Influences of cold deprivation during dormancy on carbohydrate contents of vegetative and floral primordia and nearby structures of peach buds (Prunus persica L. Batch)

Endogenous carbohydrate contents and availability in structures near the meristematic zone (scales, cushion, part of stem) during winter with and without sufficient chilling were investigated. Insufficient chilling is known to provoke an abnormal pattern of budbreak and development in temperate zone fruit trees cultivated in warm climates. Mild temperatures applied during winter to strictly floral buds, as is the case in peach, are known to provoke the necrosis of flower primordia in the buds. One of the hypotheses to explain this is that carbohydrate fluxes to the buds are impeded and/or that internal reserves are completely used up. Carbohydrate availability and bud survival were compared between peach trees under natural temperate conditions and under complete deprivation of cold, by keeping trees in a greenhouse with temperature constantly above 15 °C from early October to the first sign of necrosis in flower buds. Concentrations and carbohydrate contents were compared during a little more than 2 months (beginning mid-December) before the first signs of necrosis in flower buds. Results showed that cold deprivation deeply disturbed carbohydrate dynamics, blocking the import of carbohydrates into vegetative and floral primordia, even though sucrose and sorbitol concentrations within these structures remained high. Conversely, soluble carbohydrates accumulated strongly in bud scales and in the cushion beneath the primordia. This suggests a strong diversion towards structures close to the primordia under cold deprivation. However, since sucrose and sorbitol concentrations in the floral primordia remained high, necrosis could be the consequence of the inability to use sucrose and sorbitol reserves rather than the result of a lack of available carbohydrates.