ANATOMICAL RESEARCHES ON THE OVERGROUND VEGETATIVE ORGANS OF SAXIFRAGA MUTATA L. SUBSP. DEMISSA (SCHOTT & KOTSCHY) D.A. WEBB AND SAXIFRAGA PANICULATA MILLER

This paper presents the structure of the flowering stem, the rosette and cauline leaves of Saxifragamutata L. subsp. demissa (Schott & Kotschy) D.A. Webb and S. paniculata Miller. The vegetal material was collected from Bucegi Natural Park. The structural features of the aerial vegetative organs are correlated with the environmental conditions of these plants. The flowering stem of S. mutata subsp. demissa has sclerenchymatous sheaths around the isolated vascular bundle as well as around groups of two or three vascular bundles. The flowering stem of S. paniculata presents some supplementary collateral vascular bundles among the initial bundles as a result of the enlarging of the stem. We observed isolated phloem groups among the collateral vascular bundle in the flowering stem of both plants. There is a multilayered sclerenchymatous pericycle with a mechanical role in the plants in the flowering stem of both analysed taxa. The presence of the tracheid hydathodes in the rosette and cauline leaves of S. mutata subsp. demissa and S. paniculata is an adaptation to the high temperature on the limestone rocks in the subalpine and alpine areas. The existence of the endodermis (with Caspary strips in S. mutata subsp. demissa) and the monolayered parenchyma pericycle around the vascular bundle in the leaf structure makes the foliar vascular bundle similar to a monobundled central cylinder. The flowering stem and the cauline leaf have multiseriate glandular hairs and a few multiseriate and uniseriate non-glandular hairs. The rosette leaves are hairless. The leaves are amphistomatic, with anomocytic stomata in S. mutata subsp. demisa and tetracytic in S. paniculata.