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Environmental stress triggered by climate change can alter the plant's metabolite profile, which affects its physiology and performance. This is particularly important in medicinal species because their economic value depends on the richness of their phytocompounds. We aimed to characterize how water deficit modulated the medicinal species Melia azedarach's lipophilic profile and antioxidant status. Young plants were exposed to water deficit for 20 days, and lipophilic metabolite profile and the antioxidant capacity were evaluated. Leaves of M. azedarach are rich in important fatty acids and oleamide. Water deficit increased the radical scavenging capacity, total phenol, flavonoids, and catechol pools, and the accumulation of β-sitosterol, myo-inositol, succinic acid, sucrose, d-glucose and derivatives, d-psicofuranose, d-(+)-fructofuranose, and the fatty acids stearic, α-linolenic, linoleic and palmitic acids. These responses are relevant to protecting the plant against climate change-related stress and also increase the nutritional and antioxidant quality of M. azedarach leaves. [ABSTRACT FROM AUTHOR]

Highlights • Most abundant lipophilic and phenolic compounds in olive leaves are highlighted. • UV-B radiation and heat differently modulate the lipophilic and phenolic content of olive leaves. • Flavonoids, secoiridoids and monoterpenes are highly responsive to heat and UV-B radiation. • Hydroxycinnamic acids, triterpenes, sterols and fatty acids are little affected by UV-B and heat. Abstract Olea europaea L. is the basis of the olive oil chain value. Olive by-products remain economically underexplored despite their richness in polyphenols and fatty acids. Heat waves and raised UV-B radiation episodes (that increasingly affect Mediterranean orchards) may influence these compounds. Herein we characterize the most relevant leaf lipophilic and phenolic compounds of an important Portuguese cultivar Cobrançosa, immediately and 30 days after exposure to high UV-B radiation or heat shock (HS). Plants were exposed to either UV-B (12 kJ m−2 d-1) or HS (40 °C for 2 h) for two consecutive days. Hydroxycinnamic acids, triterpenes, sterols and fatty acids are less influenced by UV-B and HS, while the amounts of flavonoids, secoiridoids and monoterpenes increased. In particular, after both treatments, quercetin-3- O -glucoside levels increased in leaves, and UV-B stimulated oleuropein levels. HS reduced the amounts of verbascoside, oleuropein and luteolin-7- O -glucoside, while UV-B only decrease apigenin-7- O -rutinoside levels. Thirty days after UV-B and HS relief, these compounds showed different profiles. Whereas UV-B recovering plants showed increased amounts of thymol-β- d -glucopyranoside, in HS recovering plants, the increase was more relevant for oleuropein, chrysoeriol-7- O -glucoside and luteolin-7- O -glucoside. Data evidence that Cobrançosa leaves are particularly rich in luteolin-7- O -glucoside, oleuropein, and oleic and palmitic acids, and that their levels may be stimulated by climate-change related conditions, contributing to the economical valorisation of leaves. [ABSTRACT FROM AUTHOR]

Abstract The interaction of lead (Pb) with plant hormonal balance and oxidative stress remains under discussion. To evaluate how Pb induces oxidative stress, and modulates the antioxidant enzymes and the phytohormones pool, four-week old Pisum sativum plants were exposed during 28 days to 10, 100 and 500 mg kg−1 Pb in soil. In comparison to leaves, roots showed higher Pb accumulation, oxidative damages and changes in phytohormone pools. Contrarily to leaves, where glutathione reductase (GR) and ascorbate peroxidase (APX) activities were more stimulated than catalase (CAT) and superoxide dismutase (SOD), roots showed a stimulation of SOD, GR and APX in all doses, and of CAT in the highest dose. While protein oxidation occurred in roots even at lower Pb-doses, lipid peroxidation and membrane permeability also occurred but at 500 mg kg−1 and in both organs, accompanied by increases of H 2 O 2. Jasmonic acid (JA) responded in both organs even at lowest Pb-doses, while salicylic acid (SA) and abscisic acid (ABA, only in leaves), increased particularly at the concentration of 500 mg Pb kg−1. In conclusion, and compared with leaves, roots showed oxidative damage even at 10 mg Pb Kg−1, being proteins a first oxidative-target, although there is a stimulation of the antioxidant enzymes. Also, JA is mobilized prior to oxidative stress changes are detected, and may play a protective role (activating antioxidant enzymes), while the mobilization of SA is particularly relevant in cells expressing oxidative damage. Other hormones, like indolacetic acid and ABA may have a low protective role against Pb toxicity. Graphical abstract Image 1 Highlights • Oxidative stress and hormonal changes in response to Pb are more evident in roots. • JA responds to low/moderate Pb-doses, while SA and ABA respond to higher doses. • JA correlates with antioxidant enzymes, having a preventive role against ROS damage. • SA antioxidant role is more relevant when plants show some oxidative damages. [ABSTRACT FROM AUTHOR]

