Leaf morphoanatomical diversity of representative gypsophyte angiosperm lineages from the Chihuahuan Desert

The gypsophytes living in soils high in gypsum, which affects water availability and physiological processes, exhibit a range of foliar strategies to deal with excess Ca and S. These include xeromorphy, succulence, accumulation of large amounts of Ca, S, Mg, and gypsum, as well as calcium-secreting glands. Due to the great richness of species in the gypsum soils of the Chihuahuan Desert and the surrounding areas of the Sierra Madre Oriental, as to which species there is little knowledge of leaf anatomy, the aim of this contribution was to determine the morphological and anatomical diversity of gypsophyte species of various genera covering representative angiosperm lineages and compare this diversity with that of gypsovag or gypsophobe species of those genera from the surrounding areas. The study was conducted in cross-sections and paradermal sections of field-fixed leaves from 48 species of 29 genera belonging to 21 families within 14 orders. We generated comparative tables based on 41 characters among taxonomic groups and among gypsophytes, gypsovags, and gypsophobes. The results show remarkable morphoanatomical diversity among the studied genera and the three groups without statistical differences. The observed xeromorphic characteristics—namely, thickened cuticles and outer periclinal walls, sunken stomata, the presence of trichomes, well-developed palisade tissue, and sheath extensions—are consistent with those reported in species that inhabit nutrient-poor soils with low water availability and high levels of incident light, characteristics of the arid region in which these plants live. Original findings such as the detection of less-reported traits (e.g., vessels arranged in radial rows, gelatinous fibers) and the leaf anatomy for many species studied for the first time, contribute to anatomical knowledge.