Mecanismos de tolerancia a estrés salino e hídrico en plantas endémicas, raras o amenazadas.

Tesis por compendio[ES] La sequía y la salinidad son los factores ambientales que más afectan a las plantas, aunque en general, las plantas mediterráneas están bien adaptadas a las condiciones adversas. Las previsiones estiman que debido al calentamiento global las condiciones ambientales se volverán más estresantes, especialmente en las zonas semi-áridas y áridas como muchas áreas de la Península Ibérica. Estas condiciones pueden afectar a la presencia de muchas especies silvestres, en especial, de las que ya de por si están amenazadas, son raras o endémicas. Tanto la sequía como el estrés salino provocan la activación de una serie de mecanismos de defensa o respuesta de las plantas, que incluyen entre otros, el control del transporte iónico, la acumulación de solutos compatibles u osmolitos, y la activación de sistemas antioxidantes. Para contribuir a la conservación y/o reintroducción de las especies de interés en hábitats prioritarios se ha realizado un estudio multidisciplinar abarcando los parámetros que pueden afectar sus poblaciones, como el clima, el suelo, y la vegetación acompañante, junto a estudios comparativos sobre las respuestas a la sequía y a la salinidad. Para entender mejor los mecanismos de tolerancia se han incluido en el estudio además de los taxones de interés conservacionista, especies relacionadas genéticamente con diferentes niveles de tolerancia. El estudio presenta dos objetivos principales: i) establecer la tolerancia relativa al estrés hídrico y salino de las especies en base a su distribución en la naturaleza y en los análisis realizados en campo y, en función de la inhibición relativa de su crecimiento bajo condiciones provocadas de estrés; y, ii) evaluar los cambios bioquímicos inducidos por el estrés analizando diferentes mecanismos de respuesta (inhibición de la fotosíntesis, transporte iónico, acumulación de osmolitos, mecanismos antioxidantes).[CA] La sequera i la salinitat són els factors ambientals que més afecten les plantes, encara que en general, les plantes mediterrànies estan ben adaptades a les condicions adverses. Les previsions estimen que a causa del calfament global les condicions ambientals es tornaran més estressants, especialment en les zones semi-àrides i àrides com moltes àrees de la Península Ibèrica. Aquestes condicions poden afectar la presència de moltes espècies silvestres, especialment, de les que ja de per si estan amenaçades, són rares o endèmiques. Tant la sequera com l'estrès salí provoquen l'activació d'una sèrie de mecanismes de defensa o resposta de les plantes, que inclouen entre altres, el control del transport iònic, l'acumulació de soluts compatibles u osmolits, i l'activació de sistemes antioxidants. Per a contribuir a la conservació i/o reintroducció de les espècies d'interès en hàbitats prioritaris s'ha realitzat un estudi multidisciplinari abastant els paràmetres que poden afectar les seues poblacions, com el clima, el sòl, i la vegetació acompanyant, al costat d'estudis comparatius sobre les respostes a la sequera i a la salinitat. Per a entendre millor els mecanismes de tolerància s'han inclòs en l'estudi a més dels tàxons d'interès conservacionista, espècies relacionades genèticament amb diferents nivells de tolerància. L'estudi presenta dos objectius principals: i) establir la tolerància relativa a l'estrès hídric i salí de les espècies sobre la base de la seua distribució en la naturalesa i en les anàlisis realitzades en camp i, en funció de la inhibició relativa del seu creixement sota condicions provocades d'estrès; i, ii) avaluar els canvis bioquímics induïts per l'estrès analitzant diferents mecanismes de resposta (inhibició de la fotosíntesi, transport iònic, acumulació de osmolits, mecanismes antioxidants).[EN] Drought and salinity are the environmental factors that most affect plants, although in general Mediterranean plants are well adapted to adverse conditions. Predictions estimate that, due to global warming, environmental conditions will become more stressful, especially in semi-arid and arid areas, such as many areas of the Iberian Peninsula. These conditions may affect the presence of many wild species, especially those that are already threatened, rare or endemic. Both drought and salt stress cause the activation of a series of defence or response mechanisms in plants, which include, among others, the control of ionic transport, the accumulation of compatible solutes or osmolytes, and the activation of antioxidant systems. To contribute to the conservation and/or reintroduction of species of interest in priority habitats, a multidisciplinary study has been carried out covering parameters that may affect their populations, such as climate, soil and accompanying vegetation, together with comparative studies on responses to drought and salinity. To better understand tolerance mechanisms, genetically related species with different levels of tolerance have been included in the study, in addition to taxa of conservation interest. The study has two main objectives: i) to establish the relative tolerance to water and salt stress of the species according to their distribution in nature and based on field analyses and, according to the relative inhibition of their growth under stress-induced conditions; and, ii) to evaluate stress-induced biochemical changes by analysing different mechanisms (inhibition of photosynthesis, ionic transport, osmolyte accumulation, antioxidant mechanisms).This research was partially funded by Project AICO/2017/039 from the Generalitat Valenciana.González Orenga, S. (2021). Mecanismos de tolerancia a estrés salino e hídrico en plantas endémicas, raras o amenazadas [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/168443TESISCompendi

