© 2004 Heron Publishing—Victoria, Canada
Trophic control of bud break in peach (Prunus persica) trees: a possible role of hexoses
Karine Maurel (1, 2), Gabriel Berenhauser Leite (2, 3, 4), Marc Bonhomme (3), Agnès Guilliot (1), Rémy Rageau (3), Gilles Pétel (1) and Soulaïman Sakr (1, 5)
1. UMR 547-PIAF, Université Blaise Pascal, 24 avenue des Landais, 63177 Aubière Cedex, France / 2. These authors contributed equally to the paper / 3. UMR 547-PIAF INRA, domaine de Crouël, 234 avenue du Brézet, 63039 Clermont-Ferrand Cedex 2, France / 4. EPAGRI/UnC/CAPES, CP 591, 89500-000 Caçador, SC, Brazil / 5. Corresponding author (soulaiman.sakr@piaf.univ-bpclermont.fr) / Received July 25, 2003; accepted October 19, 2003; published online March 1, 2004
Summary
Vegetative buds of peach (Prunus persica L. Batsch.) trees act as strong sinks and their bud break capacity can be profoundly affected by carbohydrate availability
during the rest period (November–February). Analysis of xylem sap revealed seasonal changes in concentrations of sorbitol
and hexoses (glucose and fructose). Sorbitol concentrations decreased and hexose concentrations increased with increasing
bud break capacity. Sucrose concentration in xylem sap increased significantly but remained low. To clarify their respective
roles in the early events of bud break, carbohydrate concentrations and uptake rates, and activities of NAD-dependent sorbitol
dehydrogenase (SDH), sorbitol oxidase (SOX) and cell wall invertase (CWI) were determined in meristematic tissues, cushion
tissues and stem segments. Only CWI activity increased in meristematic tissues shortly before bud break. In buds displaying
high bud break capacity (during January and February), concentrations of sorbitol and sucrose in meristematic tissues were
almost unchanged, paralleling their low rates of uptake and utilization by meristematic tissues, and indicating that sorbitol
and sucrose play a negligible role in the bud break process. Hexose concentrations in meristematic tissues and glucose imported
by meristematic tissues correlated positively with bud break capacity, suggesting that hexoses are involved in the early events
of bud break. These findings were confirmed by data for buds that were unable to break because they had been collected from
trees deprived of cold. We therefore conclude that hexoses are of greater importance than sorbitol or sucrose in the early
events of bud break in peach trees.
Keywords:
carbohydrate metabolism, meristematic tissues, sorbitol, vegetative bud, xylem sap.
