Francisco Espinosa

Antimony (Sb) is a toxic metalloid whose presence in the environment has increased in recent years due to anthropogenic activities. In soils, this element may occur as the pentavalent ion Sb(V) (antimonate) or the trivalent ion Sb(III). The latter is more abundant in nature and more harmful to living organisms. In this study, the effects of Sb(III) on a model plant of major agronomic interest – tomato – are investigated in order to elucidate which compounds or metabolic pathways may be key in the plant response to this stressor. In order to achieve this objective, tomato seedlings were cultivated hydroponically and exposed to varying concentrations of Sb(III). This approach ensured optimal availability of the metalloid to the plants. The results of the present study demonstrate that exposure to Sb(III) inhibits plant growth and triggers a range of defence mechanisms, among which proline, phytochelatins (PCs) and enzymes of the AsA/GSH cycle play a prominent role in xenobiotic detoxification. In particular, ascorbate peroxidase (APX), glutathione reductase (GR), dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase (MDHAR) exhibited significant increases in both content and activity, particularly in roots compared with shoots. In addition to biochemical activity, an assessment was conducted to determine whether the expression of genes encoding these enzymes, as well as those involved in the biosynthetic pathways of the related compounds, was affected. The results of this assessment indicated the same trend. The present study underlines the pivotal function of the AsA/GSH cycle in plant defence in the context of elevated Sb(III) exposure, proposing that roots function as a barrier to restrict the translocation of this metalloid to aerial tissues. These findings may contribute to the identification of species best suited to the remediation of Sb-contaminated environments, based on the enzymes and compounds that play central roles in the defensive response described here. Studies such as the present one contribute to advancing our understanding of the mechanisms by which plants can enhance their remediation capacity and safely restore environments contaminated by xenobiotic compounds.

Grapevine Trunk Diseases (GTDs) are caused by phytopathogenic fungi that compromise grapevine productivity and wine quality. Most GTDs preventive treatments are chemical-based and environmentally harmful. One goal of the European Green Deal is to develop sustainable agriculture which does not harm the environment and reduces pesticide use and an alternative to those treatments may be the use of elicitors such as oligosaccharides from fungi. Many studies confirm that oligosaccharides activate the defence response. The experiment was carried out in vineyards of Tempranillo and Airén cvs. Asymptomatic and symptomatic vines were treated with mannans. Leaves and grapes were taken and pigments and phenols content, polyphenol oxidase (PPO) and superoxide dismutase (SOD) activities and gene expression of several defence enzymes were determined. The mannan addition to symptomatic vines was more positive for the leaves than for the grapes, palliating the damage caused by the disease, especially in the cv. Tempranillo. On the one hand, in the leaves, mannans caused an increase in phenols and PPO activity and expression; on the other hand, in grapes, although phenols increased, the other parameters did not. Mannans increased the expression levels of chalcone synthase ( CHS1 , CHS3 ), phenylalanine ammonia lyase ( PAL ), SOD , and PPO in asymptomatic leaves of both cultivars. In symptomatic leaves, CHS3 and PAL expression decreased in both cultivars, while CHS1 and PPO increased only in Tempranillo. In grapes, the expression of the genes varied due to the development of the disease. The mannan treatment seemed to reduce the oxidative stress caused by GTDs, but, above all, mannans would act as a biostimulant activaing the defence system of asymptomatic vines that would help them respond more successfully to a possible pathogenic fungi infection, that although this response depended on the cultivar.

This study demonstrates that sunflower plants display integrated, multilevel responses to excessive lithium (Li) exposure. Li concentrations above 5 mM markedly impair germination, growth, and biomass accumulation. Li is preferentially accumulated in the shoots, showing high translocation and bioaccumulation factors, and disrupts mineral nutrient homeostasis, particularly potassium (K) and sodium (Na) uptake, while inducing oxidative stress. Although photosynthetic pigment contents decline, photosynthetic efficiency is largely maintained, except at 10 mM Li. Li treatment enhances superoxide anion (O₂^.−) and hydrogen peroxide (H₂O₂) production exclusively in leaves. Consequently, activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR), and glutathione reductase (GR) increase in leaves, whereas only APX and GR are stimulated in the roots. Nitric oxide (NO) accumulation is detected only in leaves, while hydrogen sulfide (H₂S) and glutathione (GSH) contents decline. Leaf ascorbate (AsA) levels decrease concomitantly with dehydroascorbate (DHA) accumulation. Expression analyses of catalase, DHAR, DHAR-like, and glutathione S-transferase (GST) genes confirm their involvement in Li stress responses. Moreover, global DNA methylation analyses reveal hypomethylation in leaves and hypermethylation in the roots. Overall, Li exposure induces dose- and organ-specific physiological, molecular, and epigenetic adjustments in sunflower plants under environmentally relevant concentrations and controlled experimental conditions in this study.