Constitutive and Induced Salt Tolerance Mechanisms and Potential Uses of Limonium Mill. Species

[EN] Limonium is one of the most interesting and biodiverse genera of halophytes, with many species adapted to saline environments. Limonium species have a promising potential as cultivated minor crops as many have ornamental value, or are already used as medicinal plants. Other species are marketed as gourmet food or can be used for decontamination of polluted soils. Design and implementation of specific breeding programmes are needed to fully realise this potential, based on the vast genetic variation and high stress tolerance of wild species within the genus. Most Limonium species are halophytes, but many are also resistant to drought, especially those from the Mediterranean and other arid regions. Such species constitute attractive models for basic research on the mechanisms of stress tolerance, both constitutive and induced. As typical recretohalopyhtes, with excretive salt glands, Limonium species possess remarkable morpho-anatomical traits. Salt tolerance in this genus relies also on ion accumulation in the leaves, the concomitant use of diverse osmolytes for osmotic adjustment, and the activation of efficient antioxidant systems.Work in the authors' laboratories was funded by Generalitat Valenciana, grant AICO/2017/039.González-Orenga, S.; Grigore, M.; Boscaiu, M.; Vicente, O. (2021). Constitutive and Induced Salt Tolerance Mechanisms and Potential Uses of Limonium Mill. Species. Agronomy. 11(3):1-23. https://doi.org/10.3390/agronomy11030413S12311

Antioxidant responses to drought and salinity in Lavandula angustifolia Mill.

Drought and salinity are amongst the most damaging environmental stressors that can affect a plant's life cycle, from germination to senescence. In the present study were analysed the responses to salinity and drought in greenhouse-controlled conditions of two varieties of Lavandula angustifolia. Three-month-old lavender seedlings were subjected to water deficit and salt stress (100, 200 and 300 mM NaCl) during a 30-day period. Complementing a previous analysis focused on stress tolerance mechanisms based on the regulation of ion transport and the synthesis of osmolytes, we have now evaluated the effects of the water deficit and salt treatments on the generation of secondary oxidative stress, by measuring malondialdehyde levels, and the activation of antioxidant systems, both non-enzymatic and enzymatic, determining total phenolic compounds and flavonoids contents and calculating superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase specific activities, respectively, in extracts of control and stressed plants.  The results obtained confirm that both lavender varieties react in the same way to the applied stress treatments, activating the same antioxidant responses. However, some differences were observed when comparing the specific mechanisms triggered by each type of stress. Thus, the oxidative stress induced under drought conditions was counteracted by accumulation of phenolic compounds and flavonoids, without apparent involvement of antioxidant enzymes. Salt stress, on the other hand, in addition to an increase in flavonoid levels also induced superoxide dismutase and catalase activities. These antioxidant responses are likely to contribute to the relatively high tolerance (as compared to most crops) of lavender to drought and salinity

Antioxidant responses to drought and salinity in Lavandula angustifolia Mill.

