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The predicted accentuation of drought events highlights the importance of optimize plants capacity to tolerate drought, but also the capacity to recovery from it, especially in species, as olive tree (Olea europaea L.), that grows in particularly susceptible regions. Three different concentrations (10, 100 and 1000 μM) of salicylic acid (SA), a stress signaling phytohormone, was sprayed on 3-year-old potted olive trees subjected to three successive drought and rewatering events. Trees responses to SA application are concentration dependent, being 100 μM the most effective concentration to improve drought tolerance and recovery capacity. During drought events, this effectiveness was achieved by osmolytes accumulation, leaf water status maintenance, reduced photosynthetic systems drought-associated damages, and by optimizing shoot/root ratio. The better plant fitness during drought allowed a fast recovery of the physiological functions upon rewatering and reduced the necessity to invest in extra repair damages, allowing the regrowth. The intense abscisic acid (ABA) signal close to upper epidermis in stressed controls suggests a “memory” of the worst water status displayed by those plants. SA attenuated the limitation of total biomass accumulation imposed by drought, mainly in root system, increased water use efficiency and lead to a higher intense signal of indoleacetic acid (IAA) in leaves during recovery period. In summary, in a suitable concentration, SA demonstrate to be a promising tool to increase drought adaptability of olive trees.

Nut production by the European sweet chestnut (Castanea sativa Mill.) in grafted orchards is under threat of increased drought stress associated with current global warming. To explore whether drought tolerance in C. sativa could be improved using drought tolerant scions and rootstocks, trees from humid (H) and xeric (X) populations in Spain were used to generate intra-family (H/H and X/X) and reciprocal inter-location (X/H and H/X) grafts. We studied the effects of the (i) scion, (ii) rootstock and (iii) the grafting itself as a wounding stress on the vegetative budbreak, secondary growth and drought tolerance of C. sativa trees. Drought tolerance was assessed by measuring leaf gas exchange, chlorophyll fluorescence, water status and leaf wilting two weeks after water deprivation. Hormone (ABA, SA, JA and JA-Ile) and proline quantification in tree leaves and fine roots were assessed, as well as tree and scion mortality. Rootstocks and scions of xeric origin induced earlier flushing and improved drought tolerance of scions and rootstocks of humid origin. Tree mortality after drought was 57 % lower in H/X than in H/H trees, and scion loss after drought was 47 % lower in H/X than in X/H trees. The ‘grafting’ (i.e., wounding) effect delayed vegetative budbreak and reduced secondary growth of trees but did not predispose trees to drought. We report for the first time differences in hormone and proline content in leaves and fine roots of chestnut trees of humid and xeric origins exposed to drought. The results suggest the use of scions and rootstocks from xeric areas to improve drought tolerance in chestnut.

Cork oak (Quercus suber L.) is a research priority in the Mediterranean area and because of cork oaks' distribution these stands are experiencing daily stress. Based on projections of intensifying climate change and considering the key role of exploring the recovery abilities, cork oak seedlings were subjected to a cumulative temperature increase from 25 degrees C to 55 degrees C and subsequent recovery. CO2 assimilation rate, chlorophyll fluorescence, anthocyanins, proline and lipid peroxidation were used to evaluate plant performance, while the relative abundance of seven genes encoding for proteins of cork oak with a putative role in thermal/stress regulation (POX1, POX2, HSP10.4, HSP17a.22, CHS, MTL and RBC) was analyzed by qPCR (quantitative Polymerase Chain Reaction). A temperature change to 35 degrees C showed abundance alterations in the tested genes; at 45 degrees C, the molecular changes were associated with an antioxidant response, possibly modulated by anthocyanins. At 55 degrees C, HSP17a.22, MTL and proline accumulation were evident. After recovery, physiological balance was restored, whereas POX1, HSP10.4 and MTL abundances were suggested to be involved in increased thermotolerance. The data presented here are expected to pinpoint some pathways changes occurring during such stress and further recovery in this particular Mediterranean species. (C) 2013 Elsevier GmbH. All rights reserved.

