A biomineral is a crystalline or amorphous mineral product of the biochemical activity of an organism and the local accumulation of elements available in the environment. The cactus family has been characterized by accumulating calcium oxalates, although other biominerals have been detected. Five species of Cacteae were studied to find biominerals. For this, anatomical sections and Fourier transform infrared, field emission scanning electron microscopy and energy dispersive x-ray spectrometry analyses were used. In the studied regions of the five species, they presented prismatic or spherulite dihydrate calcium oxalate crystals, as the predominant biomineral. Anatomical sections of Astrophytum asterias showed prismatic crystals and Echinocactus texensis amorphous silica bodies in the hypodermis. New findings were for Ariocarpus retusus subsp. trigonus peaks assigned to calcium carbonate and for Mammillaria sphaerica peaks belonging to silicates.

Generic circumscription and species relationships in several lineages in Cactaceae tribe Cacteae remain unresolved. Turbinicarpus s.l. is one of the most species-rich genera in Cacteae, with its centre of distribution in the Chihuahuan Desert, Mexico. We reconstructed a phylogenetic tree of Turbinicarpus s.l. with Bayesian inference, using plastid DNA sequences and morphological characters, and inferred biogeographic history in order to understand their relationships. Our results supported the recognition of three different monophyletic lineages: Kadenicarpus, Rapicactus and Turbinicarpus. Kadenicarpus is endemic to the southernmost part of the Chihuahuan Desert in the states of Hidalgo and Querétaro. Rapicactus and Turbinicarpus are distributed in the main region of the Chihuahuan Desert where they have areas of overlap.

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Background: The genus Coryphantha has the second largest number of species of the tribe Cacteae-Cactaceae. Morphologically, it has been reported that the stem presents mainly globose, ovoid and cylindric variations. However, at the anatomical level, descriptions are scarce and focused on particular tissues (epidermis or xylem). The aim of this work is to contribute to the anatomical knowledge of the genus. Questions and/or Hypotheses: What are the anatomical characteristics that differentiate one species from another? Does the presence of crystals allow differentiation between species? Study species: Coryphantha clavata , Coryphantha cornifera and Coryphantha radians . Site and years of study: San Luis Potosí and Querétaro, Mexico; 2017, 2020. Methods: Three individuals per species were collected, and conventional histological techniques were applied. Anatomical descriptions were made for different tissues, and structural characteristics were measured for each species. Results: The species exhibited the greatest differences in the epidermis and hypodermis, such as the presence of subepidermal stomata ( C. radians ), three-layered hypodermis ( C. clavata ), and non-collenchymatous hypodermis ( C. cornifera ). Crystals were not observed in the epidermises but instead in the hypodermes, which exhibited crystal shapes of druses ( C. cornifera and C. radians ), prisms and round bodies ( C. clavata ). In the cortical tissue, C. clavata had abundant mucilage cells. The observed xylem and phloem tissues exhibited characteristics similar to those of other Coryphantha species. Conclusions: The anatomical characteristics of the epidermis and hypodermis are considered of high systematic value and could be used to distinguish between species of the genus.

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