Electrical bioimpedance spectroscopy as a tool for non-destructive monitoring nitrogen supply in two lettuce genotypes

• Bioimpedance spectroscopy parameters can reveal N supply of leaf. • Apoplastic fluid resistance decreased with leaf nitrate content. • A significant relationship was found between vacuole fluid resistance and leaf nitrate content.Cell membrane capacity correlates with membrane stability index. Accurate monitoring of nutrient supply is crucial for effective plant nutrition management. This study introduces a bioimpedance spectroscopy (BIS) approach to evaluate how lettuce genotypes respond to nitrogen (N) supply, illuminating the link between BIS and N metabolism. The research consisted of two parts: a preliminary experiment focusing on extracellular fluid resistance, followed by a second experiment involving five different N treatments applied to two lettuce genotypes. BIS spectra were recorded from 1 Hz to 100 kHz, with a total of 224 measurements. Plant physiological analyses assessed total and extracellular fluid nitrate (NO 3 − ) concentrations, pigment concentration, total N content, and cell membrane stability index. In the preliminary experiment, a significant negative correlation was observed between extracellular fluid NO 3 − concentration and extracellular fluid resistance (r = – 0.67). Furthermore, the frequency range around 63 Hz (R 2 = 0.97) appeared most sensitive to NO 3 − dynamics in the ‘Kobak’ lettuce genotype. In the two lettuce genotypes exposed to the five different N treatments, extracellular fluid resistance negatively correlated with total N and NO 3 − content ( r = – 0.76 and – 0.73), while vacuole fluid resistance showed a moderate correlation ( r = – 0.51). Cell membrane capacitance was also significantly correlated with membrane stability index ( r = 0.68), indicating that low-N conditions reduce membrane charge storage. However, these correlations appeared highly genotype dependent. Heatmap-based hierarchical clustering of Z-score standardized BIS parameters further confirmed these genotype-specific patterns. Collectively, these findings suggest that BIS captures key aspects of N uptake and storage, particularly in the extracellular fluid compartment. Overall, BIS offers a robust, non-destructive method for monitoring N status and may enhance precision in nutrient management for lettuce and other crops, although the genotype-specific differences must be carefully considered.