Water relations and vulnerability to embolism are not related: Experiments with eight grapevine cultivars

Abstract

Drought tolerance mechanisms at the leaf level have been reported for grapevines but less is known about their vulnerability to embolism caused by water stress. The objective of this experiment was to determine if there is a relationship between xylem hydraulic characteristics and drought resistance mechanisms at the leaf level. The experiment was carried out on 10-year-old plants of 8 V. vinifera cvs: 'Sauvignon Blanc', 'Chardonnay', 'Cabernet Sauvignon', 'White Grenache', 'Black Grenache', 'Alicante Bouschet', 'Tempranillo', and 'Parellada' grown under field conditions without irrigation under Mediterranean climatic conditions. Embolism vulnerability curves were drawn for each cultivar. Values of the osmotic potential at full turgor, and at the turgor loss point, and the leaf bulk modulus of elasticity were obtained from pressure-volume curves on 4 different dates, from berries at pea size until harvest. All cultivars except 'Chardonnay', which showed elastic adjustment, showed osmoregulation but different patterns in vulnerability curves were found for each cultivar. While 'Parellada', 'Tempranillo' and 'Black Grenache'; proved to have the most vulnerable xylem, 'Chardonnay' and 'Sauvignon Blanc' were shown to have the least vulnerable xylem to embolism. There was no relationship between the level of vulnerability to embolism for each cultivar and the drought tolerance mechanisms at the leaf level under the environmental conditions of this experiment.