In the present study, field grown Aragonez (Syn. Tempranillo) grapevines (Vitis vinifera L.) were subjected to three irrigation regimes (conventional sustained deficit irrigation (DI), regulated deficit irrigation (RDI) and non-irrigated (NI)) during two successive seasons (2007-2008). An integrative study was performed in grape berry skin tissues at four phenological stages of grape berry (pea size, véraison, mid-ripening and full maturation). The accumulation of flavonoid compounds, the profile of accumulation of abscisic acid (ABA) and jasmonic acid (JA) hormones were analysed during grape ripening. The non-enzymatic antioxidant capacity was also characterised. Principal component analysis followed by a between group analysis (PCA-BGA) showed a clear separation already at early stages of grape berry development between the three treatments in both years. The main compounds affected by water availability were proanthocyanidins and flavonols, which increased with irrigation at all phenological stages. In both years, concentrations of anthocyanin at full maturation were observed to be higher in the skin of berries belonging to DI and RDI vines than in NI ones. ABA accumulation was also regulated by the intensity of water stress since early stages of berry development. However, no differences in sugar accumulation were observed between treatments. The present study also shows that climatic conditions, namely temperature, play an important role in the ripening process of grape berries. This was clearly observed in NI vines during both years, in which a decrease in the quality parameters in grape skins is presumably related to high temperature and excessive cluster sunlight exposition more marked in 2007, the hotter year. This supports the crucial role of irrigation in maintaining the cluster microclimate in an optimum range, thus enabling a balanced synthesis of the compounds relevant to wine quality.

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Eucalyptus plantations are among the most productive forest stands in Portugal and Spain, being mostly used for pulp production and, more recently, as an energy crop. However, the region's Mediterranean climate, with characteristic severe summer drought, negatively affects eucalypt growth and increases mortality. Although the physiological response to water shortage is well characterized for this species, evidence about the plants' recovery ability remains scarce. In order to assess the physiological and biochemical response of Eucalyptus globulus during the recovery phase, two genotypes (AL-18 and AL-10) were submitted to a 3-week water stress period at two different intensities (18 and 25% of field capacity), followed by 1 week of rewatering. Recovery was assessed 1 day and 1 week after rehydration. Drought reduced height, biomass, water potential, NPQ and gas exchange in both genotypes. Contrarily, the levels of pigments, chlorophyll fluorescence parameters (F(v) /F(m) and (φPSII)), MDA and ABA increased. During recovery, the physiological and biochemical profile of stressed plants showed a similar trend: they experienced reversion of altered traits (MDA, ABA, E, g(s), pigments), while other parameters did not recover ((φPSII), NPQ). Furthermore, an overcompensation of CO(2) assimilation was achieved 1 week after rehydration, which was accompanied by greater growth and re-establishment of oxidative balance. Both genotypes were tolerant to the tested conditions, although clonal differences were found. AL-10 was more productive and showed a more rapid and dynamic response to rehydration (namely in carotenoid content, (φPSII) and NPQ) compared to clone AL-18.

The photosynthesis source–sink relationship in young Pinus canariensis seedlings was modified by stem girdling to investigate sprouting and cambial activity, feedback inhibition of photosynthesis, and stem and root hydraulic capacity. Removal of bark tissue showed a trade-off between sprouting and diameter growth. Above the girdle, growth was accelerated but the number of sprouts was almost negligible, whereas below the girdle the response was reversed. Girdling resulted in a sharp decrease in whole plant transpiration and root hydraulic conductance. The reduction of leaf area after girdling was strengthened by the high levels of abscisic acid found in buds which pointed to stronger bud dormancy, preventing a new needle flush. Accumulation of sugars in leaves led to a coordinated reduction in net photosynthesis (AN) and stomatal conductance (gS) in the short term, but later (gS below 0.07 mol m-2 s-1) AN decreased faster. The decrease in maximal efficiency of photosystem II (FV/FM) and the operating quantum efficiency of photosystem II (ΦPSII) in girdled plants could suggest photoprotection of leaves, as shown by the vigorous recovery of AN and ΦPSII after reconnection of the phloem. Stem girdling did not affect xylem embolism but increased stem hydraulic conductance above the girdle. This study shows that stem girdling affects not only the carbon balance, but also the water status of the plant.

Here, we provide the first report on flavonoid content in holm oak (Quercus ilex L.) leaves, analyzed by HPLC-MS/MS. Flavanols and flavonols were the predominant groups, although proanthocyanidins and many soluble tannins had a relevant presence in all leaf samples. Seasonal variation of flavonoids was determined in extracts from Q. ilex leaves during resprouting after a forest fire in two Mediterranean forests. Similar seasonal trends were observed over 2 years during the two main stress seasons (winter and summer). The most abundant flavonoid was the flavanol epicatechin, which showed similar values during the two seasons. Hexosides of the flavonols, quercetin, kaempferol and rhamnetin showed considerably higher content in winter, especially at the lowest temperatures. These variations in both forests are discussed on the basis of the chlorophyll fluorescence results obtained. Anthocyanins were found practically absent in mature leaves. Nutrient or water availability differences between sites or seasons were not related to changes in leaf flavonolhexoside content.