Titanium dioxide nanoparticles (TiO2-NP) are increasingly being proposed for nanoagriculture but their effect on photosynthesis is limited and contradictory, mostly regarding putative chronical effects associated to the exposure to the commercial P25 formulation (anatase:rutile). This research aims at evaluating how chronical exposure to P25-NP affect photosynthetic processes in Triticum aestivum. Wheat plants were exposed (from the germination stage) to 0, 5, 50, and 150 mg L−1 P25-NP for 20 days. P25-NP impaired both light-dependent and -independent phases of photosynthesis, decreased chlorophyll a content, maximal and effective efficiency of PSII, net photosynthetic rate, transpiration rate, stomatal conductance, intercellular CO2 concentration, and starch content. On the other hand, no effects were observed in photochemical and in non-photochemical quenching values, on total soluble sugar (TSS) content or in RuBisCO activity. Our results support that the induced decay in chlorophyll a content compromised the electron transport through PSII and that stomatal limitations impaired CO2 assimilation. The decline of starch content seems to be a consequence of its degradation as a mechanism to maintain the TSS levels. Consequently, we propose that photosynthetic related endpoints are sensitive and valuable biomarkers to assess TiO2-NP toxicity. [ABSTRACT FROM AUTHOR]

Economically important forest species as Eucalyptus globulus face risks associated with climate changes, whose immediate and long-term damages are yet to account. The aim of this study was to decipher the impacts of UV-B radiation on the physiological performance and metabolome profile of leaves of Eucalyptus juvenile plants. For that, three-month-old plants were treated for two days to a total effective radiation of 12 kJ m −2 . One and 11 d after treatment the samples were collected for photosynthetic analyses. UV-B did not affect the photochemical efficiency or gas exchange, but the total soluble sugars (TSS), starch levels and pigment contents were changed. Changes in TSS and pigment contents persisted in time after the end of exposure. The profile of volatile metabolites (1 and 11 days after stress removal) was analyzed by HS-SPME/GC-IT-MS, and showed abundance of monoterpenes, sesquiterpenes and aldehydes. One day after the stress removal, an increase of aldehydes was observed and a decrease of some monoterpenes and sesquiterpenes. Eleven days after stress removal, some monoterpenes and sesquiterpenes decreased to values closer to those of control. The absence of mortality, and the minor effects observed in photosynthesis suggest a high tolerance profile of this species to the UV-B dose used, which may be justified by changes at the level of primary metabolism (involving sugars) and secondary (e.g. terpenes) observed in response to UV's. The correlations of these changes with potential functional adaptations are discussed here. [ABSTRACT FROM AUTHOR]

The continued use of synthetic herbicides to control weeds leads to environmental pollution and health issues. Consequently, chemical formulations have been increasingly banned. However, sustainable solutions are lacking in the market. Alternatively, valorisation of phytotoxic waste to reduce the herbicides use promotes sustainability, meeting circular economy. We aimed at assessing the herbicidal potential of aqueous extracts of waste from the management of invasive plants (Acacia dealbata bark, Oxalis pes-caprae biomass) and agri-food (spent coffee grounds) on common urban weeds (Achillea ageratum, Conyza canadensis and Dittrichia viscosa) in Portugal. In vitro (paper and soil) and pot assays (soil) were conducted to test the pre-emergence (germination and seedlings) and post-emergence (well-stablished plants) effect of waste extracts on these weeds. Extracts reduced pre-emergence performance of weeds, but marginally affected post-emergence parameters. Germination was inhibited up to 83% by O. pes-caprae in A. ageratum, up to 88% and 87% by A. dealbata and O. pes-caprae in C. canadensis, and up to 70% by concentration in D. viscosa. A. dealbata and O. pes-caprae extracts also drastically reduced radicle length (30% and 55% in A. ageratum, 77% and 81% in C. canadensis, 90% and 92% in D. viscosa, respectively). However, soil neutralized the inhibitory pre-emergence effect. The main findings highlight that the use of A. dealbata and O. pes-caprae extracts as bioherbicides may require an additional synthetic herbicides application, as extracts alone cannot fully control urban weeds in areas without soil. Combining bioherbicides and commercial formulations still reduces the application of toxic chemicals, promoting sustainability. [ABSTRACT FROM AUTHOR]

