Aerenchyma

[2] The channels of air-filled cavities (see image to right) provide a low-resistance internal pathway for the exchange of gases such as oxygen, carbon dioxide and ethylene between the plant above the water and the submerged tissues.

Many wetland plants possess aerenchyma, and in some, such as water-lilies, there is mass flow of atmospheric air through leaves and rhizomes.

For example, nitrification is inhibited as low oxygen occurs and toxic compounds are formed, as anaerobic bacteria use nitrate, manganese, and sulfate as alternative electron acceptors.

[8] The reduction-oxidation potential of the soil decreases and metal oxides such as iron and manganese dissolve, however, radial oxygen loss allows re-oxidation of these ions in the rhizosphere.

[10] The large air-filled cavities provide a low-resistance internal pathway for the exchange of gases between the plant organs above the water and the submerged tissues.