E.A. Bacelar

Physiological behaviour, oxidative damage and antioxidative protection of olive trees grown under different irrigation regimes

Irrigation effects were investigated on an 8-year-old olive (Olea europaea L., cv. Cobrançosa) commercial orchard located in northeast Portugal. Trees were subjected to a rainfed control (T0) and three treatments (T1, T2, T3) that received a seasonal water amount equivalent to 30%, 60% and 100% of the estimated local evaporative demand by a drip irrigation system. Irrigation increases the photosynthetic activity of olive trees, in association with increases in water status, and reduces the midday and afternoon depression in gas exchange. The closely association between photosynthetic rate (A) and stomatal conductance (gs) revealed that the decline in net photosynthesis over the course of the day was largely a consequence of stomatal limitation. However, the ratio of intercellular to atmospheric CO2 concentration increased markedly from morning to midday in non-irrigated plants, in spite of lower gs, suggesting that non-stomatal limitations of photosynthesis also occur when environmental conditions become more stressful. The occurrence of perturbations at chloroplastic level in rainfed plants was demonstrated by a lower maximum photochemical efficiency of photosystem II during the afternoon. Chlorophyll fluorescence measurements also revealed the occurrence of a dynamic photoinhibition in irrigated trees, mainly in T2 and T3, which seemed to be effective in protecting the photosynthetic apparatus from photodamage. Irrigation enhances antioxidant protection and decreases the oxidative damage at leaf level. Leaves grown under rainfed conditions revealed symptoms of oxidative stress, like the reduction (14%) in chlorophyll concentration and the increased levels (57%) of lipid peroxidation. We also found that the scavenging function of superoxide dismutase was impaired in rainfed plants. In contrast, the low thiobarbituric acid reactive substances concentration in T3 indicates that irrigation enhances the repairing mechanisms and decreases the oxidative damage by lipid peroxidation. Accordingly, leaves in T3 treatment had high levels of –SH compounds and the highest antioxidant potential. Meanwhile, the finding that guaiacol peroxidase activity increased in rainfed plants, associated with the appearance of oxidative damage, suggests that this enzyme has no major antioxidative function in olive.

Leaf Gas Exchange and Water Relations of Grapevines Grown in Three Different Conditions

Diurnal and seasonal changes in the leaf water potential (Ψ), stomatal conductance (gs), net CO2 assimilation rate (PN), transpiration rate (E), internal CO2 concentration (Ci), and intrinsic water use efficiency (PN/gs) were studied in grapevines (Vitis vinifera L. cv. Touriga Nacional) growing in low, moderate, and severe summer stress at Vila Real (VR), Pinhão (PI), and Almendra (AL) experimental sites, respectively. In VR and PI site the limitation to photosynthesis was caused more by stomatal limitations, while in AL mesophyll limitations were also responsible for the summer decline in PN.

Effects of elevated CO2 on grapevine (Vitis vinifera L.): volatile composition, phenolic content, and in vitro antioxidant activity of red wine.

The impact of elevated carbon dioxide concentration ([CO2]) on the quality of berries, must, and red wine (with special reference to volatile composition, phenolic content, and antioxidant activity) made from Touriga Franca, a native grape variety of Vitis vinifera L. for Port and Douro wine manufacturing grown in the Demarcated Region of Douro, was investigated during 2005 and 2006. Grapevines were grown either in open-top chambers (OTC) with ambient (365 +/- 10 ppm) or elevated (500 +/-16 ppm) [CO2] or in an outside plot. In general, the increase of [CO2] did not affect berry characteristics, especially the total anthocyan and tannin concentrations. However, the total anthocyan and polyphenol concentrations of the red wine were inhibited under elevated [CO2]. The antioxidant capacity of the wines was determined by DPPH, ABTS, and TBARS assays and, despite the low concentrations of phenolics, the elevated [CO2] did not significantly change the total antioxidant capacity of the red wines. Thirty-five volatile compounds belonging to seven chemical groups were identified: C6 alcohols, higher alcohols, esters, terpenols, carbonyl compounds, acids, volatile phenols, and C13 norisoprenoids. Generally, the same volatile compounds were present in all of the wines, but the relative levels varied among the treatments. The effect of elevated [CO2] was significant because it was detected as an increase in ethyl 2-methylbutyrate, isoamyl acetate, ethyl hexanoate, ethyl octanoate, butyric acid, and isovaleric acid concentrations and a decrease in ethyl acetate concentration when compared to wines produced in ambient [CO2] in 2005. In elevated [CO2], wines from 2006 had lower methionol, 1-octanol, and 4-ethylguaiacol and higher ethyl lactate and linalool concentrations. The increase in [CO2] did not significantly affect C6 alcohols, citronellol, carbonyl compounds, and beta-damascenone concentrations. This study showed that the predicted rise in [CO2] did not produce negative effects on the quality of grapes and red wine. Although some of the compounds were slightly affected, the red wine quality remained almost unaffected.

