Leaf-level morphological and structural adaptations to reduce water loss were examined in five olive (Olea europaea L.) tree cultivars (Arbequina, Blanqueta, Cobrançosa, Manzanilla and Negrinha) growing under field conditions with low water availability. Leaf measurements included leaf tissue thickness, stomatal density, leaf area, leaf mass per unit area, density of leaf tissue, relative water content, succulence, water saturation deficit, water content at saturation and cuticular transpiration rate. We found considerable genotypic differences among the cultivars. Negrinha, Manzanilla and Cobrançosa had more morphological and structural leaf adaptations to protect against water loss than the other cultivars. Manzanilla and Negrinha enhanced their sclerophylly by building parenchyma tissues and increasing protective structures like the upper cuticle and both the upper and lower epidermis. Cobrançosa exhibited good protection against water loss through high density of foliar tissue and by thick cuticle and trichome layers. Compared with the Negrinha, Manzanilla and Cobrançosa cultivars, Arbequina leaves had a thinner trichome layer, implying that the leaves were less protected against water loss; however, the development of smaller leaves may reduce water loss at the whole-plant level. Among cultivars, Blanqueta had the largest leaves and some anatomical traits that may lead to high water loss, especially from the adaxial surface. The mechanisms employed by the cultivars to cope with summer stress are discussed at the morpho-structural level.

Water relations, leaf gas exchange, chlorophyll a fluorescence, light canopy transmittance, leaf photosynthetic pigments and metabolites and fruit quality indices of cherry cultivars 'Burlat', 'Summit' and 'Van' growing on five rootstocks with differing size-controlling potentials that decrease in the order: Prunus avium L. > CAB 11E > Maxma 14 > Gisela 5 > Edabriz, were studied during 2002 and 2003. Rootstock genotype affected all physiological parameters. Cherry cultivars grafted on invigorating rootstocks had higher values of midday stem water potential (Psi(MD)), net CO(2) assimilation rate (A), stomatal conductance (g(s)), intercellular CO(2) concentration (C(i)) and maximum photochemical efficiency of photosystem II (PSII) (F(v)/F(m)) than cultivars grafted on dwarfing rootstocks. The Psi(MD) was positively correlated with A, g(s) and C(i). Moreover, A was positively correlated with g(s), and the slopes of the linear regression increased from invigorating to dwarfing rootstocks, indicating a stronger regulation of photosynthesis by stomatal aperture in trees on dwarfing Edabriz and Gisela 5. The effect of rootstock genotype was also statistically significant for leaf photosynthetic pigments, whereas metabolite concentrations and fruit physicochemical characteristics were more dependent on cultivar genotype. Among cultivars, 'Burlat' leaves had the lowest concentrations of photosynthetic pigments, but were richest in total soluble sugars, starch and total phenols. Compared with the other cultivars, 'Summit' had heavier fruits, independent of the rootstock. 'Burlat' cherries were less firm and had lower concentrations of soluble sugars and a lower titratable acidity than 'Van' cherries. Nevertheless, 'Van' cherries had lower lightness, chroma and hue angle, representing redder and darker cherries, compared with 'Summit' fruits. In general, Psi(MD) was positively correlated with fruit mass and A was negatively correlated with lightness and chroma. These results demonstrate that: (1) water relations and photosynthesis of sweet cherry tree are mainly influenced by the rootstock genotype; (2) different physicochemical characteristics observed in cherries of the three cultivars suggest that regulation of fruit quality was mainly dependent on the cultivar genotype, although the different size-controlling rootstocks also had a significant effect.

No abstract

Climate change is a major challenge to viticulture worldwide. The adaptation potential of the different strategies to cope with climate change still embraces many uncertainties (e.g., unpredictable social-economic developments and land-use changes), particularly in the long-term. However, adaptation strategies adjusted to local terroirs and regional climate change projections will contribute to the sustainable development of the winemaking sector. The Clim4Vitis action (https://clim4vitis.eu/) recommends some guidelines for long-term adaptation (Figure 1).

Viticulture is exposed and vulnerable to extreme weather and climate change. In Europe, owing to the high socio-economic value of the winemaking sector, the development of adaptation strategies to mitigate climate change impacts will be of foremost relevance for its future sustainability and competitiveness. Some guidelines on feasible short-term adaptation strategies are provided here (Figure 1), collected by the Clim4Vitis action (https://clim4vitis.eu/). Long-term adapation startegies are described in an accompanying technical review.