Diversity, Leaf Anatomy, and Conservation of Fabaceae in a Thai Limestone Area

Fabaceae, the third-largest family of angiosperms, occurs in diverse habitats, including limestone areas characterized by karst landscapes, and in Thailand, by frequent human disturbance due to activities such as agriculture and mining. These disturbances affect plant species, which highlights the importance of diversity studies and the use of morphology and anatomy for identification. A study of Fabaceae diversity in a limestone area in Thung Song District, southern Thailand, were conducted along three survey routes. A total of 23 genera and 30 species were encountered, including 2 vulnerable, 1 rare, and 8 introduced species. Morphological, phenological, ecological, and conservation status data were recorded. The leaf epidermis of 23 species was observed under a light microscope. Stomatal size and stomatal index were measured. Phanera tubicalyx, an endemic and vulnerable species restricted to limestone habitats, had multiple papillae on its epidermal cells, which may reduce water loss and enhance photosynthetic efficiency. Both hypostomatic and amphistomatic leaves were observed. Stomatal size ranged from 114.63 ± 17.57 μm2 to 608.88 ± 16.42 μm2, while the stomatal index varied from 0.85 ± 0.78 to 23.86 ± 0.16. Peculiar paired crystals and multiple papillae were found in Canavalia cathartica and P. tubicalyx, respectively. These and other morphological and leaf epidermal characteristics were useful for species identification. Human disturbances from agriculture and mining were common in the study area. In conclusion, this study documented 30 Fabaceae species and demonstrated the usefulness of morphological and leaf epidermal characteristics for species identification and conservation.