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Miscanthus is a perennial grass suitable for the production of lignocellulosic biomass on marginal lands. The effects of salt stress on Miscanthus cell wall composition and its consequences on biomass quality have nonetheless received relatively little attention. In this study, we investigated how exposure to moderate (100 mM NaCl) or severe (200 mM NaCl) saline growing conditions altered the composition of both primary and secondary cell wall components in the stems of 15 Miscanthus sinensis genotypes. The exposure to stress drastically impacted biomass yield and cell wall composition in terms of content and structural features. In general, the observed compositional changes were more pronounced under severe stress conditions and were more apparent in genotypes with a higher sensitivity towards stress. Besides a severely reduced cellulose content, salt stress led to increased pectin content, presumably in the form of highly branched rhamnogalacturonan type I. Although salt stress had a limited effect on the total lignin content, the acid-soluble lignin content was strongly increased in the most sensitive genotypes. This effect was also reflected in substantially altered lignin structures and led to a markedly reduced incorporation of syringyl subunits and p-coumaric acid moieties. Interestingly, plants that were allowed a recovery period after stress ultimately had a reduced lignin content compared to those continuously grown under control conditions. In addition, the salt stress-induced cell wall alterations contributed to an improved enzymatic saccharification efficiency.

New biomass crop hybrids for bioeconomic expansion require yield projections to determine their potential for strategic land use planning in the face of global challenges. Our biomass growth simulation incorporates radiation interception and conversion efficiency. Models often use leaf area to predict interception which is demanding to determine accurately, so instead we use low-cost rapid light interception measurements using a simple laboratory-made line ceptometer and relate the dynamics of canopy closure to thermal time, and to measurements of biomass. We apply the model to project the European biomass potentials of new market-ready hybrids for 2020–2030. Field measurements are easier to collect, the calibration is seasonally dynamic and reduces influence of weather variation between field sites. The model obtained is conservative, being calibrated by crops of varying establishment and varying maturity on less productive (marginal) land. This results in conservative projections of miscanthus hybrids for 2020–2030 based on 10% land use conversion of the least (productive) grassland and arable for farm diversification, which show a European potential of 80.7–89.7 Mt year−1 biomass, with potential for 1.2–1.3 EJ year−1 energy and 36.3–40.3 Mt year−1 carbon capture, with seeded Miscanthus sacchariflorus × sinensis displaying highest yield potential. Simulated biomass projections must be viewed in light of the field measurements on less productive land with high soil water deficits. We are attempting to model the results from an ambitious and novel project combining new hybrids across Europe with agronomy which has not been perfected on less productive sites. Nevertheless, at the time of energy sourcing issues, seed-propagated miscanthus hybrids for the upscaled provision of bioenergy offer an alternative source of renewable energy. If European countries provide incentives for growers to invest, seeded hybrids can improve product availability and biomass yields over

Ornamental plant species introduced into new environments can exhibit an invasive potential and adaptability to abiotic stress factors. In this study, the drought stress responses of four potentially invasive ornamental grass species (Cymbopogon citratus, Cortaderia selloana, Pennisetum alopecuroides and P. setaceum) were analysed. Several seed germination parameters were determined under increasing polyethylene glycol (PEG 6000) concentrations. Additionally, plants in the vegetative stage were subjected to intermediate and severe water stress treatments for four weeks. All species registered high germination rates in control conditions (no stress treatment), even at high PEG concentrations, except C. citratus, which did not germinate at −1 MPa osmotic potential. Upon applying the water stress treatments, P. alopecuroides plants showed the highest tolerance, and C. citratus appeared the most susceptible to drought. Stress-induced changes in several biochemical markers (photosynthetic pigments, osmolytes, antioxidant compounds, root and shoot Na+ and K+ contents), highlighted different responses depending on the species and the stress treatments. Basically, drought tolerance seems to depend to a large extent on the active transport of Na+ and K+ cations to the aerial part of the plants, contributing to osmotic adjustment in all four species and, in the case of the most tolerant P. alopecuroides, on the increasing root K+ concentration under water deficit conditions. The study shows the invasive potential of all species, except C. citratus, in dry areas such as the Mediterranean region, especially in the current climate change scenario. Particular attention should be given to P. alopecuroides, which is widely commercialised in Europe as ornamental.

