Structural adaptation and anatomical convergence in stems and roots of five plant species from a “Restinga” sand coastal plain

Abstract

Coastal areas present limiting environmental conditions, such as high soil salinity, intense winds, elevated temperature and coastal flooding, which may be related to adaptive anatomical characters. This study aims to evaluate the anatomy of the stems and roots of Restinga plants (eudicots: Blutaparon portulacoides, Canavalia rosea, Ipomoea pes-caprae and Scaevola plumieri; monocot: Remirea maritima) and their relationship to parameters of the microenvironment. These five species were selected because they are dominant and present great occurrence in Restinga vegetation nearest to the sea. Stems and roots of five species (n = 5) were fixed and submitted to standard techniques for analyzing under light microscope. Wind velocity, air temperature, air relative humidity and evaporation level were evaluated close to individuals and above them. The nutritional conditions from rhizosphere were also estimated. The winds were weak close to individuals, while the temperature was higher than compared to measurements above individuals. Minor differences of the soil were noted between areas close and far from the plants. Seven anatomical characters may be related to adaptability to the stressful conditions, as stem succulence, root aerenchyma, root starch reserves and epidermal cell of the stems with thick outer periclinal walls, however there was little convergence between species. Aerenchyma and water reserve tissue were the most frequent anatomical traits. In contrast, elevated cortex lignification in roots was the lowest occurrence trait, being a specific feature of the monocot.