CHLOROPHYLL DEVELOPMENT IN MATURE LYSIGENOUS AND SCHIZOGENOUS ROOT AERENCHYMAS PROVIDES EVIDENCE OF CONTINUING CORTICAL CELL VIABILITY

The 'greening' of mature aerenchymatous adventitious roots of Phragmites australis (Cav.) Trin. ex Steudel, rice, maize, Acorus calamus L., and Epilobium hirsutum L., when exposed to light was found to be due to chloroplast development in the cortex. In Phragmites, maize and rice, which are characterized by lysigenous cortical aerenchymas, chloroplasts developed not only in normally intact cortical cell layers adjacent to the exodermis/hypodermis and endodermis, but also in isolated radial cellular strands (and isolated cells) between the lacunae, cells which had failed to collapse during the active phase of aerenchyma development. The observation provides conclusive evidence for the continuing Viability and the potential for active metabolism of the non-lysed cells of lysigenous aerenchymas. In Acorus and Epilobium, chloroplast development occurred in the cells of the schizogenous cortical aerenchymas. In Phragmites, chloroplasts also developed in the non-aerenchymatous cortex of illuminated fine basal lateral roots.