Fungal pretreatment of plant biomass is often assessed by using single plant genotypes and single fungal strains, but can the process be improved by harmonizing both, thus selecting specific substrate-fungus combinations? To tackle this question, we treated four Miscanthus sinensis genotypes with four Ceriporiopsis subvermispora strains and thoroughly analyzed substrates and treated residues. The M. sinensis genotypes differed in cellulose, hemicellulose, and lignin contents and lignin-wise diverged in subunit and linkage composition and the incorporation of hydroxycinnamic acids and tricin. Independently of the M. sinensis genotype used, C. subvermispora strain MES13904 outperformed the other three strains in extent and selectivity of delignification and consistently generated the highest enzymatic residual carbohydrate conversion and structural changes in the residual lignin. The “best” substrate-fungus combination gave 63% w/w delignification and a total enzymatic glucose yield of 66% w/w, while the “worst” combination led to 3% w/w lignin removal only and negligible glucose yield improvement. Our study highlights that white-rot fungal treatment of plant biomass is driven by both compositional and structural features of the substrate as well as the genetic makeup of the fungal strain used. These insights contribute to expediting the biological valorization of lignocellulose and ultimately to enabling more controlled fungal pretreatments.

Syntenic cell wall QTLs (SQTLs) can identify genetic determinants of biomass traits in understudied species based on results from model crops. However, their effective use in plant breeding requires SQTLs to display intraspecific allelic variability and to predict causative loci in other populations/species than the ones used for SQTLs identification. In this study, genome assemblies from different accessions of Arabidopsis, rapeseed, tomato, rice, Brachypodium and maize were used to evaluate the intraspecific variability of SQTLs. In parallel, a genome-wide association study (GWAS) on cell wall quality traits was performed in miscanthus to verify the colocalization between GWAS loci and miscanthus SQTLs. Finally, an analogous approach was applied on a set of switchgrass cell wall QTLs retrieved from the literature. These analyses revealed large SQTLs intraspecific genetic variability, ranging from presence–absence gene variation to SNPs/INDELs and changes in coded proteins. Cell wall genes displaying gene dosage regulation, such as PAL and CAD, displayed presence–absence variation in Brachypodium and rapeseed, while protein INDELs were detected for the Brachypodium homologs of the rice brittle culm-like 8 locus, which may likely impact cell wall quality. Furthermore, SQTLs significantly colocalized with the miscanthus and switchgrass QTLs, with relevant cell wall genes being retained in colocalizing regions. Overall, SQTLs are useful tools to screen germplasm for relevant genes and alleles to improve biomass quality and can increase the efficiency of plant breeding in understudied biomass crops.

This dataset contains 100 sets of 91 random QTL regions from the genome of Miscanthus sinensis that mirror the basepair size distribution of 91 QTLs that were found in Miscanthus sinensis through genome-wide association analysis (GWAS) for multiple traits related to biomass (cell wall) quality. The 100 sets of random QTL regions were used in the publication attached to this dataset to perform a permutation analysis to test for co-localization between a set of syntenic QTLs for cell wall quality previously mapped in Miscanthus and the QTLs detected by GWAS (see above). The 100 sets of random QTL regions have been produced in R, by applying the size distribution of GWAS QTLs as constraint for determining the size of random QTLs. Random QTLs could be picked across the whole miscanthus genome, to ensure complete randomness.

Miscanthus, a C4 perennial rhizomatous grass from Asia is a leading candidate for the supply of sustainable biomass needed to grow the bioeconomy. European Miscanthus breeding programmes have recently produced a new range of seeded hybrids with the objective of increasing scalability to large acreages limited by current clonal propagation. For the EU-GRACE project, new replicated field trials were established in seven locations across Europe in 2018 with eight intraspecific M. sinensis hybrids (sin × sin) and six M. sacchariflorus × M. sinensis (sac × sin) from Dutch and UK breeding programmes, respectively, with clonal Miscanthus × giganteus. The planting density of the sin × sin was double that of sac × sin (30,000 & 15,000 plants ha−1), creating commercially relevant upscaling comparisons between systems. Over the first 3 years, the establishment depended on location and hybrid. The mature sin × sin hybrids formed tight tufts of shoots up to 2.5 m tall which flower and senesce earlier than the taller sac × sin hybrids. Following the third growing season, the highest yields were recorded in Northern Italy at a low altitude (average 13.7 (max 21) Mg DM ha−1) and the lowest yielding was on the industrially damaged marginal land site in Northern France (average 7.0 (max 10) Mg DM ha−1). Moisture contents at spring harvest were lowest in Croatia (21.7%) and highest in Wales, UK (41.6%). Overall, lower moisture contents at harvest, which are highly desirable for transport, storage and for most end-use applications, were found in sin × sin hybrids than sac × sin (30% and 40%, respectively). Yield depended on climate interactions with the hybrid and their associated planting systems. The sin × sin hybrids appeared better adapted to northern Europe and sac × sin hybrids to southern Europe. Longer-term yield observations over crop lifespans will be needed to explore the biological (yield persistence) and economic costs and benefits of the different hybrid systems.

