Seasonal growth and gas exchange of conventionally and minimally pruned Chardonnay canopies

The net CO2 gas exchange rate (NCER) of hand-(HP) and minimally pruned (MP) potted Chardonnay canopies was continuously monitored from about 20 d after budburst until post-harvest. Single-leaf gas exchange readings were taken 4 times throughout the season and non-destructive estimates of leaf chlorophyll at veraison. Canopy leaf area development was registered, yield components and grape soluble solids were recorded at harvest; samples were taken to determine dry matter partitioning into clusters, leaves and canes. The MP vines showed higher shoot number, distinctly reduced leaf and shoot size, and a higher cluster number with smaller berries and less berries per cluster compared to HP vines. The MP vines exhibited a 4-6-fold higher CO2 fixation than HP vines from about three weeks after budbreak till bloom. Canopy NCER started to recover in HP vines concurrently with the transition to a faster shoot growth phase, although by canopy completion NCER was still 13 % higher in MP. Sugar concentration of berries was not significantly lower in MP compared to HP despite a yield increase of about 70 %. The overall results indicate minimal pruning as a valuable tool to improve the performance of Chardonnay vines under our experimental conditions.