ISHS Acta Horticulturae 662: VII International Symposium on Temperate Zone Fruits in the Tropics and Subtropics
INFLUENCE OF LACK OF CHILLING ON BUD-BREAK PATTERNS AND EVOLUTION OF SUGAR CONTENTS IN BUDS AND STEM TISSUES ALONG THE ONE-YEAR-OLD SHOOT OF THE PEACH TREES |
| Authors: | G.B. Leite, M. Bonhomme, A. Lacointe, R. Rageau, S. Sakr, A. Guilliot, K. Maurel, G. Petel, A. Couto-Rodriguez |
| Keywords: | Prunus persica, dormancy, carbohydrate gradients, bud position, leaf bud, floral bud |
| Abstract:
Through experiments providing different amounts of chilling to trees before they were given forcing temperatures, the influence of this amount on the budbreak pattern of peach tree was investigated with special regards to the dynamics of development of the buds according to their place along the twig. Vegetative and floral budbreak was recorded on the trees. Leaf bud endodormancy was characterized by the mean time of bud break (MTB) through the ‘cuttings’ test. Dry weight of floral primordia was measured. On the basis of the hypothesized ‘trophic’ control of the primordia growth and development, sucrose, sorbitol, fructose and glucose contents were assayed in the buds and stem. Under natural conditions (NC) and under total chilling deprivation (TCD) the results on bud development (MTB, growth of floral primordia) and budbreak (good budbreak under NC, no budbreak under TCD) confirmed former results on peach (especially, under both treatments no gradients along the twig). Under NC, in floral buds, the sugar contents showed at the budbreak time starch and hexose increases and a decrease of sucrose and sorbitol. In leaf buds, only the starch showed an increase. Sucrose, sorbitol and hexoses stayed stable. Under TCD, all carbohydrates stayed stable. Under the treatment ‘chilling amount = 1/3 requirements’ (PCD1), a few buds broke. The rates of leaf and floral budbreaking (consistently with MTB data) and floral bud drop showed longitudinal gradients. The dynamics of sugar specific contents showed a transitory oscillation, in opposite way in leaf and floral buds, and with stronger amplitude at the basal part of the stem. In floral buds, the sugar contents at the budbreak time stayed stable to starch and hexose, decreased for sorbitol and increase for hexoses. In leaf buds, all carbohydrates stayed stable. Under the treatment ‘chilling amount = 2/3 requirements’ (PCD2), most leaf and many floral buds broke, but many flowers dropped at bloom. Slight acrotonic gradients could be observed. For most of the sugars and tissues the dynamics of sugar specific contents looked like those under NC; however, they showed gradients (for instance, an early hexoses gradient consistent with the acrotonic floral buds bloom). In floral buds, the sugar contents showed at the budbreak time a starch and sucrose stability, a decrease of sorbitol and an increase of hexoses. In leaf buds, only the starch increased. Sucrose, sorbitol and hexoses stayed stable. The availability of carbohydrates would not be the key factor of the pattern of budbreak. The capacity to use soluble sugars seems to be more critical. The capacity to synthesize starch could be a marker for growth capacity. | |
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