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Mature leaves are the primary source of sugars, which give rise to many secondary metabolites required for plant survival under adverse conditions. In order to study the interaction of field-grown cork oak (Quercus suber L.) with the environment, we investigated the seasonal variation of minerals and organic metabolites in the leaves, using inductively coupled plasma atomic emission spectrometry, elemental analysis and nuclear magnetic resonance spectrometry. Statistical analysis showed that the data strongly correlated with seasonal climate and were divided in three groups corresponding to: (1) spring-early summer, (2) summer and (3) autumn-winter. The concentration of N, P, K and leaf ash content were highest in spring (recently formed leaves), reached the minimum during the hot and dry summer and increased slightly during the rainy period of autumn-winter. Conversely, Na, Mg and Ca concentrations were lowest in spring-early summer and increased during summer and autumn-winter, the Ca concentration increasing five-fold. Two cyclitol derivatives, quinic acid and quercitol were the major organic metabolites of the leaves. Their concentration along the season followed opposite trends. While quinic acid predominated during spring-early summer, when it contributed 12% to the leaf osmotic potential, quercitol was predominant during autumn-winter, when its contribution to leaf osmotic potential was about 10%. This different preponderance of the two compounds is expressed by the quercitol/quinic acid ratio, which can be as low as 0.2 in early summer and as high as 9 in winter. Sucrose and glucose concentrations also increased during autumn-winter. Evidence for the quercitol protective role in plants during stress is discussed, and on the basis of structural similarity, it is suggested that quinic acid could have an identical importance, with a protective role against heat and high irradiance. It is concluded that the marked changes in Q. suber leaf composition throughout the year could have important implications in the plant capacity to endure climatic stress.

Drought was induced in chickpea (Cicer arietinum L.) genotypes (ChK 3226 and ILC 3279) differing in yield capacity. Water stress (S1, RWC around 55-50%; S2, RWC ≤ 40%) drastically reduced stomatal conductance (g s ) and net photosynthetic rate (P N ) in both genotypes. ILC 3279 showed greater photosynthetic capacity (A max ) decreases. Maximum PSII photochemical efficiency (F v /F m ), photochemical quenching (q P ), total chlorophylls (Chls) and carotenoids (Cars) content showed stability in both genotypes under stress, but in S2 ILC 3279 presented an increase in basal fluorescence (F 0 ) and a greater reduction in estimation of quantum yield of linear electron transport (Φ e ) than ChK 3226. Membrane damage evaluated by electrolyte leakage occurred earlier and was greater in ILC 3279. It also presented a decrease of total fatty acids (TFA) along drought, while in ChK 3226 greater amounts of TFA were observed in S1. In rehydration, P N of S1 plants completely recovered (ILC 3279) or remained slightly below control (ChK 3226). As regards S2 plants, ILC 3279 showed stronger P N and g s reductions than ChK 3226, despite both genotypes totally recovered A max and chlorophyll (Chl) a fluorescence. ChK 3226 recovered more efficiently from membrane damage. Under control conditions, greater amounts of most of the studied soluble metabolites occurred in ChK 3226 plants. Malate and citrate decreased with water stress (S2) in both genotypes. Sucrose and pinitol (that had a higher concentration than sucrose in both genotypes) increased in ILC 3279 (S1 and S2), and decreased in ChK 3226 (S2). In ILC 3279 proline and asparagine followed similar patterns. Genotypes showed a similar shoot dry mass (DM) in control plants, but root DM was higher in ChK 3226. Drought reduced root and shoot DM in ChK 3226 already under S1, while in ILC 3279 root DM was unaffected by drought and shoot biomass decreased only in S2. Root/shoot ratio was always higher in ChK 3226 but tended to decrease under stress, while the opposite was observed in ILC 3279. No pods were obtained from control plants of both genotypes, or droughted ILC 3279 plants. ChK 3226 produced pods under S1 (higher yield) and S2. Under stress conditions, ChK 3226 was less affected in photosynthetic activity and membrane integrity, showing a better tolerance to drought. This agrees with the better yield of this genotype under water stress. Distinct strategies seem to underlie the different physiological responses of the two genotypes to water deficit. In spite of its significant solutes accumulation, ILC 3279 was more affected in photosynthetic activity and membrane integrity during water stress than ChK 3226, which showed better yield under drought. A relation could not be established between solutes accumulation of ILC 3279 and yield.Additional key words: chlorophyll fluorescence, electrolyte leakage, membrane lipids, water stress. -net photosynthetic rate; Pro -proline; q P -photochemical quenching; Rec -recovery; R D -dark respiration rate; RWC -relative water content; Suc -s...

