Leaf morpho-anatomical variations in Billbergia elegans and Neoregelia mucugensis (Bromeliaceae) exposed to low and high solar radiation

The morpho-anatomical leaf structure may be directly affected by variations in the environmental conditions to which plants are exposed during development. The “campos rupestres” vegetation (rocky fields) is subjected to several stress conditions and microclimatic variations that result in important adaptations that enable the survival in these environments. In this study, we analyzed the leaf morpho-anatomy of two bromeliads, Billbergia elegans Martius ex Schultes f. and Neoregelia mucugensis Leme, occurring in the rock fields of Itacolomi State Park, southeastern Brazil, and tested for morpho-anatomical variations in response to light conditions. The analysis followed usual techniques in plant anatomy. Both species exhibited variations in the shape of the rosette, leaf color, and size of leaf sheath and blade. Scale density was higher on both leaf surfaces of individuals exposed to high solar radiation. Thickness of the leaf blade, water-storage parenchyma, chlorenchyma, and stomatal density were higher in individuals exposed to low solar radiation, which disagrees with most previous studies and may be related to the environment where these species occur, where water availability is one of the main limiting factors. Our observations point out a need for studies on herb species from xeric environments, which may bring new information on adaptations to these environments.