Anatomy and foliar architecture of two Mexican species of Ternstroemia Mutis ex L.f. (Pentaphylacaceae)

Abstract

Background: Many Mexican Ternstroemia species mainly inhabit the tropical montane cloud forest. These species have been misidentified in herbaria due to their morphological resemblance. Question: Are there foliar anatomical and micromorphological characters with diagnostic value that allow discriminating between the Mexican species of Ternstroemia? Study species: Ternstroemia sylvatica Schltdl. & Cham., and T. lineata DC. subsp. lineata (Pentaphylacaceae Engl.), 2018-2019. Study site and date: Tropical montane cloud forests at the Trans-Mexican Volcanic Belt and Sierra Madre Oriental. Methods: Botanical specimens were collected and removed from herbarium sheets. The leaves were prepared through cleared, dehydration and paraffin inclusion techniques to observe and describe them. Results: The Ternstroemia species showed specific features of plants in humid environments, such as thin cuticle, mesophyll with scarce parenchyma palisade, and abundant intercellular spaces in the spongy parenchyma, and specific pigments that help to capture light and serve as protection. The species share a festooned broquidodromous venation pattern, anomocytic stomata, and closed collateral vascular bundle surrounded by perivascular fibers. Both species are differentiated by leaf shape, abundance of collenchyma layers, lenght of palisade parenchyma, and number of stomata per square millimeter on the abaxial surface. Conclusions: We support and validate some features recorded for Ternstroemia species and reject some previous generalizations made worldwide to the genus. This research is the first attempt to study anatomy, architecture, and foliar micromorphology of Mexican Pentaphylacaceae.