Lignocellulosic crops are attractive bioresources for energy and chemicals production within a sustainable, carbon circular society. Miscanthus is one of the perennial grasses that exhibits great potential as a dedicated feedstock for conversion to biobased products in integrated biorefineries. The current biorefinery strategies are primarily focused on polysaccharide valorization and require severe pretreatments to overcome the lignin barrier. The need for such pretreatments represents an economic burden and impacts the overall sustainability of the biorefinery. Hence, increasing its efficiency has been a topic of great interest. Inversely, though pretreatment will remain an essential step, there is room to reduce its severity by optimizing the biomass composition rendering it more exploitable. Extensive studies have examined the miscanthus cell wall structures in great detail, and pinpointed those components that affect biomass digestibility under various pretreatments. Although lignin content has been identified as the most important factor limiting cell wall deconstruction, the effect of polysaccharides and interaction between the different constituents play an important role as well. The natural variation that is available within different miscanthus species and increased understanding of biosynthetic cell wall pathways have specified the potential to create novel accessions with improved digestibility through breeding or genetic modification. This review discusses the contribution of the main cell wall components on biomass degradation in relation to hydrothermal, dilute acid and alkaline pretreatments. Furthermore, traits worth advancing through breeding will be discussed in light of past, present and future breeding efforts.

[EN] Climate change and its detrimental effects on agricultural production, freshwater availability and biodiversity accentuated the need for more stress-tolerant varieties of crops. This requires unraveling the underlying pathways that convey tolerance to abiotic stress in wild relatives of food crops, industrial crops and ornamentals, whose tolerance was not eroded by crop cycles. In this work we try to demonstrate the feasibility of such strategy applying and investigating the effects of saline stress in different species and cultivars of Portulaca. We attempted to unravel the main mechanisms of stress tolerance in this genus and to identify genotypes with higher tolerance, a procedure that could be used as an early detection method for other ornamental and minor crops. To investigate these mechanisms, six-week-old seedlings were subjected to saline stress for 5 weeks with increasing salt concentrations (up to 400 mM NaCl). Several growth parameters and biochemical stress markers were determined in treated and control plants, such as photosynthetic pigments, monovalent ions (Na+, K+ and Cl-), different osmolytes (proline and soluble sugars), oxidative stress markers (malondialdehyde-a by-product of membrane lipid peroxidation-MDA) and non-enzymatic antioxidants (total phenolic compounds and total flavonoids). The applied salt stress inhibited plant growth, degraded photosynthetic pigments, increased concentrations of specific osmolytes in both leaves and roots, but did not induce significant oxidative stress, as demonstrated by only small fluctuations in MDA levels. All Portulaca genotypes analyzed were found to be Na+ and Cl- includers, accumulating high amounts of these ions under saline stress conditions, but P. grandiflora proved to be more salt tolerant, showing only a small reduction under growth stress, an increased flower production and the lowest reduction in K+/Na+ rate in its leaves.

[EN] Background and aims: Morphological and biochemical traits of four halophytes of the genus Limonium were analysed in plants sampled from salt marshes in SE Spain. This work aimed to explore the mechanism(s) behind the adaptation of these species to stressful habitats, with particular emphasis on responses to drought. Methods: Plants of each species together with soil samples were collected in summer, which is the most stressful season in the Mediterranean. Soil parameters and plant morphological traits were determined, and the levels of several biochemical stress markers in plants were measured using spectrophotometric assays. A multivariate analysis was performed to correlate soil and plant data. Results: Morphological characteristics regarding the underground system topology and several biochemical traits (higher foliar Ca2+, sucrose and glucose, and lower proline, glycine-betaine and fructose) clearly separate L. santapolense individuals from plants of the other three species. Conclusions: Drought tolerance of L. santapolense in the field is mostly dependent on morphological adaptations: when growing in an arid location, plants of this species develop long taproots that can extract water from the deep, moist layers of the soil.

Climate change and its detrimental effects on agricultural production, freshwater availability and biodiversity accentuated the need for more stress-tolerant varieties of crops. This requires unraveling the underlying pathways that convey tolerance to abiotic stress in wild relatives of food crops, industrial crops and ornamentals, whose tolerance was not eroded by crop cycles. In this work we try to demonstrate the feasibility of such strategy applying and investigating the effects of saline stress in different species and cultivars of Portulaca. We attempted to unravel the main mechanisms of stress tolerance in this genus and to identify genotypes with higher tolerance, a procedure that could be used as an early detection method for other ornamental and minor crops. To investigate these mechanisms, six-week-old seedlings were subjected to saline stress for 5 weeks with increasing salt concentrations (up to 400 mM NaCl). Several growth parameters and biochemical stress markers were determined in treated and control plants, such as photosynthetic pigments, monovalent ions (Na+, K+ and Cl−), different osmolytes (proline and soluble sugars), oxidative stress markers (malondialdehyde—a by-product of membrane lipid peroxidation—MDA) and non-enzymatic antioxidants (total phenolic compounds and total flavonoids). The applied salt stress inhibited plant growth, degraded photosynthetic pigments, increased concentrations of specific osmolytes in both leaves and roots, but did not induce significant oxidative stress, as demonstrated by only small fluctuations in MDA levels. All Portulaca genotypes analyzed were found to be Na+ and Cl− includers, accumulating high amounts of these ions under saline stress conditions, but P. grandiflora proved to be more salt tolerant, showing only a small reduction under growth stress, an increased flower production and the lowest reduction in K+/Na+ rate in its leaves.

