Fig. 1

Effect of grafting combination and K⁺ supply level on K⁺ distribution in tobacco plants. The tobacco graft combinations included the nongrafted tobacco W (Wufeng No.2) and Y (Yunyan 87) and grafted tobacco Y/W (Y grafted onto W) and W/Y (W grafted onto Y). Different uppercase letters denote significant differences (P < 0.05) under normal K levels (5 mmol L^− 1) in potassium content of whole plant, and lowercase letters indicate significant differences (P < 0.05) under starvation (0.5 mmol L^− 1)