This dataset is in vitro validation of a potassium sensor that will be inserted into a plant stem. The dataset shows the sensitivity and selectivity of the fabricated potassium sensor. The data was obtained by measuring changes in electrical current with an increase in concentrations of the primary ion (K+) and interfering ion (Na+) to extract the sensitivity and selectivity, respectively using a semiconductor parameter analyser. K+ ion sensing data, measured directly inside a plant stem, are absent as the in vivo experiment should be optimised further. Full details about this nonGeographicDataset can be found at https://doi.org/10.5285/89998967-a974-4136-b650-b9af9f9d6969