Plant anatomy; volatile compounds; secretory spaces; Fabales; croceus glands; Polygaleae; Taxonomy.

Senega Spach is the most representative subgenus of Senega, and its sister groups are Clinclinia (DC.) J.

F. B. Pastore & Agust. Martinez and Monninopsis (S. F. Blake) J. F. B. Pastore & J. R. Abbott, with about 194 species is subdivided into 16 sections: Cleistogamae J. F. B. Pastore & J. R. Abbott, Cruciatae J. F. B. Pastore & J. R. Abbott, Cuspidatae J. F. B. Pastore, Decurrentes (Chodat) J. F. B. Pastore & J. R. Abbott, Densifoliarum (Marques) J. F. B. Pastore, Exiguae J. F. B. Pastore, Galioideae (Chodat) J. F. B. Pastore, Incarnatae (Chodat) J. F. B. Pastore & J. R. Abbott, Nudicaules (Chodat) J. F. B. Pastore, Revolutae J. F. B. Pastore, Sanguineae J. F. B. Pastore & J. R. Abbott, Senega DC., Tenues (Chodat) J. F. B. Pastore, Timutua DC., Trichospermae (Chodat) J. F. B. Pastore & J. R. Abbott and Verticillatae J. F. B. Pastore & J. R. Abbott. The subgenus consists of species characterized by the presence of croceous glands, which are solely classified according to their occurrence in vegetative and reproductive organs, without a real understanding of their functionality for plants. In this context, anatomical studies with complete micromorphological analyses and a significant sample number can produce new taxonomic and evolutionary interpretations about the glands. The present study aimed to inventory the glands existing in the stem, leaf, floral parts and fruit of representatives of Senega subgenus Senega, to know their taxonomic applicability and understand aspects about their origin, anatomical structure, function and chemical nature. In the first chapter, leaves of 72 species were sampled, representing all sections of the subgenus Senega and related groups, subgenus Clinclinia, subgenus Monninopsis, the genus Hualania Phil. and Muraltia DC. From the anatomical analyses, the glands were defined as cavities, coalescent cavities and secretory ducts, present in the sections Cruciatae, Cuspidatae, Decurrentes, Densifoliarum, Galioideae, Nudicaules, Sanguineae, Tenues, Timutua, Trichospermae and Verticillatae. For the sections Exiguae, Incarnatae, Senega and outgroups, no glands were observed. The glands were classified according to their occurrence, typology, position in the mesophyll, developmental stage and number of epithelial layers. In the second chapter, the glands existing in the ovary and fruit of Senega longicaulis were investigated regarding the origin, structure, composition and potential function of their secretion. The results revealed that the croceous glands are secretory spaces that produce volatile terpenes with a protective function in Senega. Structurally, these glands are cavities and the divergence in their typology, compared to other species of the genus, suggests the presence of transitional structures between cavities and ducts. In the third chapter, the volatile compounds existing in Senega adenophora, Senega apppressa and Senega longicaulis were analyzed in order to characterize the chemical profile of the aroma and essential oil. In the aroma, the predominant metabolic classes for S. adenophora were hydrocarbon sesquiterpenes, for S. appressa they were hydrocarbon sesquiterpenes and benzenoids, for S. longicaulis they were benzenoids and oxygenated sesquiterpenes. For the essential oil, oxygenated sesquiterpenes characterized the chemical profile of S. longicaulis. This study significantly expanded the knowledge about the anatomical structure, ontogeny, and chemical composition of the croceous glands in Polygalaceae.