Redox Potential

When the amount of oxygen in the environment declines the redox potential falls and reduction reactions become more likely. This potential is measured in millivolts (mV).

At +350mV the redox potential is considered "neutral". This is the point at which oxygen is just as likely to be "reduced" to water (H₂O) as it is to oxidized to gaseous oxygen (O₂).

At lower redox potentials the following reactions important to the biochemistry of plants tend to occur:

below +350mV O₂ --> H₂O
below +220mV NO₃^- --> NO₂^-, N₂, and NH₄⁺
below +200mV Mn⁺⁴ --> Mn⁺²
below +120mV Fe⁺³ --> Fe⁺²
below -150mV SO₄^-2 --> H₂S
below -250mV CO₂ --> CH₄

below +350mV		O₂ --> H₂O
below +220mV		NO₃^- --> NO₂^-, N₂, and NH₄⁺
below +200mV		Mn⁺⁴ --> Mn⁺²
below +120mV		Fe⁺³ --> Fe⁺²
below -150mV		SO₄^-2 --> H₂S
below -250mV		CO₂ --> CH₄