A microsensor for direct measurement of O2 partial pressure within plant tissues

Abstract

Widespread use of O2 microsensors to measure O2 partial pressure (pO2) in plant tissues has been limited in part because of difficulty of construction and other technical obstacles. By modifying published techniques, an O2 microsensor was constructed that combined the advantages of Clark-type microsensors with less complicated construction techniques. The specifications and some performance characteristics of the microsensor are: tip diameter 1-5 μm; sensitivity 7.5-25 pA kPa-1; negligible stir-induced current; response time 540 ms. The microsensor can be used in air or solution, and each sensor can be used for several experiments. The sensitivity of the microsensor was unchanged during measurements over the physiological range of p02 in intact, growing maize (Zea mays L.) primary roots, and was thus unaffected by cellular fluids and turgor pressure. Use of the microsensor to compare p02 profiles in vermiculite- and solution-grown roots is described. The O2 microsensor could find application in studies in which information on tissue p02 is needed, but for which conventional O2 probes are too large.