Leaf anatomy as an aid to the taxonomy of the ‘babassu’ complex (Attalea species)

Abstract

• Seven Attalea species present in common uniseriate epidermis, expansion tissue with three cell layers and dorsiventral mesophyll. • Number of palisade parenchyma layers and the distinct leaf segment shapes on the margin and on the main vascular bundle are important diagnostic features in the group. • Attalea barreirensis, A. eichleri and A. vitrivir are grouped together in a Jaccard similarity analysis. The taxonomy of Attalea is still not mutually agreed upon by taxonomists. Since leaf anatomy is a useful tool to differentiate palm groups that are difficult to distinguish, this study aimed to check the taxonomic value of leaf anatomy of seven Attalea species, and estimate the genetic distance among the studied species. Samples were gathered in the Brazilian states of Maranhão, Tocantins, Bahia and Minas Gerais, and permanent slides were assembled following the classical plant anatomy protocol. All species presented uniseriate epidermis, glandular scars, tetracytic stomatal complex, expansion tissue with three cell layers and dorsiventral mesophyll. Attalea barreirensis was the only amphistomatic species, due to the constant fluctuation in soil moisture. The hypodermis was thinner in A. maripa , which is consistent with the humid habitats where the species occurs. In A. barreirensis and A. eichleri the distinction between palisade and spongy parenchyma was not so clearly seen, characterizing a gradual dorsiventral mesophyll. The distinct shapes of the margin and the main vascular bundle of the segments, as well as the number of palisade parenchyma layers, were important diagnostic features. The arrangement of vascular bundles and their connection with the hypodermis varied within the same species. Attalea barreirensis, A. eichleri and A. vitrivir had many anatomical features in common, which separated them from the remaining studied species. Leaf anatomy of the seven species was informative, and an anatomical identification key is provided.