The plums used to produce a traditional candied product, “Ameixa d’Elvas”, were obtained from two orchards, Vila Vicosa (VV) and Cano (CA). These orchards were selected because the fruits were behaving differently: (1) The day of harvesting for candying, established by the total soluble solids and titratable acidity, was one week earlier in VV; (2) VV yielded candied plums with good texture properties whereas CA gave poor processed fruits. In order to understand the origin of these differences, fruits from both orchards were harvested on the day established as the harvesting day for VV (day 1) and for CA (day 8). Comparable texture properties were obtained in firmness, rigidity and deformation work between the VV fresh plums harvested on day 1 and the CA plums harvested on day 8 but these were lower in CA when the flesh was analysed separately, in accordance with the activities of pectin methyl esterase (PME), polygalacturonase (PG) and cellulase (Cel). The increase of the intercellular area of parenchyma cells and the decrease in cell area caused by boiling, which resulted in a pronounced loss of textural properties, were partially recovered after the immersion of the fruits in sucrose syrup. The CA plums harvested on day 8 had a more pronounced degradation with boiling and lower recovery of cell shape, size and textural characteristics than had those of VV harvested on day 1. Upon candying, similar properties were observed for the fruits harvested on the same day: good candied products were observed for VV and CA fruits harvested on day 1 and poor candied products were observed for VV and CA fruits harvested on day 8. This work shows that the characteristics of the flesh of the fresh fruits are key parameters in defining the textural properties of the candied plum. The establishment of the harvesting moment for candying should take into account the changes that occur in the flesh of the plums during ripening.

The plums ( Prunus domestica L.) of a specific ‘Green Gage’ variety, “Rainha Claudia Verde”, are used to produce the candied product “Ameixa d’Elvas”. The candying process consists in boiling the intact plums in water and further immersion in sucrose syrup until 75 °Brix. Scanning electron microscopy of unprocessed plums revealed perfectly turgid parenchyma isodiametric cells with few intercellular spaces and the boiled plums showed a loss of intercellular adhesion of parenchyma cells and ruptures on the vascular strand structure. However, candied plums showed recovery of the turgidity and cell-to-cell adhesion of parenchyma cells. Texture analysis showed that the unprocessed plums had a fairly hard texture, improved by the presence of the skin. Firmness, rigidity, and deformation work had a sharp decrease upon boiling. However, after candying, an increase of firmness and deformation work was observed, also improved by the skin. Microstructure and texture recovery of the candying product suggests the formation of a jam-like structure in the middle lamella region promoted by the syrup. Nevertheless, cell adhesion recovery is limited by the extent of the disruption of the tissues during the boiling process. This is the first report concerning texture and microstructure changes of plums occurring during the candying process.

Different media were assayed for Olea europaea L. ssp. maderensis Lowe micropropagation. Shoot elongation and propagation was more efficient on DKW medium supplemented with 4.4 μM BA and 0.4 μM IBA. Higher branching was obtained on OM medium supplemented with 18.2 μM zeatin. Rooting was achieved at higher rates on half strength DKW medium supplemented with 20.7 μM IBA. Plants were acclimated to greenhouse and up to now no morphological changes were observed among the regenerated in vitro plants.

Future climate in the Mediterranean grapevine (Vitis vinifera L.) growing regions will be characterized by more severe summer conditions, with lower water availability, increased temperature and elevated solar irradiance, which may bring relevant changes in grapevine performance. Although grapevines have several survival strategies, the amounting evidence for significant climate change in the upcoming decades urges short-term adaptation measures to be taken. With this in mind, the potential protective role of 5% foliar kaolin (KL), a white and inert clay mineral, was examined in the Port Wine Region over a two year period (2012 and 2013). The results revealed that leaves treated with KL showed higher light reflectance, lower leaf temperature and greater water potential, namely at midday period. As a consequence, net photosynthetic rates increased, particularly due to a lowering of mesophyll limitations, which include lesser perturbations in PSII photochemistry processes. In fact, sprayed KL plants had higher accumulation of active PSII reaction centres (RC) and capture efficiency of excitation energy by open RC, maximum and effective quantum efficiency of PSII, and electron transport rate. Moreover, KL application reduces the oxidative damage on cell membranes by lipid peroxidation. Altogether, these results and the delays in leaf senescence of grapevines sprayed with KL inhibited scorching of clusters and, consequently, lead to a higher yield per plant. Thus, kaolin is a very promising and cost- effective compound to alleviate the negative effects of summer stress in Mediterranean grapevines. In addition, since KL is a natural product can be used in organic farming.