Abstract
Grapevine (Vitis vinifera cv. Cortese) plants were grown in containers, and their single shoot was trained either upwards or it was bent to a horizontal or downward position. Clusters and lateral shoots were removed. Downward shoots had less leaf area and a lower stem diameter than did horizontal and upward shoots. In downward shoots, net photosynthesis and stomatal conductance, measured at maximum irradiance, were lower than in horizontal and upward shoots; these differences were more evident at the middle nodes of the shoot. The substomatal CO2 concentration was not affected by shoot orientation, suggesting a non-stomatal limitation of photosynthesis. This hypothesis was supported by a reduced protein content and a lower activity of ribulose 1,5-bisphosphate carboxylase/oxygenase in leaves of downward shoots. Downward shoots also had less xylem transectional area and a lower hydraulic conductance than did horizontal and upward shoots. Conductance was more reduced at the point of bending than at other internodes.
- Received May 1994.
- Copyright 1995 by the American Society for Enology and Viticulture
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