Osmolality and non-structural carbohydrate composition in the secondary phloem of trees across a latitudinal gradient in Europe

• Published in: Frontiers in Plant Science
• Main Authors: Lintunen, Anna, Paljakka, Teemu, Jyske, Tuula, Peltoniemi, Mikko, Sterck, Frank, von Arx, Georg, Cochard, Hervé, Copini, Paul, Caldeira, Maria C., Delzon, Sylvain, Gebauer, Roman, Grönlund, Leila, Kiorapostolou, Natasa, Lechthaler, Silvia, Lobo-Do-Vale, Raquel, Peters, Richard L., Petit, Giai, Prendin, Angela L., Salmon, Yann, Steppe, Kathy, Urban, Josef, Roig Juan, Sílvia, Robert, Elisabeth M. R., Holtta, Teemu
• Other Authors: Department of Forest Sciences, University of Alaska Fairbanks (UAF), Natural Resources Institute Finland (LUKE), Wageningen University and Research Centre (WUR), Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Laboratoire de Physique et Physiologie Intégratives de l'Arbre Fruitier et Forestier (PIAF), Institut National de la Recherche Agronomique (INRA)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP), Alterra, Wageningen University and Research Wageningen (WUR), Forest Research Centre, School of Agriculture, Universidade de Lisboa (ULISBOA), Biodiversité, Gènes & Communautés (BioGeCo), Institut National de la Recherche Agronomique (INRA)-Université de Bordeaux (UB), Mendel University in Brno (MENDELU), Universita di Padova, Department of Physics, Laboratory of Plant Ecology, Department of Applied Ecology and Environmental Biology, Universiteit Gent = Ghent University Belgium (UGENT), Centre for Ecological Research and Forestry Applications (CREAF), Laboratory of Plant Biology and Nature Management (APNA), Vrije Universiteit Brussel (VUB), Laboratory of Wood Biology and Xylarium, Royal Museum for Central Africa Tervuren (RMCA)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2016
• Subjects: hexose; osmotic concentration; phloem water content; pinitol; sucrose; starch; raffinose; [SDV]Life Sciences [q-bio]; [SDE]Environmental Sciences; Northern Finland
• Online Access: https://hal.inrae.fr/hal-02635301; https://hal.inrae.fr/hal-02635301/document; https://hal.inrae.fr/hal-02635301/file/fpls-07-00726_1.pdf; https://doi.org/10.3389/fpls.2016.00726

International audience Phloem osmolality and its components are involved in basic cell metabolism, cell growth, and in various physiological processes including the ability of living cells to withstand drought and frost. Osmolality and sugar composition responses to environmental stresses have been extensively studied for leaves, but less for the secondary phloem of plant stems and branches. Leaf osmotic concentration and the share of pinitol and raffinose among soluble sugars increase with increasing drought or cold stress, and osmotic concentration is adjusted with osmoregulation. We hypothesize that similar responses occur in the secondary phloem of branches. We collected living bark samples from branches of adult Pinus sylvestris, Picea abies, Betula pendula and Populus tremula trees across Europe, from boreal Northern Finland to Mediterranean Portugal. In all studied species, the observed variation in phloem osmolality was mainly driven by variation in phloem water content, while tissue solute content was rather constant across regions. Osmoregulation, in which osmolality is controlled by variable tissue solute content, was stronger for Betula and Populus in comparison to the evergreen conifers. Osmolality was lowest in mid-latitude region, and from there increased by 37% toward northern Europe and 38% toward southern Europe due to low phloem water content in these regions. The ratio of raffinose to all soluble sugars was negligible at mid-latitudes and increased toward north and south, reflecting its role in cold and drought tolerance. For pinitol, another sugar known for contributing to stress tolerance, no such latitudinal pattern was observed. The proportion of sucrose was remarkably low and that of hexoses (i.e., glucose and fructose) high at mid-latitudes. The ratio of starch to all non-structural carbohydrates increased toward the northern latitudes in agreement with the build-up of osmotically inactive C reservoir that can be converted into soluble sugars during winter acclimation in these cold ...