Biology and structure of flowers in Adenium obesum (Forssk.) Roem. & Schult. (Apocynaceae) accessions with notes on the significance of these features for floriculture

Adenium obesum (Forssk.) Roem. & Schult. is an important plant for the floriculture sector. Detailed information on floral structures is scarce and important for breeding programs, especially considering the great phenotypic variability. The objective of this study was to describe the floral events, morphology and anatomy of three A. obesum (Forssk.) Roem. & Schult. accessions (ICA-rt, ICA-wd and ICA-ps) relating these traits to the ornamental value and to species propagation. The accessions bloomed throughout most of the evaluation period, and their flowers opened during the morning. The time elapsed from initiation until the opening of the bud ( ≈ 32 days), as well as the floral longevity ( ≈ 27 days), was longest for ICA-rt accession. The morphological and anatomical analysis detected phenotypic diversity in A. obesum (Forssk.) Roem. & Schult. Variations in the reproductive organs, levels and types of male sterility, as well as a reduced female fertility, were reported. Hercogamy and functional dioecy were registered. The high floricultural potential of ICA-rt accession was identified, in view of its morphological, morphometric and floral longevity features. These results may inspire several new studies on A. obesum (Forssk.) Roem. & Schult. in the fields of applied genetics and plant breeding.