Resumo

CASIERRA-POSADA, Fánor; SEPULVEDA, Carlos A.  e  AGUILAR-AVENDANO, Óscar E.. BUDBREAK OF APPLE TREES (Malus domestica BORKH. CV. ‘ANNA’) IN RESPONSE TO DEFOLIATION TIMING. rev.udcaactual.divulg.cient. [online]. 2008, vol.11, n.1, pp.113-122. ISSN 0123-4226.

SUMMARY Although culture requirements have been established for ‘Anna’ apple trees grown in the tropical highlands, little is known about the physiological and biochemical events that mark the end of chilling requirements and the beginning of budbreak. Under tropical conditions in Colombia, floral buds of apple burst at any time of the year in response to removal of the leaves after harvest, to pruning and to spraying of chemical inducers. The present work was carried out to evaluate the response of apple trees cv. ‘Anna’ to defoliation timing before or after harvest time in Paipa, Colombia. Different trees were defoliated one week before, at harvest and one to four weeks after harvest. Control plants were not defoliated and leaves remained on twigs during the experiment time up to their natural fall. As response variables, nitrogen, carbon contents and the C/N ratio in the floral buds at defoliation and at budbreak were measured; dry weight of the floral buds was also determined at defoliation and at budbreak, as well as the days from defoliation to burst. As results, the leaf removal reduced the time from defoliation to budbreak. The defoliation timing affected positively the burst percentage and the dry weight of floral buds, while nitrogen and carbon contents in buds remained unchanged. While control plants without leaf removal showed 32.6% budbreak, this was 94.6% for the trees defoliated one week after harvest, showing the beneficial effect of the defoliation on the budbreak.

Palavras-chave : C/N ratio; nitrogen; carbon; dry weight.

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