Morphoanatomy of dry fruits in Apocynaceae species: ecological and evolutionary significance

Dry fruits predominate in Apocynaceae species, especially the follicle type reported for Aspidosperma parvifolium A.DC., Mesechites mansoana (A.DC.) Woodson and Prestonia coalita (Vell.) Woodson. Anatomical analysis of intact and open fruits was carried out to compare characteristics with those of other species of this family. We found that the fruit of P. coalita is a bicarpellary septicidal capsule, showing that this genus has two types of fruits instead of one as previously thought. Capsules may be found in other Prestonia species and in other Apocynaceae genera reported as having follicles. For Apocynaceae, some taxonomic characters should be considered such as thickness and number of pericarp layers and sublayers; presence of aerenchyma, sclereids, non-lignified fibres, secretory idioblasts in the mesocarp; vascular-bundle position in the mesocarp; endocarp thickness and fibre orientation; presence of internal ribs in the pericarp. Furthermore, the role of the internal ribs of the pericarp, as well as the non-lignified mesocarp fibres for the xerocastic mechanism are discussed. A total dehydration test was developed to determine maximum pericarp curvature and its implications for the dehiscence process.

dehiscence; follicle; capsule; evolution; Cerrado