Targeted manipulation of vine balance 2. A whole-vine chamber system for controlling berry sugar accumulation.

Vine balance, from a mechanistic perspective, can be considered as a source-sink relationship, i.e. the relationship between carbohydrate supply (via canopy photosynthesis) and the carbohydrate requirement of the developing fruit. Manipulating vine balance potentially affects the availability of carbohydrates to support berry development. However, when photosynthetic capacity is manipulated through canopy architecture or management practices, bunch exposure can also be affected. Identifying which factor has the greater influence on berry composition is therefore difficult under field conditions. To specifically manipulate whole vine carbohydrate availability, and in turn provide control over the rate of berry sugar accumulation, an experimental approach was developed to reduce photosynthesis by supplying whole vines with air at CO2 concentrations below ambient levels. This poster reports on the design and testing of this system,and the results of the first experiment which examined the impact of low post-verais on carbohydrate supply on berry sugar accumulation and composition.