Source-sink balance in grapevine as affected by training system

Vegetative growth, productivity and the physiological behaviour of Sangiovese grapevines in a Tuscan vineyard were evaluated as affected by two trellis systems: single cordon and a low double cordon (Lyre trellis). The vines were spurpruned and cordon trained and shoots vertically positioned. The planting density was 6667 vines ha-1. The research was carried out in 2002. The two trellising systems were distributed in a randomized block design with 4 replications of 3 rows each. Data were collected from the central row. Light interception, photosynthesis efficiency as well as vegetative and reproductive characteristics were measured. Light interception readings were collected 10 cm above the ground at every 10 cm of row width. Leaf gas exchange measurements were performed with a CIRAS 1 gas analyzer. Light interception was greater for the Lyre system compared to the single cordon, especially mid-morning, when the sun elevation was higher. No differences in single leaf photosynthesis measurements were found between the trellis systems indicating whole plant photosynthesis of the Lyre was greater. Vegetative growth was also higher for the Lyre. The Lyre trellis had greater yield due to both greater cluster number and cluster weight compared to the single curtain. No differences in must sugar content or anthocyanins were observed. In conclusion, the greater light intercepting leaf area of the Lyre trellis can support a higher yield without affecting quality. This is probably due to greater whole canopy photosynthesis of the Lyre compared to the single curtain.