Non-structural carbohydrates stored in belowground organs point to the diversity in Amaranthaceae

Abstract

Amaranthaceae is a cosmopolitan and diverse family, with characteristics that enable plants to occupy habitats with harsh environmental conditions. The Brazilian Cerrado has numerous features that impose challenges to plant survival, such as seasonal drought and fires. Nearly one hundred species of Amaranthaceae occur in the Cerrado and many of them have thickened belowground systems that store non-structural carbohydrates. In this study, we analyze patterns in the adaptive strategies of Amaranthaceae species that occur in the Cerrado, by assessing the types of carbohydrates stored in the belowground systems and biomass allocation in light of photosynthetic characteristics reported in the literature. We analyzed species of Amaranthus (C4), Alternanthera (C3-C4), Froelichia (C4), Gomphrena (C4), and Pfaffia (C3). All the analyzed species had non-structural carbohydrate content higher than 20% of the dry mass. Sucrose was the main non-structural carbohydrate found in the belowground organs of Alternanthera tenella and Amaranthus viridis. Starch was detected only in Amaranthus viridis. All other species accumulate fructans; Pfaffia spp. have inulin-type fructans while Gomphrena and Froelichia have levan-type fructans. Two morphophysiological syndromes are characterized by the lowest or highest investment in belowground system mass and storage of fructans, being interpreted as generalist or specialist adaptive strategies. These two characteristics of such syndromes, together with the photosynthetic metabolisms are traits that reflect the diversity of the Amaranthaceae and their ability to occupy several habitats, including those marked by harsh conditions, such as the Cerrado.