Extreme climate change events, such as long periods of drought and heat waves, are predicted to increase throughout this century. Pinus species are important economic resources. However, it remains unknown the vulnerability of most species to climate change-related stresses. We aimed to compare the performance reconfiguration of two resin/timber important species [ Pinus elliottii var. elliottii (PE) and the hybrid Pinus elliottii var. elliottii × Pinus caribaea var. hondurensis (PE × PCH)] to face combined stress of drought+heat. Young PE and PE × PCH plants were grown at optimal conditions, then exposed to water deficit for 5 days, and in the last day of water deficit, plants were additionally exposed to a heat shock. The physiological responses, antioxidant capacity and oxidative stress were evaluated immediately and 5 days (recovery) after drought+heat treatment. Under control conditions, the hybrid displayed higher photosynthetic and biochemical performance (e.g. higher net CO 2 assimilation rate, transpiration rate, photosynthetic pigments and anthocyanins levels, carbohydrates and antioxidant enzyme activities). Immediately after the drought+heat episode, plant water status decreased in both species, as well as the PSII photosynthetic parameters (Ф PSII and F v '/F m '), while non-photochemical quenching increased. However, the gas-exchange parameters of PE and the hybrid responded differently to the combined stress. The hybrid suffered a stronger reduction on the net CO 2 assimilation rate and transpiration rate, and presented higher levels of lipid peroxidation, but with no cell membrane permeability injuries. Principal component analysis supports that the different profile of both species is possibly associated to the stronger antioxidant capacity of PE under stress conditions. Moreover, these differences were still observed during recovery and photosynthesis was re-established totally only in PE. The hybrid clearly demonstrated less ability to restore the gas-exchange in the same period, possibly due to stomata re-opening limitations. The low net CO 2 assimilation rates in the hybrid after stress relief could also result in the necessity to use the starch reserves to maintain TSS pools available for stress recovery. We conclude that the hybrid perform better under control conditions, and the PE seems better prepared to cope with the predictable global climate change scenarios forecast for the next decades. The hybrid is more affected by drought+heat, but is able to keep a photosynthetic performance close to the PE under stress, although less efficient during recovery. • The hybrid has a higher physiological performance under optimal growth conditions. • The PE is better prepared to cope with drought and heat episodes. • The hybrid has less ability to recovery the physiological performance after stress. [ABSTRACT FROM AUTHOR]

Highlights: [•] ABA pretreatment effects in U. minor growth and antioxidant capacity were analyzed. [•] ABA reduces water loss and increases plant growth under WW and WS conditions. [•] ABA increases WS tolerance by prevention of oxidative membrane damages. [•] ABA delays S-phase and increases FPCV. [•] ABA pretreatment could be a strategy to decrease the negative effect of WS. [ABSTRACT FROM AUTHOR]

Abstract: Candidate species for reforestation of areas prone to drought must combine water stress (WS) tolerance and economic or medicinal interest. Melia azedarach produces high quality timber and has insecticidal and medicinal properties. However, the impact of WS on M. azedarach has not yet been studied. Two-month old M. azedarach plants were exposed to WS during 20 days. After this period, plant's growth, water potential, photosynthetic performance and antioxidant capacity were evaluated. WS did not affect plants' growth, but induced stomatal closure, reduced net CO2 assimilation rate (A) and the intercellular CO2 availability in mesophyll (C i). WS also reduced the photosynthetic efficiency of PSII but not the pigment levels. WS up-regulated the antioxidant enzymes and stimulated the production of antioxidant metabolites, preventing lipid peroxidation. Therefore, despite some repression of photosynthetic parameters by WS, they did not compromise plant growth, and plants increased their antioxidant capacity. Our data demonstrate that M. azedarach juvenile plants have the potential to acclimate to water shortage conditions, opening new perspectives to the use of this species in reforestation/afforestation programs of drought prone areas. [Copyright &y& Elsevier]

In the last decades, the use of fungicides in agriculture for fungi diseases control has become crucial. Fungicide research has produced a diverse range of products with novel modes of action.However, the extensive use of these compounds in the agriculture system raises public concern because of the harmful potential of such substances in the environment and human health. Moreover, the phytotoxic effects of some fungicides are already recognized but little is known about the impact of these compounds on the photosynthetic apparatus. This paper presents a comprehensive overview of the literature considering different classes of fungicides and their effects on plant physiology, with particular emphasis on photosynthesis. [ABSTRACT FROM AUTHOR]

In recent years, more attention has been paid to natural sources of antioxidants. Flavonoids are natural substances synthesized in several parts of plants that exhibit a high antioxidant capacity. They are a large family, presenting several classes based on their basic structure. Flavonoids have the ability to control the accumulation of reactive oxygen species (ROS) via scavenger ROS when they are formed. Therefore, these antioxidant compounds have an important role in plant stress tolerance and a high relevance in human health, mainly due to their anti-inflammatory and antimicrobial properties. In addition, flavonoids have several applications in the food industry as preservatives, pigments, and antioxidants, as well as in other industries such as cosmetics and pharmaceuticals. However, flavonoids application for industrial purposes implies extraction processes with high purity and quality. Several methodologies have been developed aimed at increasing flavonoid extraction yield and being environmentally friendly. This review presents the most abundant natural flavonoids, their structure and chemical characteristics, extraction methods, and biological activity. [ABSTRACT FROM AUTHOR]

