The effects of cane girdling before budbreak on shoot growth, leaf area and carbohydrate content of Vitis vinifera L. Sauvignon Blanc grapevines

The influence of restricting available carbohydrates (CHOs) on shoot growth was studied by cane girdling field grown Vitis vinifera L. Sauvignon Blanc grapevines before budbreak. Canes were girdled 5, 10 or 20cm from the terminal bud of the cane, and the shoot growth of the terminal bud was monitored over the course of a single growing season. A linear relationship was found between the initial rate of shoot growth and the amount of cane isolated by the girdle. A decrease in available CHOs during initial shoot growth appeared to inhibit the shoot's ability to produce new vegetative nodes past the point of discontinuity, resulting in a decrease in total leaf area due to incomplete leaf expansion. The transition from the vine's dependence on reserve CHOs to a net positive state appeared to occur when shoot growth reached a steady state. In the case of severe CHO restriction, no lateral growth occurred, suggesting the CHO status in the vine may play a role in lateral bud growth. The cross-sectional area of canes or shoots were shown to have a linear relationship to their CHO content, which allows for an estimation of the amount of CHOs required to obtain growth similar to the control treatment. Additionally, main shoot leaf area can be used to predict total CHO content in the shoot at harvest.