Hydraulic redistribution (HR) in plants facilitates bidirectional water transport through the vascular system in response to soil water potential gradients, with implications for ecological facilitation. This study aimed to evaluate the efficacy and results obtained with high-precision weighing lysimeters in detecting HR in olive (Olea europaea L.) using a split-root experimental setup with potted trees. Sixteen pots, each containing half of a plant’s root system, were independently monitored for mass changes to quantify HR between irrigated and water-stressed compartments. The independent weighing of each pair of linked pots was a challenge, but the purpose-built precision lysimeter array effectively isolated weights despite mechanical connections between pot pairs. Results demonstrated measurable water redistribution via roots from irrigated to dry pots, with mass transfer from the irrigated side to the non-irrigated side of the plants, between 10 and 70 g. After irrigation, non-irrigated pots received by HR on average between 3 and 12% of the irrigation water applied in irrigated pots. This furthermore highlighted the potential of the lysimeters for precise quantification of plant-mediated water dynamics. It was observed that HR intensity peaked shortly after irrigation, some hours to one day, and diminished over time, with higher intensity during nocturnal periods or cloudy humid daily conditions of negligible or null evapotranspiration. These findings confirm previous observations with reverse sap flow sensors, now with a different experimental approach, which appears precise but only possible for potted plants, allowing further understanding of HR.
Paço et al. (Tue,) studied this question.