Physiological responses of different olive genotypes to drought conditions

Gas exchange rates, chlorophyll fluorescence, pressure–volume relationships, photosynthetic pigments, total soluble sugars, starch, soluble proteins and proline concentrations were investigated in five Olea europaea L. cultivars with different geographical origins (Arbequina, Blanqueta, Cobrançosa, Manzanilla and Negrinha) grown under Mediterranean field conditions. We found considerable genotypic differences among the cultivars. Comparing the diurnal gas exchange rates, we observed that Cobrançosa, Manzanilla and Negrinha had high photosynthetic rate than Arbequina and Blanqueta. The first group reveals to be better acclimated to drought conditions, and appears to employ a prodigal water-use strategy, whereas Blanqueta and Arbequina, with high water-use efficiency, appear to employ a conservative water-use strategy. The degree of midday depression in photosynthesis was genotype dependent, with a maximum in Arbequina and a minimum in Negrinha. The reductions in the photosynthetic rate were dependent from both stomatal and non-stomatal limitations. Elastic adjustment plays an important role as drought tolerance mechanism. The group of cultivars that employ a prodigal water-use strategy revealed high tissue elasticity, whereas Arbequina and Blanqueta revealed high tissue rigidity. We also identified the existence of drought tolerance mechanisms associated with soluble proteins accumulation in the foliage. The high levels of soluble proteins in Arbequina may represent an increased activity of oxidative stress defence enzymes and may also represent a reserve for post stress recovery. In all cultivars, especially in Manzanilla, free proline was accumulated in the foliage. The discussed aspects of drought stress metabolism may have an adaptative meaning, supporting the hypothesis that olive cultivars native to dry regions, such as Cobrançosa, Manzanilla and Negrinha, have more capability to acclimate to drought conditions than cultivars originated in regions with a more temperate climate, like Arbequina and Blanqueta.

Gas exchange and water relations of three Vitis vinifera L. cultivars growing under Mediterranean climate

Optical characteristics, contents of photosynthetic pigments, total soluble sugars, and starch, rates of gas exchange, chlorophyll (Chl) a fluorescence, and leaf water relations were analysed in three Vitis vinifera L. cultivars, Tinto Cão (TC), Touriga Nacional (TN), and Tinta Roriz (TR), grown in Mediterranean climate. Chl content was significantly lower in TC than in TN and TR leaves, while the Chl a/b ratio was higher. TR had the lowest net photosynthetic rate, stomatal conductance, and contents of soluble sugars and starch than TN and TC. In spite of low Chl content, TC showed the lowest photon absorbance and the highest photochemical efficiency of photosystem 2. TC had the lowest predawn and midday leaf water potential. The capability for osmotic adjustment was similar among cultivars and the calculated modulus of elasticity was higher in TC leaves. The typical lighter green leaves of TC seemed to be an adaptive strategy to high irradiance and air temperature associated to water stress.

Ultraviolet-B radiation and nitrogen affect nutrient concentrations and the amount of nutrients acquired by above-ground organs of maize

UV-B radiation effects on nutrient concentrations in above-ground organs of maize were investigated at silking and maturity at different levels of applied nitrogen under field conditions. The experiment simulated a 20% stratospheric ozone depletion over Portugal. At silking, UV-B increased N, K, Ca, and Zn concentrations, whereas at maturity Ca, Mg, Zn, and Cu increased and N, P and Mn decreased in some plant organs. Generally, at maturity, N, Ca, Cu, and Mn were lower, while P, K, and Zn concentrations in stems and nitrogen-use efficiency (NUE) were higher in N-starved plants. UV-B and N effects on shoot dry biomass were more pronounced than on nutrient concentrations. Nutrient uptake decreased under high UV-B and increased with increasing N application, mainly at maturity harvest. Significant interactions UV-B x N were observed for NUE and for concentration and mass of some elements. For instance, under enhanced UV-B, N, Cu, Zn, and Mn concentrations decreased in leaves, except on N-stressed plants, whereas they were less affected by N nutrition. In order to minimize nutritional, economical, and environmental negative consequences, fertiliser recommendations based on element concentration or yield goals may need to be adjusted.

