Morphological Characterization, Pollen Viability, and Germinability Evaluation of Two Plumeria Species in the University of the Philippines Los Baños

The genus Plumeria, locally known as kalachuci, is a popular ornamental tree belonging to the Apocynaceae family. The University of the Philippines Los Baños (UPLB) maintains a collection of Plumeria trees scattered across its campus; however, the origin of these trees remains unclear due to a lack of proper documentation. This study conducted morphological characterization and pollen analysis to provide information for further research. Results revealed the presence of 2 Plumeria species in the campus. P. obtusa has a linear leaf shape with acute tips and revolute margins while P. rubra has a lanceolate leaf shape. Additionally, P. obtusa has a green peduncle while P. rubra has a peduncle ranging from red to dark red. In terms of floral traits, P. obtusa produces white flowers while P. rubra has flowers with a variety of colors including white, yellow, pink, and dark red. Pollen viability and pollen germinability analysis revealed that germinability varied significantly within and between species, whereas pollen viability remained similar for both. Both species exhibited high pollen viability observed through staining but low pollen germination. Furthermore, high pollen viability does not guarantee high germinability, as indicated by the weak correlation between these variables across species. To clarify the uncertain provenance of P. rubra variants, further research using molecular techniques and DNA markers for precise information is highly recommended.