This article offers a comprehensive review of sustainable plant nutrition concepts, examining a multitude of cutting‐edge techniques that are revolutionizing the modern area. The review copes with the crucial role of biostimulants as products that stimulate plant nutrition processes, including their potential for biofertilization, followed by an exploration of the significance of micronutrients in plant health and growth. We then delve into strategies for enhancing plants' tolerance to mineral nutrient contaminants and the promising realm of biofortification to increase the essential nutrients necessary for human health. Furthermore, this work also provides a concise overview of the burgeoning field of nanotechnologies in fertilization, while the integration of circular economy principles underscores the importance of sustainable resource management. Then, with examined the interrelation between micronutrients. We conclude with the future challenges and opportunities that lie ahead in the pursuit of more sustainable and resilient plant systems.

Processing tomato is one of the most important crops in Extremadura region, Spain, since the largest national agricultural production and first industrial processing of this sector is concentrated in this area. In these two production stages, greenhouse gases (GHGs) are emitted, but there is also a capture of atmospheric carbon dioxide (CO₂) by the plants and therefore, this study focuses on assessing the carbon balance of this activity in this specific crop area. In this work, the amount of CO₂ fixed by tomato plants is evaluated, bearing in mind the production area and tomato cultivars. Subsequently, the carbon footprint is calculated, and finally, the carbon balance is established for each location. Under the conditions of this study, each processing tomato plant annually fixes 0.6090 kg of CO₂, and each kilogram of tomato produced allows 0.1905 kg of CO₂ to be captured. In contrast, GHG emissions average 0.0338 kg CO₂ equivalent; therefore, the carbon balance is clearly positive. Even adding the emissions from the industry to those from farming, the carbon balance of this activity is clearly positive (0.0900 kg CO₂ captured for each kg of tomato processed), indicating that processing tomato crops in this area of Spain could more than compensate for the emissions produced.

Currently, there is an increasing presence of heavy metals and metalloids in soils and water due to anthropogenic activities. However, the biggest problem caused by this increase is the difficulty in recycling these elements and their high permanence in soils. There are plants with great capacity to assimilate these elements or make them less accessible to other organisms. We analyzed the behavior of Solanum lycopersicum L., a crop with great agronomic interest, under the stress caused by antimony (Sb). We evaluated the antioxidant response throughout different exposure times to the metalloid. Our results showed that the enzymes involved in the AsA-GSH cycle show changes in their expression level under the stress caused by Sb but could not find a relationship between the NITROSOGLUTATHIONE REDUCTASE (GSNOR) expression data and nitric oxide (NO) content in tomato roots exposed to Sb. We hypothesize that a better understanding of how these enzymes work could be key to develop more tolerant varieties to this kind of abiotic stress and could explain a greater or lesser phytoremediation capacity. Moreover, we deepened our knowledge about Glutathione S-transferase (GST) and Glutathione Reductase (GR) due to their involvement in the elimination of the xenobiotic component.

Grapevine Trunk Diseases (GTDs) are caused by a wide variety of phytopathogenic fungal species that compromise grapevine productivity and wine quality. Each year they lead to major economic losses. Most GTD treatments currently available on the market are chemical-based and environ-mentally harmful. Given that one of the goals proposed by the European Green Deal is to develop sustainable agriculture which does not harm the environment, reduces pesticide use, and pro-motes rural area economies, an alternative to those treatments may be the use of elicitors such as oligosaccharides from fungal organisms. Indeed, many studies have confirmed that oligosaccha-rides play important roles in activating plants' innate immunity. Mannans are one possible type of such oligosaccharides. The present work analysed Vitis vinifera L. (cv. Tempranillo and cv. Airén) leaves and grapes to evaluate their physiological and molecular response to GTDs and how this response might be conditioned using different concentrations of mannans as elicitors. It was found that mannan addition to diseased vines was more positive for the leaves than for the grapes. In general, mannans increased the expression levels of chalcone synthase (CHS1, CHS3), phenylalanine ammonia lyase (PAL), superoxide dismutase (SOD), and polyphenol oxidase (PPO) in healthy leaves of both varieties. In diseased leaves, CHS3 and PAL decreased in both varieties, while CHS1 and PPO increased in Tempranillo but not in Airén. In the grapes, the expression pat-terns of the genes studied varied greatly due to the development of the disease. The mannan treatment seemed to reduce the oxidative stress caused by GTDs, although this response depend-ed on the variety and on the plant's phytosanitary status.

