Effects of modifying root temperature in field grown 'Cabernet Sauvignon' on carbohydrate reserve dynamics and vine development

The carbohydrate reserve pool of the perennial structure of grapevines is determined by internal requirements for growth and the production of assimilates. In addition, the processes of depletion and replenishment of reserves during the growing season are altered by the vineyard environment and by viticultural practices. The mobilisation and storage of reserves can also be influenced by the soil environment, with warmer root temperatures in spring increasing the mobilisation of root reserves and the shoot biomass. This study was conducted on mature, field-grown grapevines V. vinifera L. 'Cabernet Sauvignon' over two growing seasons, to examine the carbohydrate reserve dynamics and growth responses to soil temperature as modified by plastic sheet and straw mulches. The surface treatments significantly influenced root zone temperature to a depth of 30 cm or more, with the temperatures under the plastic sheet being up to 10°C higher than under the plastic/straw treatment. The carbohydrate root reserve concentrations declined from bud-break to flowering by more than half, with the increases in soil temperature considerably elevating the mobilisation of the root reserves. The implemented soil temperature regimes had a minor influence on canopy growth and reproductive development, although berry maturation was enhanced by warmer soil temperatures. These findings indicate a change of source-sink relationships through altered soil temperatures, with consequences for root processes and above ground development. This suggests that soil management practises that alter root temperature can contribute, not only to reserve dynamics, but also influence berry maturation and composition.