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~ Grape Growing Information ~

Carbohydrate Transloction
by Carmo Vasconcelos
THE BASICS
  • Carbohydrates are translocated in the phloem
  • The main carbohydrate translocated throughout the grapevine is sucrose
  • Assimilates are translocated from the sites of production (leaves) or storage (organs) to the sinks


ENERGY COSTS OF
TRANSLOCATION
  • Loading and unloading the sucrose into the phloem: 14% of the amount translocated
  • The flow in the phloem is passive: no energy required
  • To maintain the phloem vessels in good shape: energy cost are proportional to the translocation distance
GRAPEVINE GROWTH CYCLE



BUD BREAK TO 4 LEAVES
There is only import from the reserves

5 LEAVES
The first leaf starts exporting carbohydrates

6 - 8 LEAVES

6 - 8 LEAVES
At this stage the new roots start to grow




10 leaves
The shoot becomes almost independent from the reserves

12 - 14 leaves
Bud for the next season start developing

BLOOM
The infloresence in not an important sink for the carbohydrates at this stage

BLOOM
Root growth reaches its maximum peak at bloom




Removing the shoot tip eliminates the competition between the growing vegetative and the infloresence, improving fruit set

FRUIT SET

Lateral shoots with two or more expanded leaves provide carbohydrates to their growing tip and export the surplus to the main shoot, contributing to fruit ripening

Leaves from lateral shoots bearing clusters suply the fruit on the lateral first and export the surplus to the main shoot




VERAISON
At this stage all leaves export to the fruit

RIPENING

AFTER HARVEST
All carbohydrates move downward. There is another flush of root growth
This presenatation was given by Ms Vasconcelos at the 2002 MGGA Annual Meeting and is reprinted here with her permission.



Maryland Grape Growers Association ©2017