Heavy bearing is a typical phenomenon on unshaded coffee (Coffea arabica L.) trees and limits both
the production and retention of leaves, leading to branch dieback, and, thus, results in a strong biennial
bearing pattern. The major goals of this study were to investigate the physiological mechanisms that may
be associated with the leaf-to-fruit ratio (LFR), branch dieback, biennial production and the relationships
betweencarbohydrate andmineralfluctuations and branchdieback incoffee plants. The trees were grown
in north–south-oriented hedgerows under conditions of full sunlight. Leaves and plagiotropic branches
from the upper and lower strata of the east- and west-facing sides of the hedgerow were examined.
A strong biennial pattern of coffee production was observed over three harvests. Overall, the east face
of the hedgerow produced a more sellable crop than the west face, and this was associated with more
light availability for the east-facing branches. The branch growth rate was higher with an increasing LFR
during 2006–2007, regardless ofthe canopyposition, andno compensatory increase inthephotosynthetic
rate was found in response to a decreasing LFR. Due to a relatively low fruit yield in 2007–2008, there
was no branch dieback. The extent of branch dieback increased dramatically with decreasing LFR and was
probably not closely related to changes in the concentrations of carbohydrates, amino acids and minerals.
The extent of branch dieback was apparently unrelated to the differences in the photosynthetic rates per
unit leaf area, carbon isotope composition, or oxidative stress, as was assessed by the electrolyte leakage
from the leaf tissues. We discuss these responses in terms of the relative lack of branch autonomy in
coffee trees.
Heavy bearing is a typical phenomenon on unshaded coffee (Coffea arabica L.) trees and limits both
the production and retention of leaves, leading to branch dieback, and, thus, results in a strong biennial
bearing pattern. The major goals of this study were to investigate the physiological mechanisms that may
be associated with the leaf-to-fruit ratio (LFR), branch dieback, biennial production and the relationships
betweencarbohydrate andmineralfluctuations and branchdieback incoffee plants. The trees were grown
in north–south-oriented hedgerows under conditions of full sunlight. Leaves and plagiotropic branches
from the upper and lower strata of the east- and west-facing sides of the hedgerow were examined.
A strong biennial pattern of coffee production was observed over three harvests. Overall, the east face
of the hedgerow produced a more sellable crop than the west face, and this was associated with more
light availability for the east-facing branches. The branch growth rate was higher with an increasing LFR
during 2006–2007, regardless ofthe canopyposition, andno compensatory increase inthephotosynthetic
rate was found in response to a decreasing LFR. Due to a relatively low fruit yield in 2007–2008, there
was no branch dieback. The extent of branch dieback increased dramatically with decreasing LFR and was
probably not closely related to changes in the concentrations of carbohydrates, amino acids and minerals.
The extent of branch dieback was apparently unrelated to the differences in the photosynthetic rates per
unit leaf area, carbon isotope composition, or oxidative stress, as was assessed by the electrolyte leakage
from the leaf tissues. We discuss these responses in terms of the relative lack of branch autonomy in
coffee trees.
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