The frequency of combined stress events is increasing due to climate change and represents a new threat to olive (Olea europaea) culture. How olive plants modulate their profile of metabolites under multiple stressing agents remains to unveil, although several metabolites affect plants' resilience, and olive production and quality. Young olive plants were exposed to a water deficit (WD) for 30 days and then exposed to a shock of heat and high UVB-radiation (WDHS+UVB treatment) for 2 days. Then, plants were re-watered and grown under optimal conditions (recovery) for 30 days. Leaves were collected after stress and recovery, analysed by liquid and gas chromatography, and the lipophilic and phenolic profiles were characterized. Except for the oleuropein derivatives, the qualitative metabolite profile was similar during stress and recovery. Metabolite increases or decreases in response to stress were stronger when WD was followed by WDHS+UVB treatment. Phenolic compounds (luteolin-7- O -glucoside, quercetin-3- O -rutinoside, apigenin-7- O -glucoside, chrysoeriol-7- O -glucoside, kaempferol derivatives, oleuropein, and lucidumoside C) were the most involved after WD and WDHS+UVB, possibly acting as reactive oxygen species (ROS) scavengers. Lipophilic compounds were more relevant during the recovery period. The catabolism of fatty acids and carbohydrates may provide the necessary energy for plant performance reestablishment, and sterols, long-chain alkanes, and terpenes metabolic pathways may be shifted for the production of compounds with a more important stress protection role. This work highlights for the first time that tolerance mechanisms activated by WD in olive plants are related to metabolite changes, that are adjusted when other stressors are overlapped (WDHS+UVB), and also help the plants recover. This metabolites' plasticity represents an essential contribution to understanding how dry-farming olive orchards may deal with drought combined with high UV-B or heat. [Display omitted] • WD and WDHS+UVB activate the same metabolite responses. • WDHS+UVB induce a stronger metabolite quantity change. • Polyphenols are the most involved to counteract the stress negative effects. • Lipophilic metabolites are more involved in physiological reestablishment after stress. [ABSTRACT FROM AUTHOR]

Iron-magnetic nanoparticles (Fe-NMPs) are widely used in environmental remediation, while porphyrin-based hybrid materials anchored to silica-coated Fe 3 O 4 -nanoparticles (Fe 3 O 4 -NPs) have been used for water disinfection purposes. To assess their safety on plants, especially concerning potential environmental release, it was investigated for the first time, the impact on plants of a silica-coated Fe 3 O 4 -NPs bearing a porphyrinic formulation (FORM) - FORM@NMP. Additionally, FORM alone and the magnetic nanoparticles without FORM anchored (NH 2 @NMP) were used for comparison. Wheat (Triticum aestivum L.) was chosen as a model species and was subjected to three environmentally relevant doses during germination and tiller development through root application. Morphological, physiological, and metabolic parameters were assessed. Despite a modest biomass decrease and alterations in membrane properties, no major impairments in germination or seedling development were observed. During tiller phase, both Fe 3 O 4 -NPs increased leaf length, and photosynthesis exhibited varied impacts: both Fe 3 O 4 -NPs and FORM alone increased pigments; only Fe 3 O 4 -NPs promoted gas exchange; all treatments improved the photochemical phase. Regarding oxidative stress, lipid peroxidation decreased in FORM and FORM@NMP, yet with increased O 2 -• in FORM@NMP; total flavonoids decreased in NH 2 @NMP and antioxidant enzymes declined across all materials. Phenolic profiling revealed a generalized trend towards a decrease in flavones. In conclusion, these nanoparticles can modulate wheat physiology/metabolism without apparently inducing phytotoxicity at low doses and during short-time exposure. Iron-magnetic nanoparticles are widely used in environmental remediation and fertilization, besides of new applications continuously being developed, making them emerging contaminants. Soil is a major sink for these nanoparticles and their fate and potential environmental risks in ecosystems must be addressed to achieve more sustainable environmental applications. Furthermore, as the reuse of treated wastewater for agricultural irrigation is being claimed, it is of major importance to disclose the impact on crops of the nanoparticles used for wastewater decontamination, such as those proposed in this work. [Display omitted] • FORM@NMP promoted gas exchange and Φ PSII , and down regulated the antioxidant response. • NH 2 @NMP increased pigment levels, gas exchange, and Φ PSII. • FORM impaired seedling biomass, increased pigments and Φ PSII , and decreased MDA. • Flavone levels showed a generalized trend do be down regulated. [ABSTRACT FROM AUTHOR]