[EN] Drought and salinity are amongst the most damaging environmental stressors that can affect a plant's life cycle, from germination to senescence. In the present study were analysed the responses to salinity and drought in greenhouse-controlled conditions of two varieties of Lavandula angustifolia. Three-month-old lavender seedlings were subjected to water deficit and salt stress (100, 200 and 300 mM NaCl) during a 30-day period. Complementing a previous analysis focused on stress tolerance mechanisms based on the regulation of ion transport and the synthesis of osmolytes, we have now evaluated the effects of the water deficit and salt treatments on the generation of secondary oxidative stress, by measuring malondialdehyde levels, and the activation of antioxidant systems, both non-enzymatic and enzymatic, determining total phenolic compounds and flavonoids contents and calculating superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase specific activities, respectively, in extracts of control and stressed plants. The results obtained confirm that both lavender varieties react in the same way to the applied stress treatments, activating the same antioxidant responses. However, some differences were observed when comparing the specific mechanisms triggered by each type of stress. Thus, the oxidative stress induced under drought conditions was counteracted by accumulation of phenolic compounds and flavonoids, without apparent involvement of antioxidant enzymes. Salt stress, on the other hand, in addition to an increase in flavonoid levels also induced superoxide dismutase and catalase activities. These antioxidant responses are likely to contribute to the relatively high tolerance (as compared to most crops) of lavender to drought and salinity.Z.S.-V. was the recipient of a pre-doctoral Erasmus Mundus scholarship at the Polytechnic University of Valencia, financed by the European Commission.Szekely-Varga, Z.; González-Orenga, S.; Cantor, M.; Boscaiu, M.; Vicente, O. (2020). Antioxidant responses to drought and salinity in Lavandula angustifolia Mill. Notulae Botanicae Horti Agrobotanici Cluj-Napoca. 48(4):1980-1992. https://doi.org/10.15835/48412150S1980199248

Effect of the Pesticide Endosulfan and Two Different Biostimulants on the Stress Responses of Phaseolus leptostachyus Plants Grown in a Saline Soil

[EN] Soil salinity and the indiscriminate use of agrochemicals has significantly reduced the productivity of the Chinampas agroecosystem in Mexico City. Crop improvement under these stressful conditions may be achieved by soil bioremediation. In this study, we checked the effects of the organochlorine pesticide endosulfan and bioremediation with Penicillium crustosum or a citric waste on the growth of Phaseolus leptostachyus plants in saline soil from the Chinampas area. Biochemical markers associated with specific stress responses were also determined after one month of growth in the different substrates. Plant growth was stimulated by bioremediation of the soil. Both biostimulants reduced the degree of stress affecting the plants, as shown by the increase in photosynthetic pigments and the reduction of proline, malondialdehyde (MDA), and H2O2 contents, and the activation of antioxidant systems. However, the biostimulants appeared to mitigate oxidative stress through different mechanisms. Endosulfan contamination inhibited seed germination¿which was reverted to control values in the presence of the biostimulants¿and further decreased plant growth. No clear patterns of variation of biochemical stress markers were observed combining endosulfan and the biostimulants. In any case, bioremediation with P. crustosum and/or citric waste is recommended to improve the germination and growth of P. leptostachyus plants.Anbu Landa-Faz is grateful to CONACYT, Mexico, for receiving the Ph.D. Scholarship no 306251 to support her stay at Universitat Politecnica de Valencia.Landa-Faz, A.; González-Orenga, S.; Boscaiu, M.; Rodríguez-Vázquez, R.; Vicente, O. (2021). Effect of the Pesticide Endosulfan and Two Different Biostimulants on the Stress Responses of Phaseolus leptostachyus Plants Grown in a Saline Soil. Agronomy. 11(6):1-18. https://doi.org/10.3390/agronomy11061208S11811

Effects of Drought and Salinity on Two Commercial Varieties of Lavandula angustifolia Mill