[EN] Limonium is a genus represented in the Iberian Peninsula by numerous halophytic species that are a ected in nature by salinity, and often by prolonged drought episodes. Responses to water deficit have been studied in four Mediterranean Limonium species, previously investigated regarding salt tolerance mechanisms. The levels of biochemical markers, associated with specific responses¿photosynthetic pigments, mono- and divalent ions, osmolytes, antioxidant compounds and enzymes¿were determined in the control and water-stressed plants, and correlated with their relative degree of stress-induced growth inhibition. All the tested Limonium taxa are relatively resistant to drought on the basis of both the constitutive presence of high leaf ion levels that contribute to osmotic adjustment, and the stress-induced accumulation of osmolytes and increased activity of antioxidant enzymes, albeit with di erent qualitative and quantitative induction patterns. Limonium santapolense activated the strongest responses and clearly di ered from Limonium virgatum, Limonium girardianum, and Limonium narbonense, as indicated by cluster and principal component analysis (PCA) analyses in agreement with its drier natural habitat, and compared to that of the other plants. Somewhat surprisingly, however, L. santapolense was the species most a ected by water deficit in growth inhibition terms, which suggests the existence of additional mechanisms of defense operating in the field that cannot be mimicked in greenhouses.

[EN] The increasing frequency and intensity of drought periods is a serious threat for agriculture, prompting research to select and develop crop species and cultivars with enhanced water stress tolerance. Drought responses were studied in four ornamental Sedum species under controlled greenhouse conditions, by withholding watering of the plants for four weeks. Determination of growth parameters (stem length, fresh weight) allowed establishing the relative degree of tolerance of the selected species as S. spurium>S. ochroleucum>S. sediforme>S. album. The levels of photosynthetic pigments (chlorophylls a and b and total carotenoids), oxidative stress [using malondialdehyde (MDA) as a marker], non-enzymatic antioxidants (total phenolic compounds and total flavonoids) and putative osmolytes [proline (Pro) and total soluble sugars] were measured in leaves of control and stressed plants, to correlate drought tolerance with the activation of specific response mechanisms. The results obtained indicate that a higher tolerance to water deficit in Sedum is associated with: a) relatively lower stressinduced degradation of chlorophylls and carotenoids, especially of the latter (which did not decrease in waterstressed plants of S. spurium, the most tolerant species, whereas it was reduced to about 40% of the control in S. album, the most sensitive); b) no increase in MDA levels, reflecting the lack of drought-induced oxidative stress; and c) higher Pro contents in the non-stressed controls of the taxa most resistant to drought, which could be the basis of constitutive mechanisms of tolerance. However, Pro contribution to drought tolerance in Sedum must be based on an `osmoprotectant¿ role, as its concentrations, below 16 ¿mol g¿1 DW in all cases, are too low to have any significant osmotic effect. The identification of these biochemical markers of drought tolerance should help to develop rapid and efficient screening procedures to select Sedum taxa with enhanced tolerance when c

[EN] This study attempted to determine short-term responses to drought and salt stress in different Silene vulgaris genotypes and to identify potential abiotic stress biochemical indicators in this species. Four populations from contrasting habitats were subjected to drought and three levels of salinity under controlled greenhouse conditions. The determination of several growth parameters after the stress treatments allowed for ranking the tolerance to stress of the four analyzed populations on the basis of their relative degree of stress-induced growth inhibition. This was then correlated with changes in the leaf levels of monovalent ions (Na+, Cl-, and K+), photosynthetic pigments (chlorophylls a and b, carotenoids), osmolytes (total soluble sugars, proline), and non-enzymatic antioxidants (total phenolic compounds and flavonoids). Despite the observed differences, all four populations appeared to be relatively tolerant to both stress conditions, which in general did not cause a significant degradation of photosynthetic pigments and did not generate oxidative stress in the plants. Drought and salinity tolerance in S. vulgaris was mostly dependent on the use of Na+ and K+ for osmotic adjustment under stress, a mechanism that appeared to be constitutive, and not stress-induced, since relatively high concentrations of these cations (without reaching toxic levels) were also present in the leaves of control plants. The inhibition of additional transportation of toxic ions to the leaves, in response to increasing external salinity, seemed to be a relevant mechanism of tolerance, specifically to salt stress, whereas accumulation of soluble sugars under drought conditions may have contributed to tolerance to drought.