The Mediterranean crop Olea europaea is often exposed to high UV-B irradiation conditions. To understand how this species modulates its enzymatic and non-enzymatic antioxidant system under high UV-B radiation, young O. europaea plants (cultivar "Galega Vulgar") were exposed, for five days, to UV-B radiation (6.5 kJ m−2 d−1 and 12.4 kJ m−2 d−1). Our data indicate that UV-doses slightly differ in the modulation of the antioxidant protective mechanisms. Particularly, superoxide dismutase (SOD), guaiacol peroxidase (GPox) and catalase (CAT) activities increased contributing to H 2 O 2 homeostasis, being more solicited by higher UV-B doses. Also, glutathione reductase (Gr) activity, ascorbate (AsA) and reduced glutathione (GSH) pools increased particularly under the highest dose, suggesting a higher mobilization of the antioxidant system in this dose. The leaf metabolites' profile of this cultivar was analysed by UHPLC-MS. Interestingly, high levels of verbascoside were found, followed by oleuropein and luteolin-7- O -glucoside. Both UV-B treatments affected mostly less abundant flavonoids (decreasing 4ʹ-methoxy luteolin and 4ʹ or 3ʹ-methoxy luteolin glucoside) and hydroxycinnamic acid derivatives (HCAds, increasing β-hydroxyverbascoside). These changes show not only different mobilization with the UV-intensity, but also reinforce for the first time the protective roles of these minor compounds against UV-B, as reactive oxygen species (ROS) scavengers and UV-B shields, in complement with other antioxidant systems (e.g. AsA/GSH cycle), particularly for high UV-B doses. Secoiridoids also standout in the response to both UV-B doses, with decreases of oleuropein and increases 2ʹʹ-methoxyoleuropein. Being oleuropein an abundant compound, data suggest that secoiridoids play a more important role than flavonoids and HCAds, in O. europaea protection against UV-B, possibly by acting as signalling molecules and ROS scavengers. This is the first report on the influence of UV-B radiation on the secoiridoid oleuropein, and provides a novel insight to the role of this compound in the O. europaea antioxidant defence mechanisms. Image 1 • Moderate and high UV-B doses activated similar antioxidant protective mechanisms. • High UV-B dose promote higher activation of the antioxidant enzymes and AsA/GSH. • Flavonoids, secoiridoids and HCAds respond similarly to 6.5 and 12.4 kJ m−2d−1 UV-B • UV-B treatments reduce some protective compounds level, such as oleuropein. [ABSTRACT FROM AUTHOR]

Climate change is increasing the frequency of heat waves accompanied by drought episodes. These challenges are increasing in the Mediterranean basin, where Olea europaea L. has an important ecological and economic role. Olive breeding programs have been focused on highly productive cultivars, while ancient cultivars may present higher tolerance to drought and heat resilience. Therefore, it is important to select traditional cultivars that may give reliable performances under the emerging climate change scenarios. In the present work, the differential physiological response of economically important traditional Portuguese olive cultivars, Cobrançosa, Cordovil de Castelo Branco (C.C. Branco), and Cordovil de Serpa (C. Serpa), to drought combined with heat are evaluated. Stress treatment had lowest impacts on water status in Cobrançosa. Also, this cultivar was less affected regarding pigments content, maximum and effective quantum yield of photosystem II (F v /F m and Φ PSII ) and exhibited higher ability to trigger an antioxidant response. C.C. Branco was the most sensitive cultivar in response to pigments (carotenoids), F v /F m and Φ PSII , and cell membrane stability. Principal component analysis suggested that Cobrançosa has high potential to withstand climate change events, particularly drought combined with heat episodes, followed by C. Serpa and C.C. Branco. [ABSTRACT FROM AUTHOR]

Abstract: The ability of crops to overcome Al toxicity varies among crop species and cultivars. Among the Triticeae genus, rye (Secale cereale) is considered the most Al-tolerant species. In the present work, two rye genotypes differing in Al tolerance (‘Riodeva’: Al-sensitive and ‘Donkowsky Zlote’: Al-tolerant) were exposed to 1.11 and 1.85 mM Al during three weeks. Growth, water status and photosynthesis related parameters were assessed. After three weeks of Al exposure, both genotypes presented similar decrease in leaf growth. Al-induced RWC decreased in both genotypes, but was more remarkable in ‘Riodeva’. Al toxicity induced a decrease in net photosynthetic rate only after three weeks of exposure. In ‘D. Zlote’, A decrease was accompanied by stomatal closure, Chl a content and q p reduction, but no alterations in RuBisCo or sFBPase activity were observed. In ‘Riodeva’ plants exposed to 1.11 mM Al, A decrease was accompanied by Ci /Ca increase whereas in plants exposed to 1.85 mM Al Ci /Ca was not affected. Nevertheless, for both conditions RuBisCo activity decreased. A decrease did not limited glucose accumulation in neither of the rye genotypes. This study revealed that Al-induced earlier damages in the ‘Riodeva’ genotype, but both genotypes showed long-term high susceptibility to Al. Furthermore, the photosynthetic parameters proved to be a good tool to monitor Al-sensitivity and long-term exposure showed to be crucial to evaluate Al-sensitivity. [Copyright &y& Elsevier]

In recent decades, atmospheric pollution led to a progressive reduction of the ozone layer with a consequent increase in UV-B radiation. Despite the high adaptation of olive trees to the Mediterranean environment, the progressive increase of UV-B radiation is a risk factor for olive tree cultivation. It is therefore necessary to understand how high levels of UV-B radiation affect olive plants and to identify olive varieties which are better adapted. In this study we analyzed two Italian olive varieties subjected to chronic UV-B stress. We focused on the effects of UV-B radiation on RubisCO, in terms of quantity, enzymatic activity and isoform composition. In addition, we also analyzed changes in the activity of antioxidant enzymes (SOD, CAT, GPox) to get a comprehensive picture of the antioxidant system. We also evaluated the effects of UV-B on the enzyme sucrose synthase. The overall damage at biochemical level was also assessed by analyzing changes in Hsp70, a protein triggered under stress conditions. The results of this work indicate that the varieties (Giarraffa and Olivastra Seggianese) differ significantly in the use of specific antioxidant defense systems, as well as in the activity and isoform composition of RubisCO. Combined with a different use of sucrose synthase, the overall picture shows that Giarraffa optimized the use of GPox and opted for a targeted choice of RubisCO isoforms, in addition to managing the content of sucrose synthase, thereby saving energy during critical stress points. [ABSTRACT FROM AUTHOR]

