Characterisation of fructan accumulation in grasses and its implication for cold adaptation and overwintering

Abstract

Fructans are fructose-based oligo- and polysaccharides that occur in many plants in temperate climates. Beside its main function as storage carbohydrate, fructan has been suggested to play a role in temperate adaptations, e.g., as cryoprotectant or by increasing photosynthesis efficiency at low temperatures. Here, I investigate the role of fructans in winter survival and global distribution of perennial temperate grasses by conducting a common garden experiment with 35 phylogenetically diverse species. Sampling of crown material was performed once a month from 30th October 2019 to 29th April 2020 and fructan content in the samples was analysed and quantified with high performance anion exchange chromatography coupled with pulsed amperometric detection. The results were combined with a phylogenetic tree to investigate the correlation of fructan accumulation with regrowth in spring as well as global distribution data. I identified several new fructan accumulators in the Pooideae subfamily and my results reveal a large variety in fructan types among Pooideae species. The observed phylogenetic pattern of fructan types suggests several independent origins of FTs and FEHs in the subfamily. Furthermore, fructan amount throughout the winter showed a clear correlation with regrowth ability in spring, a measure of frost tolerance and winter endurance. A reciprocal relationship was found between the bioclimatic variable isothermality and amount of fructan throughout the winter months. A phylogenetic analysis of variance with global distribution data revealed a striking pattern of fructan accumulators being able to survive in areas with longer winters than non-fructan accumulators.