In the previous study, we investigated the alleviation effect of grafting on potassium uptake in roots and tobacco growth inhibition under low potassium stress. However, the effect of grafting on the low potassium stress perception and coping mechanism of tobacco at the whole plant level is not clear now. In order to clearly understand the impact of grafting on potassium deficit responding mechanism in tobacco, a mutual grafting experiment has been conducted in two varieties of tobacco (‘Wufeng No.2’ and ‘Yunyan 87’) in different K supply level (5 mmol L− 1 and 0.5 mmol L− 1 K). The results show that compared with the self-rooted seedlings, grafting significantly increased the potassium content of the whole plant of Yunyan 87 (97.57 and 189.74% under normal potassium and low potassium conditions, respectively), and the increase in shoots was greater. The data of whole plant K content distribution and tobacco hypocotyls net K+ flux demonstrates that potassium stress makes plants more inclined to maintain K+ in the shoot rather than root. In addition, when K deficiency occurs, grafting could reduce the time required for downward net K+ flux in tobacco hypocotyl to decrease to stable levels. The results of net K+ flux in the roots indicated that K channel proteins and transporters play different roles in two rootstocks in terms of potassium tolerance. Transcription level analysis suggested that the increased circulating efficiency of K+ between the shoots and roots in tobacco constitutes one means to low potassium stress adaptation. Grafting can activate more K+ channels in tobacco ‘Yunyan 87’, this means a more active K+ cycle, higher potassium content in shoot and faster response to low potassium stress signals in grafting tobacco. In addition, grafting can also change the K+ absorption mode of tobacco root from being dominated by HATS to being jointly responsible by HATS and LATS, greatly improving the ability of K+ transmembrane transportation on root surface under low potassium stress. These are undoubtedly the reasons why grafting tobacco performs better in coping with low potassium stress.

中文翻译：

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嫁接烟草对低钾胁迫的响应。


在前期研究中，我们考察了低钾胁迫下嫁接对根系吸钾和烟草生长抑制的缓解作用。但嫁接对烟草全株水平低钾胁迫感知及应对机制的影响尚不清楚。为了明确嫁接对烤烟缺钾反应机制的影响，以‘五丰2号’和‘云烟87’两个品种在不同供钾水平（5 mmol）下进行了相互嫁接试验。 L− 1 和 0.5 mmol L− 1 K)。结果表明，与自根苗相比，嫁接显着提高了云烟87全株含钾量（常钾和低钾条件下分别为97.57%和189.74%），且地上部增加幅度更大。全株钾含量分布和烟草下胚轴净钾通量的数据表明，钾胁迫使植物更倾向于在地上部而不是根部维持钾。此外，当发生缺钾时，嫁接可以减少烟草下胚轴中向下的净K+通量降低到稳定水平所需的时间。根部净K+通量结果表明，K通道蛋白和转运蛋白在两种砧木的钾耐受性方面发挥着不同的作用。转录水平分析表明，烟草芽和根之间 K+ 循环效率的提高是适应低钾胁迫的一种手段。嫁接可以激活‘云烟87’烟草更多的K+通道，这意味着嫁接烟草的K+循环更加活跃，地上部钾含量更高，对低钾胁迫信号的反应更快。 此外，嫁接还可以改变烟草根系的K+吸收模式，由HATS主导转变为HATS和LATS共同负责，大大提高了低钾胁迫下根部表面K+跨膜运输的能力。这些无疑是嫁接烟草在应对低钾胁迫方面表现更好的原因。