DEVELOPMENT OF AERENCHYMA IN ROOTS AND RHIZOMES OF CAREX-ROSTRATA (CYPERACEAE)

Aerenchyma development in Carex rostrata was studied using light and scanning electron microscopy. Specimens were collected at two locations in southern Finland. Examination showed the beginning of aerenchyma development in the cortex of roots at the distance of 30-45 mm from the apex and it was fully developed at 75-90 mm from the apex. First, schizogenous cavities were formed in the cortex, and the sequence continued with a collapse of tangential cell walls in the cortex, leaving radial strands of cells intact and leading to a structure resembling a cobweb in cross section. In the rhizomes some of the radial cell walls disintegrated in the cortex, resulting in radial rows of cells without any tangential connections. No diaphragms were observed in the rhizome. There were no direct contacts between the gas spaces of the roots and the rhizomes. The significance of aerenchyma for metabolic processes is discussed.