Anatomy of vegetative organs of Lycopodiella cernua (L.) Pic. Serm. and Selaginella biformis A. Braun ex Kuhn

Abstract

This study examines the anatomical structures of vegetative organs in two Lycophyte species—Lycopodiella cernua (L.) Pic. Serm. and Selaginella biformis A. Braun ex Kuhn—based on six specimens collected from Cat Ba National Park and Phong Dien Nature Reserve (Hue). Using established morphological methods and double-staining techniques, we analyzed root, stem, and leaf anatomy to explore evolutionary adaptations in early diverging vascular plants. L. cernua exhibited primitive features, including a mixed protostele in both roots and stems, undifferentiated endodermis, and simple leaves lacking clear mesophyll differentiation. In contrast, S. biformis showed more derived traits: a well-defined endodermis with Casparian strips, exarch protostele in roots, and polystelic stems with trabeculae. Its leaves displayed a dorsiventral structure, chloroplasts confined to the upper epidermis, and stomata on the lower surface, along with a flattened lamina and large intercellular spaces. These anatomical differences suggest that S. biformis has evolved structural specializations that enhance water conduction, photosynthesis, and mechanical support, compared to the more ancestral organization in L. cernua. The findings contribute valuable data to the anatomical database of Lycophytes and offer insights into the evolutionary transitions of vascular tissues in seedless plants. Moreover, the study provides additional evidence for species-level anatomical adaptations within Lycophytes, highlighting their evolutionary strategies for survival in both xeric and mesic environments. The comparative data between genera also serves as a useful reference for future taxonomic, ecological, and evolutionary research in Lycophyta.