EFFECT OF DROUGHT AND HEAT ON VINE PHYSIOLOGY AND GRAPE RIPENING

Certain vintages reveal the effects of environmental constraints. This was the case in 2003 (editor’s note: in France), when drought and heat combined and forced vines to undergo exceptional adaptations, or exposed their inability to adapt to the situation. Many think that such a situation was exceptional, even if some analogies can be found in the past, some of which, over a century ago. Without doubt, reality gives another account: For about 20 years, both climatologists and viticulturists have observed the effects of a global climate change leading to prematurity, as much as a temperature increases during the ripening period with higher maxima in numerous viticultural areas. Although in inconsistent pattern, these phenomena go along with greater variations of the water availability and with particularly severe summer droughts, which are often framed by violent precipitations, particularly in Autum in the Mediterranean. Thus, the knowledge acquired in 2003 constitutes an investment for some vintages to come. Regarding the vine ecophysiology, the major effects of drought and heat are quite well understood. However, the adaptation of viticultural decisions should be even better handled, specifically vineyard management and qualitative irrigation. Moreover, as for the understanding of the effect of “terroirs”, the consequences of such events on grape physiology, biochemistry and genomics are rather incomplete. Similar observations affect the sensory analysis of wines. In this context, it is useful to review the principles, which result from the energy balance of vineyards. Solar energy collected in the vineyard can be divided into several elements.