The anatomical and micromorphological properties of endemic species to gypsic soils of Semnan, Iran.

The gypsum habitats of Iran are significant reserves of biodiversity containing endemic and rare species. Despite the limited understanding of its characteristics and habitat, it has become essential to study the endemic species of the Semnan gypsic soil. Fresh samples of studied species including Acantholimon cymosum, Astragalus fridae, Astragalus semnanensis, Euphorbia gypsicola, Gypsophila mucronofolia, Moltkia gypsaceae and Nepeta eremokosmus were collected in the wild during the growth season. Leaf surface and leaf cross-sections were considered. The longest hair length was related to A. fridae, A. semnanensis and M. gypsaceae species. The shorter hairs belong to the species A. cymosum, G. mucronofolia and E. gypsicola. Crystals called cystolites were seen in the epidermal cell wall of A. semnanensis leaves. The anatomical characteristics of these species' leaves indicate the presence of dry structures. Using micromorphological studies, we analyzed the hairs of the studied species in terms of their shapes, sizes, and densities. We found some species have hairs with special appendages, which is due to the special conditions in which they have grown. Xeromorphic stomata were found on both leaf surfaces of all endemic gypsophyte plants of Semnan. Several studies have shown that gypsophytes have a specialized mechanism for regulating the absorption of sulfur and calcium from soils containing calcium sulfate or gypsum by their roots. The current study provides novel insights into the response of plant species to extreme conditions and potential adaptation strategies at micromorphological levels.