).At the mature stage,the average root fresh weight and root volume of ND202 were significantly higher than those of K326,and root vigor was significantly higher than that of NC89.The rhizosphere soil available potassium content of ND202 at the rosette and vigorous growing stages was significantly lower than those of NC89 and K326 respectively,and significantly lower than those of NC89 and K326 at the maturity stage.The non-rhizosphere soil available potassium of ND202 was significantly higher than those of NC89 and K326 at the mature stage.The relative expression levels of inner flow potassium channel gene NKT1 and NtKC1 varied among cultivars and parts at the mature stage.The expression of NKT1 in the upper leaves of ND202 was significantly higher than that in K326 and NC89,the relative expression of NtKC1 in roots,upper and middle leaves was significantly higher than that of NC89 and K326,and the relative expression of potassium channel gene NtTPK1 was significantly higher than NC89 and K326 in the root and middle leaves,which was beneficial to the absorption of potassium ions.The relative expression of effiux potassium channel gene NTORK1 of ND202 in the lower leaves was significantly lower than that of NC89 and K326,and the less potassium effiux was favorable to the increase of potassium content.The relative expression levels of potassium transporter gene NtHAK1 and NtKT12 in different parts and different cultivars were different.The relative expression of NtHAK1 in roots and upper leaves and middle leaves,and the relative expression of NtKT12 in roots and upper leaves of ND202 were significantly higher than those of K326 and NC89,which was beneficial to potassium translocation and accumulation.[Conclusions] Potassium-enriched flue-cured tobacco ND202 has characteristics of developed root system,higher root absorption ability,higher relative expression of potassium ion channel and transporter gene,and larger amount of potassium accumulation in leaves at the mature stage.%[目的]研究富钾烤烟品种成熟期钾素代谢特征,有助于了解烟草高效吸收钾的机理,为富钾烤烟基因型的筛选提供参考依据.[方法]选用富钾烤烟品种ND202和常规品种K326、NC89进行盆栽试验,分析了不同烤烟品种生长过程中非根际和根际土壤速效钾含量的变化,成熟期根系生理特性差异,成熟期不同部位钾积累量、钾离子通道和转运体基因表达差异.[结果]富钾品种ND202成熟期叶片中的钾积累量极显著地高于K326和NC89,茎和根中的钾积累量品种间差异不显著,ND202全株钾积累量最高,达到10.18 9/株,分别比NC89和K326高109.90％和90.28％,差异达极显著水平.成熟期ND202的平均根鲜重和根体积显著高于K326,根系活力显著高于NC89.ND202根际土壤速效钾含量分别在团棵期极显著低于NC89,在旺长期极显著低于K326,在成熟期极显著低于2个品种,非根际土壤速效钾在成熟期极显著高于NC89和K326.成熟期内流型钾离子通道基因NKT1和NtKC1在不同品种不同部位的相对表达量不同,ND202上部叶中的NKT1表达量显著高于K326和NC89,根、上部叶和中部叶中NtKC1的相对表达量极显著高于NC89和K326,ND202的钾离子通道基因NtTPK1在根、中部叶中极显著高于NC89和K326,有利于钾离子的吸收;ND202下部叶中外流型钾离子通道基因NTORK1的相对表达量极显著低于NC89和K326,钾素外排较少有利于钾含量的提高;钾转运体基因NtHAK1和NtKT12在不同品种不同部位的相对表达量不同,ND202在根、上部叶和中部叶中NtHAK1的相对表达量,在根和上部叶中NtKT12的相对表达量均极显著地高于K326和NC89,有利于钾素运转和积累.[结论]富钾品种ND202具有成熟期根系较发达,根系吸收能力较强,钾离子通道和转运体基因相对表达量较高,叶片中钾积累量较大的特征.
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