Bark anatomy of Melastomataceae species in the Brazilian Cerrado, a neotropical savanna

Abstract

The bark (all tissues outside the cambium) is a morphologically diverse and functionally important part of the stem. Outer bark (periderm) has a protective function, and inner bark (secondary phloem) is involved in the long-distance transport. In savannas, the relationship between bark structure, life form and habitat is controversial. We studied the morphology and anatomy of bark of Melastomataceae species with different habits growing at different sites in the Brazilian Cerrado (a neotropical savanna), from well-drained to temporarily or permanently waterlogged soils. Bark samples were processed by standard anatomical techniques. Regarding the outer bark, the species studied are grouped into two main categories: with a single periderm (with nonstratified or stratified phelem) and with multiple periderms, that is, with a rhytidome. Although a formal test has not been carried out in this work to assess the existence of a correlation between the microscopic structure of the periderm and the habit and growth distribution of plants, there seems to be no correlation for most of the species studied here, except for a subshrub species inhabiting waterlogged soils. Sclerified cells, calcium oxalate crystals, and phenolic content are abundant through the secondary phloem. Microscopic bark features are useful to distinguish species.