Stem anatomy of Turbinicarpus s.l. (Cacteae, Cactaceae) and its contribution to systematics

Abstract

The stem anatomy of Turbinicarpus s.l. was studied with the aims of finding characters to support the three clades (Rapicactus, Kadenicarpus, and Turbinicarpus) in which Turbinicarpus s.l. was recovered in the most recent phylogeny of the Cacteae tribe. Thirty-five taxa were prepared, and their tissues were compared. Substantial variation was found in the epidermal surface. The hypodermis has concentric druses (Rapicactus clade) or prismatic crystals (Kadenicarpus and Turbinicarpus clades) in the cell lumina. There are abundant collateral cortical bundles, but they are amphicribal in a few taxa, and xylary fibers occur in the Kadenicarpus clade. All members of Turbinicarpus s.l. have phloem without sclerenchyma and nonfibrous wood, except for T. subterraneus, which has wood with few fibers. The periderm has an epidermal origin, and the phellem may have thin-walled cells or alternating thin- to thick-walled layers. Our results support the three clades. The Kadenicarpus clade comprises the species with xylary fibers in cortical bundles, but it shares prismatic crystals in the hypodermis, thin-walled phellem cells and partially dilated rays with the Turbinicarpus clade. The members of the Rapicactus clade have concentric druses in the hypodermis. The anatomical features proved to be valuable to support the recognition of monophyletic clades.

Keywords:

• Kadenicarpus
• Rapicactus
• concentric druses
• prismatic crystals
• hypodermis
• nonfibrous wood
• nonconductive phloem variation
• periderm

Acknowledgments

We are grateful to JB-UNAM for the plants donated for this study especially to Omar González Zorzano and Jerónimo Reyes to Berenit Mendoza for SEM technical assistance, and Julio César Montero-Rojas for artwork. We also thank the suggestions of three anonymous reviewers, which improved this manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Funding was provided by the Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica, DGAPA, Universidad Nacional Autónoma de México Project IN209012 and IN224307 to TT.