• TiO 2 -NP is toxic above 5 mg L−1, being wheat shoots more sensitive than roots. • Leaves triggered thiol and AsA metabolism to counteract TiO 2 -NP toxicity. • Roots preferred antioxidant route involves pre-existing antioxidant capacity. • The induced antioxidant mechanisms did not prevent cellular oxidation. • Biochemical and transcriptional gap responses suggest time-dependent adaptations. Nanoparticles (NP) bioactivity is under deep scrutiny. In this work, the antioxidant response to TiO 2 -NP in wheat (Triticum aestivum) was determined. For that, enzymatic and the non-enzymatic antioxidants were evaluated in plants exposed to the P25 anatase:rutile material composed of TiO 2 -NP and under environmentally realistic doses (0; 5; 50; 150 mg/L for 20 days). Shoot but not root growth was reduced. In leaves, thiol metabolism and ascorbate accumulation were the preferred route whereas in roots the pre-existing antioxidant capacity was preferentially utilized. Both leaves and roots showed increased glutathione reductase and dehydroascorbate reductase activities and decreased ascorbate peroxidase activity. Roots, nevertheless, presented higher enzymatic basal levels than leaves. On the other hand, when examining non-enzymatic antioxidants, the ratio of reduced-to-oxidized glutathione (GSH/GSSG) increased in leaves and decreased in roots. Exposed leaves also presented higher total ascorbate accumulation compared to roots. TiO 2 -NP exposure down regulated, with more prominence in roots, antioxidant enzyme genes encoding catalase, ascorbate peroxidase, monodehydroascorbate reductase and dehydroascorbate reductase. In leaves, superoxide dismutase gene expression was increased. All data pinpoint to TiO 2 -NP toxicity above 5 mg/L, with aerial parts being more susceptible, which draws concerns on the safety doses for the use of these NPs in agricultural practices. [ABSTRACT FROM AUTHOR]

Highlights • UV-A and UV-B can be used to modulate the tomato fruit quality. • UV-A supplementation increases the concentration of antioxidant compounds in fruits. • The UV-A doses tested here are more promising than UV-B. Abstract Solanum lycopersicum L. is among the healthiest fruits/vegetables due to its richness in bioactive compounds. However, its fruits from off-season (usually obtained in greenhouses that block UV-rays) have lower reputation than the ones of in-season/field productions. We hypothesise that moderate UV-A/UV-B irradiation during fruit development is able to improve its bioactive compounds and sensorial attributes, increasing its healthy properties. We supplemented for 30 days 'MicroTom' fruiting plants with two daily doses of UV-A (1 or 4 h) and UV-B (2 or 5 min). Irradiated plants showed higher ripening synchronization and produced more and smaller fruits. UV-A irradiation stimulated the fruit's antioxidant capacity, and the antiradical activity by the accumulation of phenolic compounds including the flavonoids. Only the UV-A1 h condition promoted the accumulation of ortho-diphenols in tomato fruits. Regarding the consumers' preference for aroma/taste, a consumers' panel test ranked the tomatoes as UV-A 1 h, UVA 4 h, Control, UV-B 5 min and UV-B 2 min. We conclude that the supplementation of UV-A during pre-harvest is particularly effective in increasing ripening synchronization and fruit's nutritional properties, potentially making these fruits more appealing to consumers. [ABSTRACT FROM AUTHOR]

Climate change scenarios increase the frequency of combined episodes of drought, heat and high UV radiation, particularly in the Mediterranean region where dryland farming of olive (Olea europaea L.) orchards remains a common practice. Nonirrigated olive plants (drought treatment) were subjected to an episode of heat plus UV-B radiation shock (DH+UV-B treatment) for 2 days. After the treatments, plants were allowed to grow under irrigated conditions (recovery). Compared with irrigated plants, drought treatment induced lower relative water content but this status was not aggravated when DH+UV-B shock was applied. Additionally, the effective quantum yield of PSII was similar in the drought-stressed and DH+UV-B treatments. Interestingly, the DH+UV-B treatment produced higher photosynthetic pigment contents than drought-stressed plants. Concerning oxidative status, the DH+UV-B treatment induced similar lipid peroxidation levels and only cell membrane permeability was higher than in drought-stressed plants. On other hand, drought-stressed plants showed higher levels of anthocyanins and proline. Our data suggest that plants grown under dryland conditions modulated some tolerance mechanisms that may prevent cumulative damages by other stressors. Moreover, drought-stressed and DH+UV-B plants were able to recover their physiological performance in a similar way. These data represent an important contribution to understanding how dryland -grown olive plants will cope with climate change. Climate changes are increasing the frequency of crop stress events, particularly in the Mediterranean region where dryland olive farming remains a sustainable practice. We aimed to evaluate how olive plants under irrigated versus dryland farming regimes respond to heat plus high UV-B, and recover. The results suggest that plants pre-exposed to drought can modulate tolerance mechanisms towards coping with further multiple stress episodes and recovery. [ABSTRACT FROM AUTHOR]

