Crop yield response to water - Cra

In common with most crops, tissue expansion in grapevine is more sensitive to water deficit thanstomatal regulation and gas exchange (Figure 5a-d). The effects of intensity and duration ofwater stress have been integrated in stress indices based, for example, on soil water status (Figure5a-d), plant-water status or canopy temperature (Figure 6). Box 2 summarizes techniques usedto monitor water status of vines, and below analyses yield response to water deficit from theperspective of production functions.Owing to the developmental programme of the plant and the definition of yield over twoconsecutive seasons, we need to consider the effects of water deficits in the previous season on thegrowth and yield in the current season. All possible responses have been reported, namely effectsFIGURE 5 Scheme for water management derived for Shiraz, Grenache and Mourvèdre in southernFrance. Relationships between fraction of transpirable soil water (FTSW) and the rate of(a) light-saturated net photosynthesis; leaf emergence rate in (b) first-, or (c) second-order lateralbranches, and (d) final length of first-order lateral branches. Rates measured in water-deficittreatments are normalized with respect to well-watered controls. The boxes (0 to 7) representeight classes with characteristic impairment of plant function by drying soil; for instance in (a)light saturated photosynthesis is above 80 percent of controls in classes 0 to 3, and is reduced to60, 40, 20 and 7 percent of controls as soil dries from classes 4 to 7. The table shows recommendedlevel of water stress (FTSW class) for quality red wine production at different phenological stages.Adapted from Pellegrino et al. (2006).aAnnax(% of control)120100806040200 to 33 4567Phenophase(E-L stage)Budburst to flowering(4 to 23)FTSW class forquality red wineproduction0 to 1bLER I(% of control)01201008060402000 1 2345Flowering to bunch closure(23 to 32)Bunch closure to veraison(32 to 35)Veraison to harvest(35 to 38)235 to 66 77120cLER II(% of control)1008060402000123456dBLI(% of control)1201000180260402001.0 0.8 0.63456 70.4 0.2 0.0FTSWgrapevine 467