Dittrichia plants were exposed to thallium (Tl) stress (10, 50, and 100 µM) for 7 days. The Tl toxicity altered the absorption and accumulation of other nutrients. In both the roots and the leaves, there was a decline in K, Mg, and Fe content, but an increase in Ca, Mn, and Zn. Chlorophylls decreased, as did the photosynthetic efficiency, while carotenoids increased. Oxidative stress in the roots was reflected in increased lipid peroxidation. There was more production of superoxide (O₂^.−), hydrogen peroxide (H₂O₂), and nitric oxide (NO) in the roots than in the leaves, with increases in both organs in response to Tl toxicity, except for O₂^.− production in the roots, which fluctuated. There was increased hydrogen sulfide (H₂S) production, especially in the leaves. Superoxide dismutase (SOD), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR), and glutathione reductase (GR) showed increased activities, except for APX and MDHAR in the roots and GR in the leaves. The components of the ascorbate–glutathione cycle were affected. Thus, ascorbate (AsA) increased, while dehydroascorbate (DHA), reduced glutathione (GSH), and oxidized glutathione (GSSG) decreased, except for in the roots at 100 µM Tl, which showed increased GSH. These Tl toxicity-induced alterations modify the AsA/DHA and GSH/GSSG redox status. The NO and H₂S interaction may act by activating the antioxidant system. The effects of Tl could be related to its strong affinity for binding with -SH groups, thus altering the functionality of proteins and the cellular redox state.

Esca is a multi-fungal disease affecting grapevines. The objective of the study was to evaluate the physiological and molecular response of the grapevine cv. Tempranillo to esca disease, carried out in a vineyard under Mediterranean climatic conditions in western Spain. The photosynthetic pigments in the leaves decreased, with a strong decrease in the photosynthetic efficiency. The proline content increased significantly in the early stages of affected leaves, being possibly involved in the maintenance of lipid peroxidation levels in leaves, which do not increase. The phenol, flavonoid, and phenylpropanoid content decreased in esca-affected leaves, as does the total antioxidant capacity (FRAP), while the polyphenol oxidase (PPO) activity suffers a strong increase with the development of the disease. In affected grapes, the lipid peroxidation and the total phenol content decrease, but not the anthocyanin content. The ascorbate pool decreases with the disease and with time. On the other hand, pool GSH + GSSG is lower in affected leaves, but increases with time. These alterations show a clear change in the redox homeostasis. The expression of genes phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), superoxide dismutase (SOD), and chalcone synthase (ChaS1 and ChaS3) become considerably higher in response to esca, being even higher when the infection time increases. The alteration of AsA and GSH levels, phenolic compounds, PPO activity, proline content, and FRAP, together with the increase of the PAL, PPO, SOD,ChaS1, and ChaS3 gene expression, are clearly implicated in the esca response in plants. The expression of these genes, similar to the PPO activity, can be used as markers of state in the development of the disease.

The objective of this work was to analyse, using a time series analysis, the effect of water regime for two cultivars at three stages of ripeness, during three consecutive years. Fruit and oil yield; O₂⁻ production and NADH oxidation activities; polyphenol oxidase (PPO), superoxide dismutase (SOD) and peroxidase (POX) activities; total phenols, flavonoid and phenylpropanoid glycoside content; and total antioxidant capacity (FRAP) were determined. All these parameters were found to depend on variety, irrigation and year. The results showed that the fruit and oil yields were strongly dependent on both irrigation and variety. The DW/FW ratio was practically constant during ripening, with small variety-dependent changes due to irrigation. Total amino acid and protein contents increased with ripening, with a close dependence on variety but not on irrigation. The SOD and POX activities appeared closely related, and related to the NADH oxidation and the amount of O₂⁻. The evolution of phenols and FRAP during ripening was complementary to that of NADH oxidation, O₂⁻ production as well as SOD and POX activities. The determining factors of the SOD, POX and PPO activities were the variety and the ripening; the determining factor of the yield, ROS production, total phenols and antioxidant capacity was the water regime. Inverse correlations were observed between maximum temperature and total phenols (−0.869), total flavonoids (−0.823), total PPGs (−0.801) and FRAP (−0.829); and between DW/FW and irrigation (−0.483). The remaining significant correlations were positive.