Ontogeny and characterization of aerenchymatous tissues of Melastomataceae in the flooded and well-drained soils of a Neotropical savanna

Lavoisiera bergii Cogn., Macairea radula (Bonpl.) DC. and Trembleya parviflora (D. Don) Cogn. are shrubby species of the family Melastomataceae. They occur in the flooded area of the Vereda Grande palm swamp in the Águas Emendadas Ecological Station (a protected area in the midwest of Brazil). M. radula and T. parviflora also occur in the well-drained soil of the cerrado sensu stricto that surrounds the palm swamp. Root and shoot anatomy of the three species show aerenchyma in plants growing in the waterlogged palm swamp area. In the cortex of roots of L. bergii and T. parviflora this aerenchyma develops in a schizo-lysigenous way. Aerenchymatous spaces occur also in the stems. During secondary growth, the phellogen produces an aerenchymatous polyderm. This latter is formed by two cell types, braciform and compact cells, and shows deposition of suberin in the cell walls. In the emerging organs the polyderm does not form gas spaces. The primary aerenchyma is constitutive and occurs also in the root of M. radula and T. parviflora, even when these species are growing in the well-drained soil of cerrado sensu stricto.