Definition: Tissues with large intracellular spaces that provide buoyancy. An air channel in the roots of some plants, allows exchange of gases between the shoot and the root. The channel of large air-filled cavities provides 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 form in roots subject to anoxia such as what occurs during flooding of plants and soil.


During drought, aerenchymas allow plant roots to grow deeper for water, even through compacted layers; thick and tough roots are formed. As the roots die back and decay, the resulting voids are paths in which new roots can grow and elongate when resources are available.