[EN] Global warming is not only affecting arid and semi-arid regions but also becoming a threat to agriculture in Central and Eastern European countries. The present study analyzes the responses to drought and salinity of two varieties of Lavandula angustifolia cultivated in Romania. Lavender seedlings were subjected to one month of salt stress (100, 200, and 300 mM NaCl) and water deficit (complete withholding of irrigation) treatments. To assess the effects of stress on the plants, several growth parameters and biochemical stress markers (photosynthetic pigments, mono and divalent ions, and different osmolytes) were determined in control and stressed plants after the treatments. Both stress conditions significantly inhibited the growth of the two varieties, but all plants survived the treatments, indicating a relative stress tolerance of the two varieties. The most relevant mechanisms of salt tolerance are based on the maintenance of foliar K+ levels and the accumulation of Ca2+ and proline as a functional osmolyte in parallel with increasing external salinities. Under water stress, significant increases of Na+ and K+ concentrations were detected in roots, indicating a possible role of these cations in osmotic adjustment, limiting root dehydration. No significant differences were found when comparing the stress tolerance and stress responses of the two selected lavender varieties.This research was partially funded by the University of Agricultural Sciences and Veterinary Medicine of Cluj-Napoca, granted to Z.S.-V, and by internal funds of Universitat Politecnica de Valencia. The publication was supported by funds from the National Research Development Projects to finance excellence (PFE)-37/2018-2020 granted by the Romanian Ministry of Research and Innovation.Szekely-Varga, Z.; González-Orenga, S.; Cantor, M.; Jucan, D.; Boscaiu, M.; Vicente, O. (2020). Effects of Drought and Salinity on Two Commercial Varieties of Lavandula angustifolia Mill. Plants. 9(5):1-20. https://doi.org/10.3390/plants9050637S1209

Adaptability of invasive plants to climate change

[EN] Climate change represents one of the greatest environmental challenges of the 21st century, accentuated by deforestation and the degradation of habitats. Changes in vital aspects such as temperature, the amount and distribution of rainfall or the frequency of extreme meteorological phenomena will probably negatively affect ecosystems. The possibilities of invasion will predictably increase, being endemic species especially vulnerable to the effects of climate change. Invasive species are extremely adaptable to climate variability, as evidenced by their current large latitudinal ranges. Generally, invasive plants also have rapid dispersal characteristics, allowing them to vary their ranges in response to changing climatic conditions rapidly. As a result, these species could become more dominant in many areas under changing climatic conditions. In many situations, the environmental stress generated by climate change and invasive plants are synergistic: invasive species can exacerbate the impacts of climate change on ecosystems, and in the same way, climate change can allow new invasions.S.G-O acknowledges a 'Margarita Salas' postdoctoral contract from Universitat Politècnica de València and the Spanish Ministry of Universities, supported by the European Union - Next Generation fundsGonzález-Orenga, S.; Boscaiu, M.; Verdeguer Sancho, MM.; Sánchez-Moreiras, AM.; González, L.; Vicente, O. (2022). Adaptability of invasive plants to climate change. AgroLife Scientific Journal (Online). 11(2):58-65. https://doi.org/10.17930/AGL202227586511

Effect of a Biostimulant Based on Polyphenols and Glycine Betaine on Tomato Plants¿ Responses to Salt Stress