Chromium (Cr) contamination in arable soils and irrigating water remains a priority, particularly due to the challenges posed to crop production and food safety. Long-term Cr(VI) effects remain less addressed than short-term ones, particularly regarding organ-specific genotoxic profiles. Here we used the crop Lactuca sativa growing in a protected horticultural system and irrigated for 21 days with Cr(VI) (up to 200 mg/L). Besides the oxidative stress, the genotoxicity was evaluated. Shoots and roots showed distinctive oxidative stress status and genotoxic effects, in a dose-dependent manner. While 50 mg/L stimulated antioxidant activities and no major genotoxic effects were found, plants exposed to ≥150 showed an increase of oxidative disorders, together with cytostatic and DNA damage effects, and some mitotic impairment. Leaves showed less oxidative signs at 50 mg/L, while at 150/200 mg/L the antioxidant battery was stimulated. In Cr treated plants, the highest dose increased the DNA damage, reinforcing the idea that DNA breaks were related to mitotic disorders in higher doses. In conclusion, long-term exposure data show a highly responsive root, with a quadratic response meaning higher defenses at lower Cr doses, and higher oxidative and DNA damage and cytostatic effect at a higher dose. [ABSTRACT FROM AUTHOR]

Clonal breeding programs of the highly important interspecific hybrid Pinus elliottii var. elliottii and Pinus caribaea var. hondurensis require the establishment of robust cryopreservation protocols, with no genetic variability. Embryonal masses of this hybrid were successfully cryopreserved by a fast slow-freezing method. The protocol was optimized by testing the effects of dimethyl sulfoxide (DMSO) based cryoprotectant solutions, sugar cryoprotectants (e.g. sucrose or maltose, 0.4 M) and different times of pretreatments and pre-cooling storage. The addition of DMSO in a mixture of polyethylene glycol (PEG) 4000 and sucrose (PSD solution), instead of DMSO alone, was beneficial for recovery of cryopreserved cultures. This parameter, together with the time of pre-cooling storage (before plunging in liquid nitrogen), were the factors that most influenced the survival and regrowth rates of embryonal masses. A pretreatment combination of sucrose (0.4 M) and 5% PSD followed by a pre-cooling storage of 24 h allowed the cryopreservation and regrowth of embryogenic cell lines without major genetic variations (DNA-ploidy) or loss of embryogenic potential. Eight of the nine tested embryogenic cell lines survived to the cryopreservation procedures, however the genotype and treatment conditions clearly influenced the response. Somatic embryos maturation and conversion from recovered embryonal masses (EMs) took place according to our standard somatic embryogenesis protocol for Pinus , using modified Litvai (mLV) medium. This is the first report for this hybrid, and the proposed protocol is fast, robust, providing high rates of recovery and working with several genotypes. This protocol’s suitability for industrial breeding programmes was also confirmed by allowing the regeneration of plants with no apparent variability from cryopreserved embryonal masses. [ABSTRACT FROM AUTHOR]

Pinus elliottii var. elliottii is a pine species with enormous economic value particularly for timber and resin industries, and is subject of high pressure for genetic improvement and cloning elite genotypes. We have recently developed a robust micropropagation protocol for this species. Plantlets performance needs to be evaluated to validate this protocol for further mass propagation. Micropropagated plantlets and seed-derived plants with similar age and shoot length were compared regarding photosynthesis, carbohydrates and pigments content, water status, DNA content and cell cycle dynamics. Micropropagated plantlets had an overall physiological performance similar to seed-derived plants. In particular, except for the transpiration rate ( E ), CO 2 assimilation rate ( A ) and total soluble sugars (TSS) content, no major differences between plantlets and seedlings in terms of relative water content (RWC), chlorophyll a fluorescence and pigments content were found. Genetic fidelity analyses support that the micropropagation protocol neither induce DNA content changes nor alterations in cell cycle dynamics. [ABSTRACT FROM AUTHOR]

Climatic change challenges are predicted to increase combined episodes of drought, heat and higher UVB-radiation, which will impact crops/plants production. Moringa oleifera is a major source of food/economy in underdeveloped regions, and its tolerance to high UVB radiation (UVB) and water deficit (WD) remains unclear. We exposed two-month old plants to: a) WD for 4 days; b) UVB radiation for 3 days (26.3 kJ m − 2 ); c) WD + UVB in combination for 4 days (the UVB stress was imposed at the 2nd day of WD). One and ten days after the end of stresses the following parameters were measured: plant growth, water-status, chlorophyll a fluorescence, leaf gas-exchange, pigments, carbohydrates, cell-membrane-stability, phenols, malondialdehyde content and antioxidant capacity (including antioxidant enzymes). Stress exposure did not affect plant water status. One day after the end of the stresses, net CO 2 assimilation rate dropped in all treatments, but after 10 days an overall recovery was observed, except in plants exposed to UVB treatment. The plants exposed to UVB showed, in general, more severe effects, increasing pigment content and MDA, while no changes were observed in the total antioxidant capacity (after 1 day). Our data suggest that young M. oleifera plants present some tolerance to WD or UVB radiation and that the combination of the two stresses led to lower stressful responses than the UV stress imposition alone (photosynthesis, pigments, starch and antioxidant capacity). The lower outcome shown in the combined stresses suggest that this species is able to cope multiple stresses, and that a previous acclimation (possibly activating the antioxidant capacity) to one of the stresses may play an important role in this tolerance. [ABSTRACT FROM AUTHOR]