[EN] European larch (Larix decidua Mill.) has been reported either as more tolerant or as more sensitive to drought than conifers with perennial leaves. Previous studies have revealed that Carpathian populations of European larch display a high genetic variability. A comparative study of the responses of these populations to drought stress at the seedling stage might allow the identification of drought tolerant genotypes and reliable drought stress biomarkers, which could be eventually used for the early detection of drought effects in larch, not only under control greenhouse conditions, but also in their natural stands. Growth responses were analyzed in larch seedlings from six Romanian Carpathian populations, submitted to one month of mild drought stress under controlled conditions. Levels of photosynthetic pigments (chlorophylls a and b, and carotenoids), osmolytes (proline and total soluble sugars), monovalent cations (Na+ and K+), and malondialdehyde (MDA) and non-enzymatic antioxidants (total phenolics and flavonoids) were compared with control treatments and between populations. Growth and the pattern of the biochemical responses were very similar in the six populations. Drought stress lead to stem length decrease in all population, whereas reduction of fresh weight of needles was significant only in one population (BVVC), and reduction of water content of needles in two populations (BVVC and GuHo). The optimal biochemical traits for an early detection of drought symptoms in this species is the increase-in most populations-of total soluble sugars, MDA, and total phenolic compounds, whereas K+ reduction was significant in all populations. Photosynthetic pigments remained unchanged, except for the Anin population where they were reduced under stress. Multivariate principal component and hierarchical clustering analyses confirmed the impact of drought in the growth and physiology of European larch, and revealed that the humidity of the substrate was positively c

Limonium is a genus represented in the Iberian Peninsula by numerous halophytic species that are affected in nature by salinity, and often by prolonged drought episodes. Responses to water deficit have been studied in four Mediterranean Limonium species, previously investigated regarding salt tolerance mechanisms. The levels of biochemical markers, associated with specific responses—photosynthetic pigments, mono- and divalent ions, osmolytes, antioxidant compounds and enzymes—were determined in the control and water-stressed plants, and correlated with their relative degree of stress-induced growth inhibition. All the tested Limonium taxa are relatively resistant to drought on the basis of both the constitutive presence of high leaf ion levels that contribute to osmotic adjustment, and the stress-induced accumulation of osmolytes and increased activity of antioxidant enzymes, albeit with different qualitative and quantitative induction patterns. Limonium santapolense activated the strongest responses and clearly differed from Limonium virgatum, Limonium girardianum, and Limonium narbonense, as indicated by cluster and principal component analysis (PCA) analyses in agreement with its drier natural habitat, and compared to that of the other plants. Somewhat surprisingly, however, L. santapolense was the species most affected by water deficit in growth inhibition terms, which suggests the existence of additional mechanisms of defense operating in the field that cannot be mimicked in greenhouses.

European larch (Larix decidua Mill.) has been reported either as more tolerant or as more sensitive to drought than conifers with perennial leaves. Previous studies have revealed that Carpathian populations of European larch display a high genetic variability. A comparative study of the responses of these populations to drought stress at the seedling stage might allow the identification of drought tolerant genotypes and reliable drought stress biomarkers, which could be eventually used for the early detection of drought effects in larch, not only under control greenhouse conditions, but also in their natural stands. Growth responses were analyzed in larch seedlings from six Romanian Carpathian populations, submitted to one month of mild drought stress under controlled conditions. Levels of photosynthetic pigments (chlorophylls a and b, and carotenoids), osmolytes (proline and total soluble sugars), monovalent cations (Na+ and K+), and malondialdehyde (MDA) and non-enzymatic antioxidants (total phenolics and flavonoids) were compared with control treatments and between populations. Growth and the pattern of the biochemical responses were very similar in the six populations. Drought stress lead to stem length decrease in all population, whereas reduction of fresh weight of needles was significant only in one population (BVVC), and reduction of water content of needles in two populations (BVVC and GuHo). The optimal biochemical traits for an early detection of drought symptoms in this species is the increase—in most populations—of total soluble sugars, MDA, and total phenolic compounds, whereas K+ reduction was significant in all populations. Photosynthetic pigments remained unchanged, except for the Anin population where they were reduced under stress. Multivariate principal component and hierarchical clustering analyses confirmed the impact of drought in the growth and physiology of European larch, and revealed that the humidity of the substrate was positively correl

