Structural diversity of fruits: conceptual reflexions and taxonomic implications / Diversidade estrutural de frutos: reflexões conceituais e implicações taxonômicas

Abstract

Fruit either originates solely from the ovary or ovary and other floral parts and inflorescence. Besides the ovary itself, the pedicle, bracteoles, receptacle, hypanthium, sepals, petals and inflorescence axis are included in the fruit development. Analysis was made in embedded historesin/paraffin material and sectioned in microtome. In the fruit ontogeny the pericarp either may be non-multiplicative or multiplicative. In the first case, the ovary wall differentiates in pericarp without the installation of meristem. Adaxial, middle or abaxial meristems can be installed in the multiplicative pericarp fruits from the periclinal cell divisions that occur in both the epidermis and the ovary mesophyll. Separation tissue takes place in the carpel margins and midrib in dehiscent fruits or it can remain as residual tissue in indehiscent fruits. Fruit classification is complex, and it may show divergence in nomenclature among fruit specialists. Structural fruit ontogeny can be a useful tool for its classification. Fruit structure has been used as diagnostic character of species, genera and tribes of angiosperms. Hypothesis about fruit evolution indicates that apocarpic fruit with follicles can be a basic evolutionary condition, at least among the sensu lato dicots. The Araucaria angustifolia pine seed is considered here as a fruit with protocarps/spermatocarps.