项目组前期研究发现，嫁接西瓜接穗能够反馈调控砧木钾的吸收，但其长距离运输调控信号物质尚不清楚。本项目拟以钾高效吸收野生西瓜和钾低效吸收栽培西瓜为材料，自嫁和正反嫁接构建4种砧穗组合，从根系形态、钾吸收动力学、钾浓度、钾吸收基因表达方面分析不同砧穗组合在正常钾和低钾条件下钾吸收能力的差异，同时利用液质联用和高通量测序技术研究不同砧穗组合叶片、茎韧皮部汁液、根系生长素含量、miRNA和靶基因的表达，与根系吸钾能力进行相关和对比分析，初步确定长距离运输反馈信号物质，然后通过在地上部施用生长素及抑制剂、和通过转化模式植物拟南芥结合嫁接的方式确定接穗反馈调控嫁接西瓜砧木钾吸收的长距离运输信号物质。本申请项目的实施可为调控嫁接西瓜对钾素的吸收提供科学依据，还有助于揭示低钾条件下冠-根间的信号转导机制，丰富园艺植物砧穗互作基本理论，促进嫁接西瓜栽培。

In our previous study, we found that the potassium uptake was feedback regulated by scion in the grafted watermelon, the long distance transport signal subtance remains unclear. In this project, the potassium high uptake wild watermelon and low uptake cultivated watermelon are used as materials. The four graft combinations were established via self-grafting and reciprocal grafting. The difference in potassium uptake ability of different grafting combinations will be analyzed from the root morphology, potassium uptake kinetics, potassium concentration, and potassium uptake gene expression. Meanwhile, the concentration of auxin, as well as miRNA and target gene expression in the leaf, stem phloem sap, and root were measured and were associated and comparative analyzed with potassium uptake ability, the preliminary long distance transport signal can be determined. The long distance transport signal subtance related to the feedback regulation by scion on rootstock potassium uptake in grafted watermelon plants will be further confirmed by application auxin and its inhibitors in the shoot, and genetic transformation and grafting of the model plant Arabidopsis. The implementation of this project will provide the scientific basis for the regulation of potassium uptake in grafted watermelon, and will contribute to clarify the shoot to root signal transduction mechanism under low potassium, as well as improve the theoretical basis of rootstock-scion interaction and promote the cultivation of grafted watermelon.