Long-term observations in Napa Valley and Bordeaux reveal that grapevines never reach a lethal level of drought.

No abstract

<p style="text-align: justify;">Water is an important factor in the terroirs of grape-growing regions. The vine obtains water from rainfall and the water table and when it is in short supply, it is necessary either to irrigate or accept the effects of water stress. Depending on the intensity of the water stress and the period at which it occurs, it may or not be favourable for the harvest and the wine it is used to produce. The objective of this article is to provide some information on the relationship that exists between the vine and water. The climate and the soil, which are essential but not the sole elements of this relationship will only be touched upon, but we will discuss in a non exhaustive way, with information’s from the bibliography or from our research, the following aspects: the root system, vegetative growth, the relationship between plant architecture and the water status of the vine, the carbon balance and the biochemical composition of the grape berry in relation to vine water status. We will also present the currently available techniques for measuring vine water status and its evolution during the vegetative cycle as a function of water reserves in the soil easy to use by the roots. Finally examples are presented of possible recommendations for vine cultural practices as a function of the vine water status evolution during the growth, according to the predawn leaf water potential thresholds.</p>

Abstract. The goal of this study was to test the usefulness of high-spatial resolution information provided by airborne imagery and soil electrical properties to define plant water restriction zones within-vineyards. The main contribution of this is to propose a study on a large area representing the regions' vineyard diversity (different age, different varieties and different soils) located in southern France (Languedoc-Roussillon region, France). Nine non-irrigated plots were selected for this work in 2006 and 2007. In each plot, different zones were defined using the high-spatial resolution (1m 2 ) information provided by airborne imagery (Normalised Difference Vegetation Index, NDVI). Within each zone, measurements were conducted to assess: (i) vine water status (Pre-dawn Leaf Water Potential, PLWP), (ii) vine vegetative expression (vine trunk circumference and canopy area), (iii) soil electrical resistivity and, (iv) harvest quantity and quality. Large differences were observed for vegetative expression, yield and plant water status between the individual NDVI-defined zones. Significant differences were also observed for soil resistivity and vine trunk circumference, suggesting the temporal stability of the zoning and its relevance to defining vine water status zones. The NDVI zoning could not be related to the observed differences in quality, thus showing the limitations in using this approach to assess grape quality under non-irrigated conditions. The paper concludes with the approach that is currently being considered: using NDVI zones (corresponding to plant water restriction zones) in association with soil electrical resistivity and plant water status measurements to provide an assessment of the spatial variability of grape production at harvest.