aerenchyma

Aerenchyma refers to spaces or air channels in the leaves, stems and roots of some plants, which allows exchange of gases between the shoot and the root.

The channels of air-filled cavities provide a low-resistance internal pathway for the exchange of gases such as oxygen and ethylene between the plant above the water and the submerged tissues. Aerenchyma is widespread in aquatic and wetland plants which must grow in hypoxic soils.