Diversity of non-structural carbohydrates in the underground organs of five Iridaceae species from the Cerrado (Brazil)

Abstract

South America has a great diversity in some tribes of the Iridaceae family. Most of the Iridaceae are geophytes, with underground organs bearing buds and reserve compounds, which favor their occurrence in seasonal environments, such as the Cerrado. Non-structural carbohydrates (NSC) are the main reserves in geophytes, essential to support phenological events, and protect plants against abiotic stresses. NSC may also reflect taxonomic relationships among plant groups. The objective of this study was to determine the contents and composition of NSC in underground organs of five Iridaceae species from the Cerrado (Cipura paludosa, Cipura xanthomelas, Trimezia cathartica, Trimezia juncifolia and Sisyrinchium vaginatum), representing the tribes Tigridieae, Trimezieae and Sisyrinchieae. Soluble carbohydrates and total fructose in oligo and polysaccharide fractions, and the starch contents were determined, and sugar composition was analyzed by HPAEC-PAD. The species from the tribes Trimezieae and Tigridieae showed similar NSC profiles, with considerable accumulation of starch and glucose, fructose, sucrose and maltose. Additionally, T. juncifolia also presented raffinose and 1-kestose. In contrast, S. vaginatum of the Sisyrinchieae has very low starch content and a distinct carbohydrate profile, predominating soluble carbohydrates, possibly of the raffinose family.