Sofía Loza-Cornejo

Epidermal and hypodermal characteristics in North American Cactoideae (Cactaceae)

Abstract.Dermal and hypodermal anatomical features of 70 species representing 21 genera of North American Cactoideae were studied. Results show that all species examined have parallelocytic stomata and anticlinal wall surface varies from straight to undulate. Cuticle thickness is mostly narrow (1–10xa0µm) contrary to the general opinion that cuticle is thick in most cacti; however, few species such as Ariocarpus fissuratus and several species of Pachycereus show a distinctive thick cuticle. More than 80% of the species studied have a single-layered epidermis. Papillae occur in eight species belonging to four genera. Notable papillae are a feature shared by all members of Peniocereus subg. Peniocereus. Other species show a bullate surface produced by irregular patches of secondary epidermal cell divisions. Commonly, the hypodermis is composed of more than two cell layers with distinctive collenchymatous walls as reported in many South American species. Silica bodies, prismatic crystals, druses, sphaerocrystals, and tannins are the most common cellular inclusions that distinguish several genera and appear to have taxonomic value. However, a more thorough search in species of Cephalocereus, Coryphantha, Echinocereus, Mammillaria, Neobuxbaumia, Pilosocereus, and Turbinicarpus is needed to support the previous assertion.

Anatomy of relictual members of Subfamily Cactoideae, IOS Group 1a (Cactaceae)

Summary: n The anatomy of IOS Group la (part of Leptocereeae and part of Echinocereeae) was examined to determine if these genera have characters that are relictual in Cactoideae. Echinocereus lacks fibrous wood and seemed distinct from genera with fibrous wood, which constitute the majority of Group la. Excluding Echinocereus and other genera with non-fibrous wood, Group la has many features presumed to be relictual: epidermal cells with ordinary shapes and thin walls, a tendency to have patches of multiseriate epidermis, hypodermis of a few layers with walls of medium thickness, cortical bundles with caps of primary phloem fibers but lacking clusters of terminal tracheids, presence of medullary bundles (and these have xylary fibers), fiber caps next to primary phloem of the stele, presence of fibrous wood and lack of any derived wood types. Derived characters that do occur are not universally present or even widespread in the group. Little evolutionary modification has occurred in Group la, except for Echinocereus.

Raman Spectroscopy Study of Calcium Oxalate Extracted from Cacti Stems

To find markers that distinguish the different Cactaceae species, by using near infrared Raman spectroscopy and scanning electron microscopy, we studied the occurrence, in the stem, of solid deposits in five Cactaceae species (Coryphantha clavata, Ferocactus latispinus, Opuntia ficus-indica, O. robusta, and O. strepthacantha) collected from their natural habitats from a region of México. The deposits in the tissues usually occurred as spheroidal aggregates, druses, or prismatic crystals. From the Raman spectra, the crystals were identified either as calcium oxalate monohydrate (CaC2O4H2O) or calcium oxalate dihydrate (CaC2O4·2H2O) Opuntia species (subfamily Opuntioideae) showed the presence of CaC2O4·H2O, and the deposition of CaC2O4·2H2O was present in C. clavata and F. latispinus (subfamily Cactoideae, Cacteae tribe). As a punctual technique, Raman spectroscopy seems to be a useful tool to identify crystal composition. In addition to allowing the analysis of crystal morphology, this spectroscopic technique can be used to identify Cactaceae species and their chemotaxonomy.