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Changes in L-phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) activity and total phenolic, ortho-diphenolic and fat contents of olive¯esh in response to different irrigation treatments applied to olive tree cv Arbequina were studied during fruit ripening. Results indicate that the fat content of olivē esh at harvest was not affected by irrigation, although olives from the most heavily irrigated treatment reached their ®nal fat content (dry weight) earlier than those from other irrigation treatments. PAL activity and phenolic content, expressed on a dry weight basis, decreased during fruit development and were affected by irrigation, being lowered as the water supplied increased. Good correlations were established between PAL enzymatic activity and the polyphenol and ortho-diphenol contents of olive¯esh, indicating that PAL is involved in the phenolic metabolism of olive fruit. The phenolic content of the oil depends on the PAL activity in the fruit, which varies with changes in water status.

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This study evaluated the effects of different regulated deficit irrigation (RDI) strategies applied to olive (Arbequina cultivar) trees on the qualitative and quantitative parameters of the resulting oil during the maximum evaporative demand period for three consecutive crop seasons. Quality indices, fatty acid composition, pigments, colour, a-tocopherol and phenolic contents, bitter index, oxidative stability and organoleptic properties of the oil were determined. Irrigation did not affect those parameters used as criteria for classifying olive oil in its commercial grades. Only polyphenol and o-diphenol contents and, consequently, the bitter index and oxidative stability were affected by the RDI strategy, with increasing values as the water applied decreased. Regulated deficit irrigation resulted in important savings in irrigation requirements without detriment to oil quality.

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Background and Aims: The effect of water stress on berry quality is not fully understood. This study was designed to analyse the differential phenological sensitivity of Tempranillo berry quality to water stress during three phenological stages. Methods and Results: Two-year-old potted Tempranillo vines were exposed to four levels of irrigation (100, 50, 25, and 0% of evapotranspiration) during three phenological stages (Stage I, from anthesis to fruitset; Stage II, pre-veraison; Stage III, post-veraison). Vine water status was monitored by means of leaf water potential measurements. Berry quality was measured at harvest and defined by the following parameters: berry dry weight, soluble solids content, titratable acidity, polyphenol and anthocyanin concentrations in the must. Berry dry-matter accumulation was more sensitive to water stress applied during Stage I and Stage II than in Stage III. Berry quality tended to decrease linearly with increasing water stress during Stage II. During Stage III, berry quality increased linearly for light-to-mild levels of water stress, whereas quality decreased above a certain water-stress threshold (Yleaf = -1.12 MPa). Conclusions: Tempranillo berry quality demonstrated great phenological sensitivity to water stress. Pre-veraison water stress negatively affected berry quality in Tempranillo vines, whereas post-veraison water stress increased quality up to a certain threshold of Yleaf. Significance of the Study: For the first time, this research reports a plant-based water status threshold in Tempranillo vines above which post-veraison water stress can negatively affect berry quality. 268Sensitivity of Tempranillo to water stress

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