Limonium is a genus represented in the Iberian Peninsula by numerous halophytic species that are affected in nature by salinity, and often by prolonged drought episodes. Responses to water deficit have been studied in four Mediterranean Limonium species, previously investigated regarding salt tolerance mechanisms. The levels of biochemical markers, associated with specific responses—photosynthetic pigments, mono-and divalent ions, osmolytes, antioxidant compounds and enzymes—were determined in the control and water-stressed plants, and correlated with their relative degree of stress-induced growth inhibition. All the tested Limonium taxa are relatively resistant to drought on the basis of both the constitutive presence of high leaf ion levels that contribute to osmotic adjustment, and the stress-induced accumulation of osmolytes and increased activity of antioxidant enzymes, albeit with different qualitative and quantitative induction patterns. Limonium santapolense activated the strongest responses and clearly differed from Limonium virgatum, Limonium girardianum, and Limonium narbonense, as indicated by cluster and principal component analysis (PCA) analyses in agreement with its drier natural habitat, and compared to that of the other plants. Somewhat surprisingly, however, L. santapolense was the species most affected by water deficit in growth inhibition terms, which suggests the existence of additional mechanisms of defense operating in the field that cannot be mimicked in greenhouses.

[EN] Larix decidua, the European larch, does not grow in natural saline areas, but it can be affected by salinity either by the common practice of winter de-icing of mountain roads with NaCl, or when grown as an ornamental tree in urban areas by the use of low quality, salinised irrigation water. In the present study, the responses to salt stress of young seedlings obtained from seeds of seven Carpathian larch populations were analysed. After 30 days of treatments with 150 mM NaCl, growth and biochemical parameters were determinated. Salt stress inhibited growth of all seedlings, as shown by the relative reduction of stem length and fresh weight, and induced significant changes in the needle levels of several biochemical stress markers. Seedlings from all populations showed a marked reduction of photosynthetic pigments contents and an increase of proline and malondialdehyde (MDA) concentrations. Under salt stress, plants accumulated Na+ and Cl- in the needles, whereas K+ was maintained at a steady level. Responses of seedlings from the different populations were similar, with only small quantitative differences that did not allow the identification of more salt tolerant genotypes. However, the study revealed that several of the biochemical markers mentioned above can be suitable for the rapid and non-destructive assessment of the effects of salinity in European larch.

[EN] Due to its high tolerance to abiotic stress, barley (Hordeum vulgare) is cultivated in many arid areas of the world. In the present study, we evaluate the tolerance to water stress (drought) in nine accessions of ¿Ardhaoui¿ barley landraces from different regions of Tunisia. The genetic diversity of the accessions is evaluated with six SSR markers. Seedlings from the nine accessions are subjected to water stress by completely stopping irrigation for three weeks. A high genetic diversity is detected among the nine accessions, with no relationships between genetic distance and geographical or ecogeographical zone. The analysis of growth parameters and biochemical markers in the water stress-treated plants in comparison to their respective controls indicated great variability among the studied accessions. Accession 2, from El May Island, displayed high tolerance to drought. Increased amounts of proline in water-stressed plants could not be correlated with a better response to drought, as the most tolerant accessions contained lower levels of this osmolyte. A good correlation was established between the reduction of growth and degradation of chlorophylls and increased levels of malondialdehyde and total phenolics. These biochemical markers may be useful for identifying drought tolerant materials in barley

