Morfoanatomia do fruto e da semente em Passovia pedunculata (Jacq.) Kuijt: novos registros e contribuições em Loranthaceae Juss

Abstract

Loranthaceae is one of the main families of parasitic plants occurring in Brazil. The anatomical structure of the fruit and seeds, and their relationship with the establishment of the parasite-host relationship, is still little studied. Therefore, the present proposal aims to describe the morphoanatomy and histochemistry of the fruit and seed of the species Passovia pedunculata (Jacq.) Kuijt. The fruits of the studied species have a reddish epicarp when ripe and when sectioned, they expose a layer of viscine that surrounds the seed, a yellowish endosperm and in the center, a well-differentiated chlorophyll embryo. Anatomically, the mature fruit has a uniseriate epicarp, a mesocarp consisting of different layers, one underlying the epicarp, followed by a layer of viscine and two layers of cells that accumulate phenolic compounds. However, the endosperm does not form a very distinct layer and the fruit connects directly to the seed. The embryo positions the root axis close to the fruit rupture region. Histochemical tests were focused on viscine, demonstrating the presence of polysaccharides, proteins, lipids, mucilage, phenolic compounds and pectins. These results may be related to protective aspects of the seed, as well as the adhesive importance of the embryo to the host. The study clarifies for the first time the occurrence of endosperm, absent in other genera, but possibly common throughout the Passovia genus, in addition to proposing a model for recognizing the layers of the fruit. Therefore, the present study stands out as the first record for the genus Passovia and the first among the Loranthaceae of Brazilian flora.