The leaf patch clamp pressure probe: A new tool for irrigation scheduling and deeper insight into olive drought stress physiology

Leaf turgor pressure provides a very sensitive indicator of plant water status. Diurnal changes in turgor pressure of olives were measured over several months with a novel leaf patch clamp pressure (LPCP) probe. The LPCP probe is user-friendly, non-invasive, online-monitoring, robust and versatile, and is characterised by high precision, low-cost and automation suitability. Data are transferred wireless to an internet server via a mobile phone network for real-time evaluation and for remote regulation of irrigation or stress management. The probe measures the attenuated output pressure response (P _p) of a leaf patch upon application of an externally applied, constantly kept pressure, generated by two small magnets. P _p is sensed by a miniaturized pressure sensor embedded in silicon and integrated into one of the magnets. Concomitant measurements of balancing pressure values, P _b (i.e. stem water potential) using the pressure bomb technique revealed a very close correlation between P _b and P _p. Both parameters depended inversely on cell turgor pressure as evidenced by direct measurements of leaf turgor pressure using the cell turgor pressure probe. Measurements on olive trees planted in weighing lysimeters that allowed continuous monitoring of water balance of individual trees subjected to varying conditions of water status demonstrated the potential of the LPCP probe for irrigation scheduling and for elucidation of drought stress physiology.