Trees necessarily experience changes in temperature, requiring efficient short-term strategies that become crucial in environmental change adaptability. DNA methylation and histone posttranslational modifications have been shown to play a key role in both epigenetic control and plant functional status under stress by controlling the functional state of chromatin and gene expression. Cork oak (Quercus suber L.) is a key stone of the Mediterranean region, growing at temperatures of 45°C. This species was subjected to a cumulative temperature increase from 25°C to 55°C under laboratory conditions in order to test the hypothesis that epigenetic code is related to heat stress tolerance. Electrolyte leakage increased after 35°C, but all plants survived to 55°C. DNA methylation and acetylated histone H3 (AcH3) levels were monitored by HPCE (high performance capillary electrophoresis), MS-RAPD (methylation-sensitive random-amplified polymorphic DNA) and Protein Gel Blot analysis and the spatial distribution of the modifications was assessed using a confocal microscope. DNA methylation analysed by HPCE revealed an increase at 55°C, while MS-RAPD results pointed to dynamic methylation-demethylation patterns over stress. Protein Gel Blot showed the abundance index of AcH3 decreasing from 25°C to 45°C. The immunohistochemical detection of 5-mC (5-methyl-2'-deoxycytidine) and AcH3 came upon the previous results. These results indicate that epigenetic mechanisms such as DNA methylation and histone H3 acetylation have opposite and particular dynamics that can be crucial for the stepwise establishment of this species into such high stress (55°C), allowing its acclimation and survival. This is the first report that assesses epigenetic regulation in order to investigate heat tolerance in forest trees. [ABSTRACT FROM AUTHOR]

Abstract: In order to comprehensively characterize the effects of Cr (VI) on the photosynthetic performance of Pisum sativum, plants irrigated with Cr solutions (ranging from 20 to 2000 mg l−1) were evaluated using the following classical endpoints: gas exchange parameters, chlorophyll a (Chl a) fluorescence, leaf pigments, Rubisco activity, soluble sugars and starch content. Flow cytometry (FCM) was applied in an innovative approach to evaluate the morphological and fluorescence emission status of chloroplasts from plants exposed to Cr (VI). The parameters related to gas exchange, net CO2 assimilation rate (A) and Rubisco activity were severally affected by Cr exposure, in some cases even at the lowest dosage used. While all biomarkers used to measure Chl a fluorescence indicated a decrease in fluorescence at the maximum dosage, pigment contents significantly increased in response to Cr (VI). The morphology of chloroplasts also was altered by Cr (VI) exposure, as a volume decrease was observed. Soluble sugars and starch showed an overall tendency to increase in Cr (VI) exposed plants, but sucrose and glucose decreased highly when exposed to 2000 mg l−1. In conclusion, our results indicate that Cr (VI) affects photosynthesis at several levels, but the most Cr (VI)-sensitive endpoints were chloroplast morphology and biochemical processes; only at higher dosages the photochemical efficiency is compromised. [Copyright &y& Elsevier]

• Cobrançosa olives are richer in organic acids, esters and carbohydrates. • C.Serpa olives present higher levels of phenolic compounds. • Stress modulates olives' phenolic/lipophilic contents in a cultivar-dependent way. • C.Serpa olives have higher stress susceptibility than Cobrançosa and C.C.Branco. • Olives can be enriched in bioactive compounds in response to environmental stresses. The awareness of the functional and nutraceutical properties of olives and olive oil bioactive constituents contributed to oliviculture recent increase. Olives' metabolism and nutritional quality are determined by how the olive-tree is coping to climate change-related episodes, which increasingly occur in the Mediterranean. We characterize the most relevant lipophilic and phenolic compounds of olives from Olea europaea cultivars [Cobrançosa, Cordovil de Castelo Branco and Cordovil de Serpa (C.Serpa)] exposed to drought + heat. Olives from the three cultivars presented a similar qualitative profile but differed in their relative richness. Cobrançosa olives are richer in organic acids, esters and carbohydrates, while C.Serpa olives have higher levels of phenolic compounds, particularly under control conditions. Drought + heat changed the quantitative profile of olives, in a way dependent on the cultivar, and C.Serpa olives showed the highest stress susceptibility. Climate change-related conditions stimulate the accumulation of relevant bioactive compounds in olives, contributing to increasing its nutritional value. [ABSTRACT FROM AUTHOR]