XVI International Botanical Congess

Production of gas spaces in aerenchyma is a constitutive process in roots of vascular plant species adapted to flooded soils. Light and electron microscopy were used to examine developmental changes from tissue to subcellular levels of root organization. Superficially, gas spaces in mature roots of several wetland species are similar in appearance and are formed by two general mechanisms: the collapse of developing cortex cells and separation of cells during tissue expansion. The relative importance and specific characteristics of these mechanisms, however, vary with species. Variation in these mechanisms apparently produces differences in the rates at which gas spaces are formed. Relationships among patterns of cell collapse, cell separation and rate of gas space formation in roots of different species will be discussed.