Anatomical specificities of two paleoendemic flowering desiccation tolerant species of the genus Ramonda (Gesneriaceae)

摘要

Highlights ? Sinuously folded axial vascular bundles indicate longitudinal compression of the stem. ? Specific organization of vascular tissues contributes to efficient water transport. ? The role of specific ‘vascular sclerenchyma’ in the stem for now remains unclear. Abstract Ramonda serbica and R. nathaliae are known as resurrection flowering plants. Both species are long-living chasmophytes that are physiologically inactive during warm summer periods. Besides numerous known adaptations at the physiological level, it is reasonable to expect that these plant species possess a number of distinctive structu