Measurement of Radial Oxygen Loss

A wide range of techniqnes are nsed to docnment and qnantify oxygen release by wetland plants, inclnding 

Oxygen microelectrodes, similar to those described by Revsbech (1989), have been used to determine the ROL and thickness of aerobic layers around the roots. Oxygen-depleted hydroponic soln-tions used in many ROL experiments are, however, a poor analog of wetland soil, because they do not mimic the high oxygen demand and low redox potentials found in wetland soil (DeLanne et al., 

Sediment oxygen demand acts as a sink for oxygen released by roots. 

FIGU RE 7.23 (a) Redox potential in the rhizosphere of Ranunculus circinatus at three electrode positions, El 

Absorbance of the partly oxidized TF+-citrate solution is measured at 527 nm on a U 7V1S spectrophotometer. Released oxygen on a whole-plant basis is determined by extrapolation of the measured absorbance to a standard calibration curve. These hydroponic studies using artificial redox buffer may be useful in screening related response of wetland plants to reduced soil conditions. However, the conditions do not truly mimic the conditions in wetland soils. Oxidation of other reductants such as DOC, ferrous iron, and ammonium can also be used to estimate oxygen transport capacity of wetland plants (Reddy et al., 1990 Burgoon and Reddy, 1996). 

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