Tesis por compendio, [EN] Abstract Introduction Salinity and drought are the most important environmental stress conditions reducing crop yields worldwide and limiting the distribution of wild plants in nature. Soil salinity, especially secondary salinity caused by anthropogenic practices, such as prolonged irrigation, lead to substantial agricultural yield losses, especially in arid and semiarid regions. Drought, caused by reduced water content in the soil, occurs due to disorders in nature's water cycle, chiefly when evapotranspiration exceeds precipitation in a certain area, to the point where soil water reserves can no longer support plant growth. Drought and salt stress trigger the activation of a series of basic stress mechanisms that includes among others, the control of ion transport, exclusion and compartmentalization, as well as the accumulation of compatible solutes ('osmolytes'), and the activation of antioxidant systems. These mechanisms are conserved in all plants, stress tolerant and sensitive alike, and don't necessarily confer tolerance. To decipher those mechanisms and have a better understanding on the contribution of different stress responses to the stress tolerance of a given species, we have carried out comparative studies on the responses to drought and salinity in a number of genetically related taxa with different tolerance potentials. Methodology The experimental approach was mostly based on i) establishing the relative tolerance to water and salt stress in the studied species from their distribution in nature (in the case of wild species) and through the relative inhibition of growth in the presence of stress, and ii) correlating changes in the levels of biochemical 'stress markers' associated to specific response pathways (ion transport, osmolyte accumulation¿) upon stress treatments, with the already established relative tolerance to stress. This strategy proved to be appropriate to distinguish mere general responses to stress from those mechanisms relevant, [ES] Resumen Introducción La salinidad y la sequía son las condiciones de estrés ambiental más importantes, que reducen los rendimientos de los cultivos en todo el mundo y que limitan la distribución de las plantas silvestres en la naturaleza. La salinidad del suelo, especialmente la salinización secundaria causada por prácticas antropogénicas, como la irrigación prolongada, conducen a pérdidas importantes de rendimiento agrícola, especialmente en las regiones áridas y semiáridas. La sequía, provocada por la reducción de contenido de agua en el suelo, se produce debido a alteraciones en el ciclo del agua en la naturaleza, principalmente cuando la evapotranspiración excede la precipitación en un área determinada, hasta el punto que las reservas de agua del suelo ya no pueden soportar el crecimiento de la planta. La sequía y el estrés salino desencadenan la activación de una serie de mecanismos básicos de respuesta, que incluyen entre otros el control del transporte, la exclusión y la compartimentación de iones, así como la acumulación de solutos compatibles ('osmolitos'), y la activación de sistemas antioxidantes. Estos mecanismos están conservados en todas las plantas, tolerantes y sensibles a estrés por igual, y no confieren necesariamente tolerancia. Para descifrar estos mecanismos y conseguir una mejor comprensión de la contribución de diferentes respuestas a estrés a la tolerancia al estrés en una especie dada, hemos llevado a cabo estudios comparativos sobre las respuestas a la sequía y la salinidad, en un número de taxones relacionados genéticamente con diferentes potenciales de tolerancia. Metodología El enfoque experimental se basó principalmente en i) establecer la tolerancia relativa al estrés hídrico y al estrés salino en las especies estudiadas, a partir de su distribución en la naturaleza (en el caso de especies silvestres) y atendiendo a la inhibición relativa de su crecimiento en presencia de estrés, y ii) correlacionar cambios en los niveles de 'marc, [CA] Resum Introducció La salinitat i la sequera són les condicions d'estrès ambiental més importants, que redueixen els rendiments dels cultius a tot el món i que limiten la distribució de les plantes silvestres en la naturalesa. La salinitat del sòl, especialment la salinització secundària causada per pràctiques antropogèniques, com la irrigació perllongada, condueixen a pèrdues importants de rendiment agrícola, especialment en les regions àrides i semiàrides. La sequera, provocada per la reducció de contingut d'aigua en el sòl, es produeix a causa d'alteracions en el cicle de l'aigua en la naturalesa, principalment quan la evapotranspiració excedeix la precipitació en un àrea determinada, fins al punt que les reserves d'aigua del sòl ja no poden suportar el creixement de la planta. La sequera i l'estrès salí desencadenen l'activació d'una sèrie de mecanismes bàsics de resposta, que inclouen entre uns altres el control del transport, l'exclusió i la compartimentació d'ions, així com l'acumulació de soluts compatibles ('osmolits'), i l'activació de sistemes antioxidants. Aquests mecanismes estan conservats en totes les plantes, tolerants i sensibles a estrès per igual, i no confereixen necessàriament tolerància. Per a desxifrar aquests mecanismes i aconseguir una millor comprensió de la contribució de diferents respostes a estrès a la tolerància a l'estrès en una espècie donada, hem dut a terme estudis comparatius sobre les respostes a la sequera i la salinitat, en un nombre de taxons relacionats genèticament amb diferents potencials de tolerància. Metodologia L'enfocament experimental es va basar principalment en i) establir la tolerància relativa a l'estrès hídric i a l'estrès salí en les espècies estudiades, a partir de la seua distribució en la naturalesa (en el cas d'espècies silvestres) i atenent a la inhibició relativa de el seu creixement en presència d'estrès, i ii) correlacionar canvis en els nivells de 'marcadors bioquímics d'estrès' associats a vies esp

[EN] The effects of salt and water deficit on seed germination and early seedling growth were studied in six Portulaca accessions (P. oleracea L. ssp. oleracea, P. grandiflora Hook., P. grandiflora cvs. `Sundial Mango¿, `Double Pink¿ and `Double White¿, and P. halimoides L.). The aims of the study were to evaluate their responses to abiotic stress and to establish the relative degree of tolerance of the selected taxa. Seeds were germinated in the presence of increasing concentrations of NaCl or polyethylene glycol 6000 (to mimic drought conditions), generating the same osmotic potentials: 0, -0.25, -0.5 and -0.1 MPa. Germination percentage, mean germination time, seedling fresh weight and vigour index, and radicle, hypocotyl and cotyledon lengths were determined. Seed germination and seedling development decreased in all taxa in the presence of PEG and NaCl, in a concentration-dependent manner, although the effect of salt was stronger than that of PEG, at the same osmotic potentials. Germination and seedling parameters varied for the different accessions but, in practical terms, considering only the final germination percentages under stress, P. halimoides L. appears to be the taxon most tolerant to water deficit, whereas P. grandiflora Hook. would be the most tolerant to salt stress..