Water Use Strategies of Plants Under Drought Conditions

The growing concerns about water scarcity have focused more attention on water management in agriculture and promotion of water conservation through improved water use efficiency (WUE). Depending on the main purpose of the study, WUE can be estimated at multiple scales, from leaf to whole plant, crop, yield, and ecosystem levels. Drought resistance and WUE are not synonymous and their association is often misunderstood. Effectively, two water use strategies may be employed by woody plants under drought conditions. The prodigal water use behavior is beneficial in conditions where water supply is interrupted for short periods only. The conservative water use is favorable in conditions where a long dry period prevails and is associated with high capacity for drought resistance and slow growth rates. In this chapter, we also examine how human manipulation such as breeding and agricultural management techniques will offer new opportunities to improve plant water use under drought conditions.

Evaluation of chemical and phenotypic changes in Blanqueta, Cobrançosa, and Galega during olive fruits ripening

Olea europaea L. presents a huge number of cultivars that differ in terms of end-use, and consequently in their chemical composition. The use of different phenotypic (fruit dimension, shape, and color) and chemical parameters (phenolic compounds, flavonoids, and antioxidant activity) during olive fruit maturation in three olive cultivars (Blanqueta, Cobrançosa, and Galega), grown in the Protected Denomination Region of Trás-os-Montes, revealed clear differences among the cultivars, indicating that they behave differently during the maturation process, Galega being the first to reach full maturity. All colorimetric parameters (L*, b*, C*, and H*) decreased with maturity. Galega cultivar presented the highest phenolic content in all the maturation stages analyzed (128.25–175.46 mg GAE g−1). Also, this cultivar presented the highest antioxidant activity in semi-green stage fruits (231.72 μmol Trolox g−1). The flavonoid content increased in all cultivars from the green drupe to black stage, with differential behavior between the cultivars within maturation stages. Moreover, a high correlation was found between the phenolic compounds content and the antioxidant activity levels.

Response, Tolerance and Adaptation to Abiotic Stress of Olive, Grapevine and Chestnut in the Mediterranean Region: Role of Abscisic Acid, Nitric Oxide and MicroRNAs

Hot, dry summers and mild to cool, wet winters are the characters of the Mediterranean climate. Drought, extreme temperatures and extreme irradiation (UVs) often concomitantly in some cases also together with salinity, significantly affect the growth, yield and quality of the Mediterranean crops. Olive (Olea europaea L), grapevine (Vitis vinifera L) and sweet chestnut (Castanea sativa) are the most important woody crops in the Mediterranean among others. The olive tree and vineyard are familiar features of the Mediterranean landscape. In some mountain regions, these features are accompanied by the orchards of chestnut. Olive oil and wine are important products in that region. In some regions, such as Italy, Turkey, Spain, Portugal, and Greece, chestnut is one of the most important fruit products as well. Olive oil, grape and wine are a traditional icon of the Mediterranean diet. Enjoying the plentiful indigenous plant products, especially wine, olive oil and chestnut, is part of the Mediterranean civilization. Olive oil is the main source of fat in the Mediterranean diet and one of those basic ingredients essential to life in the Mediterranean. It may also protect against heart disease, stroke, and certain cancers. The vine and wine are among the most important symbols of

Morphometrics and chemometrics as tools for medicinal and aromatic plants characterization

The characterization of commercialized and consumed plants is of extreme importance, in order to provide clear data regarding the quality of plants, but also concerning the intake, by consumers, of several important compounds present is those plants. Hence, the objective of this work was to provide a detailed morphological and biochemical description of commercial samples of five common medicinal and aromatic plants (MAP’s) ( Coriandrum sativum L. –coriander, Mentha spicata L. – spearmint, Ocimum basilicum L. – basil, Origanum vulgare L. – oregano and Petroselinum crispum Mill. – parsley). For the studied species, statistically significant differences were evident for all the morpho-analytical characteristics investigated, as well as for the majority of the evaluated biochemical parameters. Specific leaf area was higher in Coriandrum sativum , while the water content of the leaves of Ocimum basilicum was the highest. Regarding photosynthetic pigments, when statistical differences were detected, these indicated the presence of larger amounts of chlorophyll and carotenoids in the leaves of Coriandrum sativum and Petroselinum crispum . Carbohydrate quantification indicated a considerably higher content in Petroselinum crispum , which also contained higher concentrations of protein, together with Coriandrum sativum . Quantification of total phenolic and thiobarbituric acid reactive substances indicated that they were correlated, with leaves of Mentha spicata presenting the highest values, on both parameters. This work provides an overview of selected characteristics of MAP’s that are available for purchase, and are actually consumed by consumers. Data are publicly available from the open access repository OpenAgrar, doi: 10.5073/openagrar.2017.000001 .