Method of opening the fruits, biometry and anatomical description of embryonic development in pau-branco (<i>Cordia oncocalyx</i> Allemão) seeds

Abstract

The tree species Pau-branco, Cordia oncocalyx Allemão has great economic potential, especially for logging, but its extraction is uncontrolled and can cause depredation. This type of harvest does not guarantee sufficient raw material to supply the demanding sectors such as furniture industries. The propagation of the species in plant nurseries starting from fruits and seeds could offer a solution to this problem. However, the fruits obtained from native plants comprise different sizes and different degrees of ripeness, making germination and propagation processes a difficult task. Knowledge of the final zygotic embryogenesis (fruit phase) anatomy is very important to establishing a propagation protocol for this species, especially to achieve a successful seed rescue of those containing mature zygotic embryos. The objectives of the present work was to establish a method to open the fruits and to study the microstructure and anatomy of the embryo in seeds of pau-branco, never shown before, with the goal of determining in which phase of development seed rescue is most appropriate for subsequent planting and seedling propagation. Mature fruits of pau-branco at different developmental stages were collected and subjected to microscopic investigation or biometrics determination. Transverse and longitudinal sections were obtained and processed for optical and scanning electron microscopy for the anatomical description of fruits and seeds. It was observed that the fruit has an exocarp and mesocarp. The mesocarp is divided into a sub exocarp-like mesocarp and a sclerenchymatous mesocarp, the latter of which gives hardness and rigidity to the fruit. The embryo, generally approximately 1.5 cm, is visible inside the fruits. When the embryo reaches 2.0 cm, it is considered fully developed, and it is recommend that excision can take place at this stage. the use of a hydraulic press was the most viable method for the extraction of seeds from the fruits. Furthermore, it was also concluded that the embryo of pau-branco seeds contain protein reserves.