See Box 11.1 . It may also be an energy spill-over system, when the main electron flow path is saturated. Read p 304-305 for info on alternate oxidase. O 2 in air-equilibrium solution. Situation becomes worse in hydroponic solution or flooded soils.
Respiration is temperature dependent.
Still debated - not always seen. Water replaces soil air - reduces O2 diffusion. Results in fermentation. Pneumatophores, aerenchyma, lacunae, in flood-tolerant species. Increased activity of O 2 -consuming enzymes, e.g. polyphenol oxidase, peroxidase, lipoxygenase that cause browning in apples, potato etc as cutting allows them to come into contact with substrates.