Carbohydrate reserves as a competing sink : evidence from tapping rubber trees

Silpi Unakorn, Lacointe André, Kasempsap P., Thanysawanyangkura S., Chantuma Pisamai, Gohet Eric, Musigamart Natedao, Clément Anne, Améglio Thierry, Thaler Philippe. 2007. Carbohydrate reserves as a competing sink : evidence from tapping rubber trees. Tree Physiology, 27 (6) : 881-889.

Résumé : Carbohydrate reserve storage in trees is usually considered a passive function, essentially buffering temporary discrepancies between carbon availability and demand in the annual cycle. Recently, however, the concept has emerged that storage might be a process that competes with other active sinks for assimilate. We tested the validity of this concept in Hevea brasiliensis Müll. Arg. (rubber) trees, a species in which carbon availability can be manipulated by tapping, which induces latex regeneration, a high carbon-cost activity. The annual dynamics of carbohydrate reserves were followed during three situations of decreasing carbon availability: control (no tapping), tapped and tapped with Ethephon stimulation. In untapped control trees, starch and sucrose were the main carbohydrate compounds. Total nonstructural carbohydrates (TNC), particularly starch, were depleted following bud break and re-foliation, resulting in an acropetal gradient of decreasing starch concentration in the stem wood. During the vegetative season, TNC concentration increased. At the end of the vegetative season, there were almost no differences in TNC concentration along the trunk. In tapped trees, the vertical gradient of starch concentration was locally disturbed by the presence of the tapping cut. However, the main effect of tapping was a dramatic increase in TNC concentration, particularly starch, throughout the trunk and in the root. The difference in TNC concentration between tapped and untapped trees was highest when latex production was highest (October); the difference was noticeable even in areas of the trees that are unlikely to be directly involved in latex regeneration, and it was enhanced by Ethephon stimulation, which is known to increase latex metabolism and flow duration. Thus, contrary to what could be expected if reserves serve as a passive buffer, a decrease in carbohydrate availability resulted in a net increase in carbohydrate reserves at the trunk scale. Such behavior supports the view that trees tend to adjust the amount of carbohydrate reserves stored to the level of metabolic demand, at the possible expense of growth.

Mots-clés Agrovoc : Hevea brasiliensis, rendement des cultures, amidon, glucide, stockage, développement biologique, croissance, compétition biologique, variation saisonnière, organe de réserve

Mots-clés complémentaires : Sink effect

Classification Agris : F62 - Physiologie végétale - Croissance et développement

Champ stratégique Cirad : Axe 1 (2005-2013) - Intensification écologique

Auteurs et affiliations

• Silpi Unakorn, Kasetsart University (THA)
• Lacointe André, INRA (FRA)
• Kasempsap P., Kasetsart University (THA)
• Thanysawanyangkura S., Kasetsart University (THA)
• Chantuma Pisamai, RRIT (THA)
• Gohet Eric, CIRAD-CP-UPR Systèmes de pérennes (FRA) ORCID: 0000-0002-0379-0592
• Musigamart Natedao, Kasetsart University (THA)
• Clément Anne, CIRAD-AMIS-UPR Modélisation intégrative (FRA)
• Améglio Thierry, INRA (FRA)
• Thaler Philippe, CIRAD-FORET-UPR Ecosystèmes de plantations (THA) ORCID: 0000-0002-9924-4309

Source : Cirad - Agritrop (https://agritrop.cirad.fr/537197/)

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