Amperometic microsensor for measurement of gaseous and dissolved CO2

Strong leaf surface basification and CO2limitation of seagrass induced by epiphytic biofilm microenvironments

“…The length of the pH sensitive glass of the used pH microelectrodes is ~150 μm (Unisense A/S, Denmark) with the highest pH sensitivity across the middle part (i.e., at ~75μm), where the pH glass is thinnest; the operational spatial resolution of the used pH microsensors was thus ~50–150 μm. Novel Clark‐type CO 2 microsensors (tip diameter of 20–100 μm, detection limit <0.5 μM; Revsbech et al, ) were used to measure the CO 2 concentration toward and at the leaf surface. Their 90% response time to a CO 2 increase was ~160 s, while they exhibited a slower response time for a CO 2 decrease of ~12 min, wherefore all CO 2 measurements were done from low to high concentrations depending on light or dark conditions.…”

“…Their 90% response time to a CO 2 increase was ~160 s, while they exhibited a slower response time for a CO 2 decrease of ~12 min, wherefore all CO 2 measurements were done from low to high concentrations depending on light or dark conditions. The novel CO 2 microsensor sensing principle is based on a Clark‐type electrochemical sensor, containing a Ag cathode in an ionic liquid with a guard cathode behind the sensing cathode to prevent interference, both protected via an acidic O 2 trap solution containing Cr 2+ surrounding the electrochemical sensor (see details in Revsbech et al, ). The CO 2 microsensors were linearly calibrated (four‐points) in dinitrogen (N 2 ) preflushed, acidic (pH <4) milliQ water with known CO 2 concentrations (i.e., 0, 37, 74, and 111 μM), obtained by injecting defined volumes of CO 2 saturated water into a defined volume of the milliQ water in a custom‐made calibration chamber kept at experimental temperature.…”

Root O2 consumption, CO2 production and tissue concentration profiles in chickpea, as influenced by environmental hypoxia

“…1a,b) revealed a severely hypoxic core even when in solution with an O 2 concentration at air equilibrium. The new CO 2 microsensor (Pedersen et al, 2018;Revsbech et al, 2019) enabled measurements of CO 2 within roots ( Fig. 1c, d).…”

“…To date, data on presumed CO 2 gradients across roots and the DBL have not been available, as such measurements with high spatial resolution would require a CO 2 -specific microsensor. Here, we report for the first time on radial profiles of CO 2 across roots and within the DBL, measurements made possible by the recent development of a new CO 2 microsensor (Pedersen et al, 2018;Revsbech et al, 2019).…”

“…The present study used a new CO 2 microsensor (Pedersen et al , ; Revsbech et al , ) and an O 2 microsensor (Revsbech, ) to compare spatial profiles of CO 2 and O 2 across roots in aerated or hypoxic conditions, and to conduct simultaneous, nondestructive flux measurements of root O 2 consumption and CO 2 production (and thus RQ) with declining external O 2 . We tested two hypotheses: (1) that, in hypoxic conditions, the vascular cylinder of roots will become severely hypoxic, and CO 2 will show a gradient in the opposite direction to that of O 2 (CO 2 gradient from vascular cylinder > cortex > external medium); and (2) roots exposed to progressive declines in external O 2 supply will show progressive increases in RQ.…”