[EN] Climate change accentuates abiotic stress conditions putting at risk several commercial cultivars particularly vulnerable to salinity in the early stages of development, which makes adopting new technologies in tune with the environment necessary to mitigate its impact. In this study, we tested the possible effects of a commercial biostimulant (BALOX®) on enhancing salt stress tolerance in salt-treated tomato plants, analysing plant growth and several stress biochemical markers: photosynthetic pigments, ion contents in roots and leaves, leaf concentrations of different osmolytes, oxidative stress markers, non-enzymatic antioxidants, and the specific activities of major antioxidant enzymes. The experimental design consisted of three soil salinity levels (non-saline, saline, and very saline), two biostimulant doses (0.4 mL and 0.8 mL of the BALOX® stock per litre of irrigation water), and the non-treated control (without biostimulant), evaluated at 30 and 60 days of treatment. The biostimulant favoured plant growth, especially at the root level and in saline soils. In addition, it helped reduce Na+ and Cl uptake by the roots and seemed to stimulate, to some extent, K+ and Ca2+ transport to the aerial part of the plant. The BALOX® application significantly reduced the level of stress affecting the plants in saline soils, as shown by the decrease in the contents of proline and oxidative stress biomarkers and the activity of salt-induced antioxidant enzymes. Some of the biostimulant effects were also observed under low salinity conditions; therefore, in addition to enhancing salt stress responses, BALOX® appears to stimulate the growth of tomato plants through a general improvement of photosynthesis and primary metabolism.This research was partly funded by the company Innovak Global and partly by UPV through internal funds to S.I.-A., M.B. and O.V.Zuzunaga-Rosas, J.; González-Orenga, S.; Tofei, AM.; Boscaiu, M.; Moreno-Ramón, H.; Ibañez Asensio, S.; Vicente, O. (2022). Effect of a Biostimulant Based on Polyphenols and Glycine Betaine on Tomato Plants¿ Responses to Salt Stress. Agronomy. 12(9):1-26. https://doi.org/10.3390/agronomy1209214212612

Effect of acetylsalicylic acid and ammonium sulphate on productive and physiological parameters in Stipa caudata under water shortage conditions

Stipa caudata is a grass native to low rainfall areas in Argentina and Chile, considered an excellent potential candidate for biofuel production or soil restoration programmes. This study aimed at analysing the effects of ammonium sulphate (AMS) and acetylsalicylic acid (ASA) on the productivity and biochemical traits of plants of this species under water scarcity conditions. The experimental work was carried out on plants grown outdoors using a randomised block plot design. Several yield and biochemical parameters related to resistance to water scarcity were analysed in plants treated with AMS or ASA. Plants in the treatments with ASA and AMS had higher total chlorophyll content than the others. Concerning ion content, water-restricted plants treated with AMS had similar values to irrigated plants. Regarding the osmoprotectants and antioxidants, treated plants had increased concentrations of proline and total flavonoids. Under water stress, plants had higher APX activity and there was an A x B interaction for CAT and SOD activity. The results obtained show that the use of ASA and AMS in some crops or in environmental restoration programmes could be a useful tool to cope with future climate scenarios of water scarcity

Responses to Salinity in Four Plantago Species from Tunisia

[EN] The genus Plantago is particularly interesting for studying the mechanisms of salt tolerance in plants, as it includes both halophytes and glycophytes, as well as species adapted to xeric environments. In this study, the salt stress responses of two halophytes, P. crassifolia and P. coronopus, were compared with those of two glycophytes, P. ovata and P. afra. Plants obtained by seed germination of the four species, collected in different regions of Tunisia, were subjected to increasing salinity treatments for one month under greenhouse conditions. Morphological traits and biochemical parameters, such as ion accumulation and the leaf contents of photosynthetic pigments, osmolytes, oxidative stress markers and antioxidant metabolites, were measured after the treatments. Salt-induced growth inhibition was more pronounced in P. afra, and only plants subjected to the lowest applied NaCl concentration (200 mM) survived until the end of the treatments. The biochemical responses were different in the two groups of plants; the halophytes accumulated higher Na+ and proline concentrations, whereas MDA levels in their leaves decreased, indicating a lower level of oxidative stress. Overall, the results showed that P. coronopus and P. crassifolia are the most tolerant to salt stress, and P. afra is the most susceptible of the four species. Plantago ovata is also quite resistant, apparently by using specific mechanisms of tolerance that are more efficient than in the halophytes, such as a less pronounced inhibition of photosynthesis, the accumulation of higher levels of Cl¿ ions in the leaves, or the activation of K+ uptake and transport to the aerial part under high salinity conditions.This research was supported by internal funds of Universitat Politecnica de Valencia to O.V. and M.B.Ltaeif, HB.; Sakhraoui, A.; González-Orenga, S.; Landa Faz, A.; Boscaiu, M.; Vicente, O.; Rouz, S. (2021). Responses to Salinity in Four Plantago Species from Tunisia. Plants. 10(7):1-20. https://doi.org/10.3390/plants10071392S12010