Rootstock effects on the adaptive strategies of grapevine (Vitis vinifera L. cv. Cabernet–Sauvignon) under contrasting water status: Leaf physiological and structural responses

The effects of two rootstocks (1103P and SO4) on water status, gas exchange, leaf structural characteristics and vine growth were studied in a factorial experiment over 2 years (2005–2006), in field-grown grapevines of cv. Cabernet–Sauvignon (Vitis vinifera L.), subjected to three irrigation levels (FI: 100% of evapotranspiration, DI: 50% of evapotranspiration and NI: not irrigated). The experiment was conducted on 10-year-old vines, grown under the semi-arid conditions of central Greece. There was a significant depressive effect in water status (estimated by midday stem water potential, Ψs) and net assimilation rate (A) of Cabernet–Sauvignon with decreasing water supply, on both rootstocks. The down regulation of A was mainly due to decreases in stomatal conductance (gs). NI treatment showed significantly higher intrinsic water use efficiency (A/gs) and lower leaf carbon isotope discrimination (Δ) compared to irrigated treatments. Leaf area index (LAI) and pruning weight (PW) were found to be higher under FI treatment but this effect was more pronounced on the 1103P-grafted vines. Canopy growth was strongly controlled by rootstock, being significantly higher on 1103P, presumably due to its higher capacity to access soil water. Rootstock genotype affected scion water status via its effect on whole-vine transpiration. Cabernet–Sauvignon photosynthesis response to water status was not altered by rootstock. The only apparent difference between rootstocks was the higher A of SO4-grafted vines under NI treatment, associated with higher Ψs. A/gs and Δ were only altered under FI treatment, with 1103P showing more efficient use of available soil water than SO4. Vines on SO4 had a lower specific leaf area (SLA) as a result of lower growth rate than 1103P, which possibly provided a supplemental mechanism to maintain leaf water status and gas exchange. Concluding, SO4 could be better adapted on fertile soils under non-limiting water supply due to its capacity to achieve a balanced vegetative and reproductive growth while 1103P, a more water efficient rootstock, would be better to grow in semi-arid regions where water limitation occurs.