Articles
THE GRAPE BERRY AS A SINK
Article number
239_20
Pages
149 – 158
Language
Abstract
The ripening grape berry is a strong sink for dry matter transported into it from current photosynthesis or reserves in wood.
The inception of accumulation is coincident with the onset of berry softening.
Most accumulation is as solutes into the water of the berry which is itself also accumulating.
The rate of solute increase relates to a rate of water accumulation that gives a steady rise in concentration.
While sink size is the major determinant of total sink strength, sink activity is the important factor during the first week of accumulation when berry expansion is slow.
The inception of accumulation is coincident with the onset of berry softening.
Most accumulation is as solutes into the water of the berry which is itself also accumulating.
The rate of solute increase relates to a rate of water accumulation that gives a steady rise in concentration.
While sink size is the major determinant of total sink strength, sink activity is the important factor during the first week of accumulation when berry expansion is slow.
Berry skin, when excised and incubated in a glucose-containing medium, metabolizes the glucose via sucrose and compartments fructose, glucose and malate by an active transport process.
Curiously, this active process is found to occur in excised skin from both green (non-accumulating) and ripening skin, but not in excised flesh.
This suggests a control further back in the transport pathway; the evidence indicates phloem unloading.
The triggering of accumulation appears not to be due to activation of apoplastic invertase, but may be connected to endogenous activity of abscisic acid.
Authors
B.G. Coombe
Keywords
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