aerenchym

Aerenchyma is a plant tissue characterized by extensive intercellular air spaces within parenchyma, forming networks that connect leaves, stems, and underground organs. This structure is especially common in aquatic and waterlogged plants, including many grasses, reeds, aquatic angiosperms, and other wetland species. The air-filled spaces facilitate gas diffusion between photosynthetic tissues and roots, enabling oxygen to reach submerged roots in hypoxic soils and allowing the exchange of other gases as needed.

Aerenchyma develops mainly by two processes. In lysigenous aerenchyma, certain cells die and degenerate, leaving large lacunar spaces. In schizogenous aerenchyma, spaces form by separation and expansion of cell walls without cell death. Some species exhibit a combination of both forms (schizolysigenous). Formation is often stimulated by low oxygen conditions and plant hormones such as ethylene, which promote programmed cell death and tissue remodeling.

Functionally, the primary role of aerenchyma is to enhance internal gas exchange. By creating continuous air channels, it delivers oxygen from shoots to submerged roots and rhizomes, supporting aerobic respiration in flooded soils. Aerenchyma can also contribute to buoyancy in certain aquatic plants and may provide short-term air storage. Ecologically, it supports survival, growth, and productivity in wetlands and flood-prone habitats and can influence the distribution of aquatic and semi-aquatic plant communities.