ISHS Acta Horticulturae 395: Dormancy and the related Problems of Deciduous Fruit Trees
RESPIRATORY CHANGES DURING DORMANCY BREAKING OF APPLE TREES |
| Authors: | E. Young, T.K. Dautlick, R.D. Belding |
| Keywords: | Malus domestica (Borkh.), Endodormancy, Ecodormancy, Chilling requirement |
| Abstract:
During endodormancy and accumulation of their chilling requirement (CR), apple trees carry on metabolic functions through maintenance respiration. As trees enter ecodormancy and begin accumulating heat units, the respiration level usually increases significantly. Various studies at NCSU have demonstrated a number of conditions and responses related to this change in respiration as apple trees progress toward budbreak. Trees require 80% of their CR before respiration will increase with higher temperatures during ecodormancy. The Q10 for respiration increases from 1.5 to 2.5 as trees complete their CR. During the same period, respiratory energy of activation decreases from 18 to 12 kcal/mole. As trees are chilled up to 80% of their CR, respiration becomes less sensitive to ambient O2 concentration, and the respiratory quotient increases from 0.25 to 1.0. After the CR is satisfied, respiration level of single internodes during ecodormancy decreases with distance from the tree's apex. Over-chilling beyond the CR will diminish this gradient. | |
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