Stem and root anatomy of two species of Echinopsis (Trichocereeae, Cactaceae)

Resumen

This study aimed to characterize and compare the stem and root anatomy of Echinopsi calochloraand E. rhodotricha (Cactaceae) occurring in the Central–Western Region of Brazil, in Mato Grosso do Sul State. Three individuals of each species were collected, fixed, stored and prepared following usual anatomy techniques, for observation in light and scanning electronic microscopy. All species revealed uniseriated epidermis, thick cuticle, parallelocytic stomata at the epidermis level, and well-developed hypodermis. Cortical and medullary bundles are present in the studied species, as well as mucilage cells in the cortex region. The secondary phloem is composed by sieve tube elements, companion cells, axial and radial parenchyma. Sclereids were found at the outer regions of phloem in roots. The secondary xylem is non fibrous in the stems of E. calochlora, and fibrous in the stems of E. rhodotricha and in the roots of both species. Many of these characteristics are commonly mentioned for Cactaceae species, representing important adaptations for survival in xeric environments.