[EN] This study assessed the responses of four local Spanish cultivars of Phaseolus lunatus (lima bean) to moderate salinity. For three weeks, plants were exposed to increasing salinity (50-150 mM NaCl) under greenhouse conditions. At the end of the experiment, several growth and biochemical parameters were determined. Salt stress reduced the fresh weight of aerial organs, allowing us to rank the four genotypes according to their tolerance to salinity. The concentration of most photosynthetic pigments remained unaltered, except carotenoids that were reduced in the least salt-tolerant cv. (cultivar) VPH-79. Leaf Na+ and Cl- concentrations increased with increased salt concentration of irrigation water, but K+ either remained constant, as in the most tolerant 'BGV-15410', or increased in the other cultivars, resulting in an unchanged K+/Na+ ratio under stress in two of the selected cultivars. Moreover, proline increased in all cultivars, most notably in cv. VPH-79, with the highest absolute concentrations registered in the more salt tolerant cultivars. Interestingly, these cultivars already had a relatively higher proline concentration in non-stressed plants. These findings indicate that P. lunatus is moderately salt tolerant and that its main mechanisms to adjust to salinity stress are the maintenance of high concentrations of K+ and proline accumulation in leaves.

[EN] Drought and soil salinity are at present the major factors responsible for the global reduction of crop yields, and the problem will become more severe in the coming decades because of climate change effects. The most promising strategy to achieve the increased agricultural production that will be required to meet food demands worldwide will be based on the enhancement of crop stress tolerance, by both, traditional breeding and genetic engineering. This, in turn, requires a deep understanding of the mechanisms of tolerance which, although based on a conserved set of basic responses, vary widely among plant species. Therefore, the use of different plant models to investigate these mechanisms appears to be a sensible approach. The genus Portulaca could be a suitable model to carry out these studies, as some of its taxa have been described as tolerant to drought and/or salinity. Information on relevant mechanisms of tolerance to salt and water stress can be obtained by correlating the activation of specific defence pathways with the relative stress resistance of the investigated species. Also, species of the genus could be economically attractive as `new¿ crops for `saline¿ and `arid¿, sustainable agriculture, as medicinal plants, highly nutritious vegetable crops and ornamentals.

[EN] Larix decidua, the European larch, is not normally affected by drought or salinity in its natural habitats, but it may be when grown as an ornamental tree, by the widespread practice of winter de-icing of mountain roads with NaCl, and because of global warming-induced environmental changes. The responses of two-month-old larch seedlings to 30 days water deficit (withholding irrigation) or salt stress (150 mM NaCl) treatments were studied by determining stress-induced changes in several growth parameters and biochemical markers (ion and osmolyte contents, level of oxidative stress, activation of enzymatic and non-enzymatic antioxidant systems). Both treatments caused the inhibition of growth, degradation of photosynthetic pigments, a small increase in malondialdehyde (MDA, an oxidative stress biomarker), and the activation of antioxidant enzymes: superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR). In all cases, salinity appeared to have stronger effects on the seedlings than water deficit. The presence of relatively high concentrations of glycine betaine, both in control and stressed plants, may represent a constitutive mechanism of defence against stress in European larch. Additionally, other responses were specific for salt stress and included the activation of K+ transport from roots to shoots and the accumulation of Pro as an osmoprotectant

[EN] Comparative analyses of the responses to abiotic stress in related taxa with different degrees of tolerance can provide useful information to elucidate the mechanisms of stress tolerance in plants. This kind of study has been carried out in four Silene species, which were subjected to salt and water deficit treatments under controlled greenhouse conditions. Growth parameters and leaf levels of photosynthetic pigments, ions, osmolytes, malondialdehyde (MDA, an oxidative stress biomarker), total phenolic compounds and flavonoids, were determined in control and stressed plants. The degree of stress-induced growth inhibition allowed establishing the relative tolerance of the studied species, identifying S. vulgaris as the most tolerant to salinity and S. sclerocarpa to water deficit; these data correlated well with the characteristics of their natural habitats. All four species showed a high resistance to stress-induced leaf dehydration, and a good negative correlation was found between tolerance and the degradation of photosynthetic pigments. Salinity tolerance is mostly based on the inhibition of Na+ transport to the leaves and the maintenance of relatively high leaf K+ levels in the salt-treated plants. Proline is a reliable stress biomarker but does not appear to be involved in tolerance mechanisms in this genus, as it accumulates at higher levels in the more sensitive species.MDA contents did not increase significantly in response to the stress treatments ¿ except in water-stressed S. latifolia, the species most affected by water deficit ¿ suggesting that the plants were not affected by secondary oxidative stress under the experimental conditions used. Accordingly, the measured variations in the levels of total phenolic compounds and flavonoids were not statistically significant or did not correlate with the relative stress resistance of the studied species. Therefore, stress responses based on the activation of antioxidant systems do not seem to be relevant f