The adaptability of Euphorbia gypsicola and Euphorbia bungei in gypsum soils of west Semnan, Iran

Euphorbia gypsicola (Euphorbiacea, sect. Pithyusa (is one of the six endemic gypsophyte species in the west of Semnan Province, Iran, and E. bungei (sect. Sclerocyathium) is native to the gravelly calcareous or gypseous slopes in southwest Asia. In this study, the adaptability of these two species and the effect of ecological factors on their morphological, anatomical, and micro-morphological characters in the gypseous habitats of West Semnan were investigated using CCA and RDA analytical methods, Canoco 4.5 software. The micromorphological investigations using SEM showed the surface of the leaf and stem of E. gypsicola has long hairs with an average length of 224.5 μm, and the surface of the leaf and stem of E. bungei is smooth and hairless. The size of stomatal guard cells in E. gypsicola leaves is 17.5 µm long and 10 µm wide on average, compared to E. bungei, with stomata 9 µm long and 3 µm wide, the stomata of E. gypsicola species are bigger and deeper. The presence of small and hairy leaves in E. gypsicola fleshy leaves in E. bungei (13.4 mm in average length and an average 3.8 mm width), as well as gypsum crystals in the leaves of E. gypsicola and in stems of E. bungei, are the factors, that help these two species to adapt to the hot desert climate condition of Semnan. Results indicated that the altitude had the highest effect on the abundance of E. gypsicola. The increase of Na and Mg content in the soil reduced the abundance of both species.