Grape berries (Vitis vinifera L fruit) exhibit a double-sigmoid pattern of development that results from two successive periods of vacuolar swelling during which the nature of accumulated solutes changes significantly. Throughout the first period, called green or herbaceous stage, berries accumulate high levels of organic acids, mainly malate and tartrate. At the cellular level fruit acidity comprises both metabolism and vacuolar storage. Malic acid compartmentation is critical for optimal functioning of cytosolic enzymes. Therefore, the identification and characterization of the carriers involved in malate transport across sub-cellular compartments is of great importance. The decrease in acid content during grape berry ripening has been mainly associated to mitochondrial malate oxidation. However, no Vitis vinifera mitochondrial carrier involved in malate transport has been reported to date. Here we describe the identification of three V. vinifera mitochondrial dicarboxylate/tricarboxylate carriers (VvDTC1-3) putatively involved in mitochondrial malate, citrate and other di/tricarboxylates transport. The three VvDTCs are very similar, sharing a percentage of identical residues of at least 83 %. Expression analysis of the encoding VvDTC genes in grape berries shows that they are differentially regulated exhibiting a developmental pattern of expression. The simultaneous high expression of both VvDTC2 and VvDTC3 in grape berry mesocarp close to the onset of ripening suggests that these carriers might be involved in the transport of malate into mitochondria.

Wheat is a major staple crop, and its grain yield is affected by heat stress. Such environmental constraint frequently occurs in the main Portuguese wheat producing regions. The aim of this work was to evaluate the impact of high temperatures after anthesis on gas exchanges, chlorophyll a fluorescence, membrane integrity and yield in nine Portuguese old bread wheat varieties. Photosynthetic rate (Pn) reductions occurred in Gentil Rosso, Grécia and Nabã o and may result from inactivation of PSII activity, as indicated by decreases in photochemical efficiency under light (Fv'/Fm') and in quantum yield of electron transport ( e ). Results denoted an enhancement/maintenance of photosynthetic ability under heat, expressed by stable stomatal conductance (gs) and higher water use efficiency (WUE) in MEQ and Restauraçã o, increased Pn in MEB and Restauraçã o, and Pn stability in Ruivo. Reduced membrane damage (lower leakage) in Ruivo and MEQ suggested a higher protoplasmic tolerance to heat in these varieties. Control plants of MEQ also presented the highest lipid amount and the less unsaturated membrane lipids (low double bond index), and these traits were unaffected by heat. Ruivo denoted a stimulation of lipid biosynthesis which could have positive implications on thermal tolerance. Increased Pn and WUE, stable gs and abundant lipids in control plants (MEQ, T94, MEB, Restauraçã o) corresponded to kernel yield increases under heat. Physiological traits are expected to contribute to Portuguese wheat breeding programs towards high temperature tolerance.

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Ceratonia siliqua and some species of Prosopis (Fabaceae family) are commonly known as carob trees. The flours obtained from their pods are used in the food industry, as cocoa substitute in the confectionery and also used in beverages and mixed with products derived from cereals. The aim of this study was to compare and characterize the physical and chemical properties, specially the antioxidant activities, of the two commercial carob flours. Commercial Prosopis spp. (mainly from P. alba) flour exhibited high content of protein, starch and fat, while commercial flour from C. siliqua had a lower content of these compounds, but higher antioxidant activity. By nuclear magnetic resonance (NMR) the aqueous extracts of the two carob flours were analysed and concluded that they had similar content of sucrose, but C. siliqua had more monosaccharides and pinitol. This important cyclitol has beneficial physiological effects, improving the glycaemic level and, thus, having a great potential in the food industry. We conclude that the commercial flour of C. siliqua has a better nutritional potential than that of Prosopis spp., owing to dietary fiber, total phenols, pinitol and antioxidant activity. Our results corroborate the nutritional benefits of the commercial supplements already available for healthy food formulations.