Aerenchyma

Aerenchyma

In botany, the term aerenchyma refers to the parenchymal tissue rich in large intercellular spaces, in which air is stored; it is found in various organs of aquatic or marsh plants, e.g. in the stalk of water lilies, in the stems of rushes, or in the fruits of the water chestnut.
Aerenchyma is therefore a spongy tissue that allows gas exchange between the shoot and the root. Air-filled cavity channels provide a low resistance internal path 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 that need to grow in hypoxic soils.

Many wetland plants possess aerenchyma, and in some, such as water lilies, there is a flow of atmospheric air mass through leaves and rhizomes.
The presence of aereenechima allows plants, which have adapted to grow in wetlands or in water, an internal path with low resistance for the exchange of gases between the organs of the plant above the water and the submerged tissues. This allows plants to grow without incurring the metabolic costs of anaerobic respiration.
Part of the oxygen carried through the aerenchyma escapes through the root pores into the surrounding soil. Furthermore, the small rhizosphere of oxygenated soil around the individual roots supports microorganisms that prevent the influx of potentially toxic soil components such as sulphide, iron and manganese.