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Introduction: The reduction of N supplied combined with the use of biostimulants can be an efficient strategy that allows sustainable agriculture to achieve better economic, nutritional and environmental goals without reducing production. Moreover, the industrial processing of celery generates large amounts of waste. Therefore the purpose of this study was improve crop management strategies to reduce nitrate pollution while turning crop waste into value-added products for others sectors., Methods: Consequently, in this work twelve treatments were examined: three N nitrogen content in the nutrient solution (100% control, 60%, and 30%) combined with the inoculation of the roots with Azotobacter salinestris , and foliar application selenium solution (8 μM, Na 2 SeO 4 ). The celery parts from plants grown under limited N dose showed a higher antioxidant activity and TPC (total phenolic compounds) content., Results and Discussion: The antioxidant activity increased 28% in leaves and 41% in by-products and TPC improved 27% in leaves and 191% in by-products respect to the control. Besides, a significant reduction of β-carotene content (56%, 11% and 43% in petioles, leaves and by-products respect to the control, respectively) was obtained in plants fed with restricted dose of N. The catalase activity was not affected by N dose. The inoculation of the plants with Azotobacter , together with a reduced N dose, achieved a greater accumulation of all the parameters studied. This accumulation was maximum when Se was applied to the leaves compared with the control and depending on the celery part: TPC (121-450%); antioxidant activity (60-68%), of catalase activity (59% - 158%), and of pigments content (50-90%). These findings can boost the valorization of celery by-products as excellent source of bioactive compounds., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Collado-González, Piñero, Otálora, López-Marín and del Amor.)

Due to climate change and exacerbated population growth, the search for new sustainable strategies that allow for greater food productivity and that provide greater nutritional quality has become imperative. One strategy for addressing this problem is the combined use of fertilization with a reduced dose of nitrogen and biostimulants. Celery processing produces a large amount of waste with its concomitant pollution. Therefore, it is necessary to address the valorization of its byproducts. Our results revealed reductions in the biomass, Na, P, Mn, B, sugars, and proteins in the byproducts and increased lipid peroxidation, Fe (all celery parts), and K (byproducts) when the N supplied was reduced. Plants inoculated with Azotobacter salinestris obtained a greater biomass, a higher accumulation of K (byproducts), a build-up of sugars and proteins, reduced concentrations of P, Cu, Mn, B, Fe (petioles), and Zn (byproducts), and reduced lipid peroxidation. The application of Se at 8 μM reinforced the beneficial effect obtained after inoculation with Azotobacter salinestris . In accordance with our results, edible celery parts are recommended as an essential ingredient in the daily diet. Furthermore, the valorization of celery byproducts with health-promoting purposes should be considered.

The use of nitrogen as a fertilizer can be highly risky when used excessively, and it is therefore necessary to find novel techniques to reduce its use. Aquaponics reduces the use of synthetic fertilizers and water, and the leaching of nitrate into the environment. One way to avoid problems due to a reduction in nitrogen availability could be the use of plant growth promoting rhizobacteria (PGPR). This study examines the effect of PGPR on kohlrabi plants grown with a traditional nutrient solution (100S), in combination with "fish water" (50F/50D), or with a supplement of synthetic fertilizers (50F/50D + S). Two formulations were used: T1 ( Azospirillum brasilense and Pantoea dispersa ) and T2 ( Azotobacter salinestris ). Irrigation with 50F/50D caused a reduction in several of the measured parameters. The combined application of 50F/50D with T1 attenuated the negative effects. T2 did not present significant effects on the parameters measured. The results obtained with 50F/50D + S hardly showed differences with the 100S. Thus, by irrigating with 50F/50D + S, we were able to maintain the yields while reducing fertilizer use and water. The combined use of T1 and 50F/50D was also positive; however, it would be necessary to continue adjusting the amount of nitrate supplied to maintain production.

Heat and nutritional stresses have a significantly effect on the accumulation of bioactive and other compounds harmful to human health, like nitrates, in green leafy vegetables like lamb's lettuce. Plant growth-promoting bacteria (PGPB) have shown to confer beneficial biochemical changes to various crops under different stresses. The hypothesis proposed here is that the combination of optimal N level (2.5 Mm, 12 mM or 20 mM of N) with the inoculation of PGPB in plants exposed to heat shock (43 °C) may be a good strategy to obtain healthier lamb's lettuce with a higher yield. Results showed that a dose of 20 mM N can be considered as overfertilization. Moreover, the inoculation of plants fed with fertilizers with reduced N and under heat stress, resulted in higher productivity and content of sugars (60 %), amino acids (94 %), nitrogen (21 %), and total phenolic compounds (30 %), and a reduced content of nitrates (27 %)., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

In recent years, the interest on baby-leaf lettuce has grown steadily, because it is richer in bioactive compounds than other traditional vegetables. However, the quality of lettuce is being increasingly affected by climate change. It is very rare for a climatic effect to occur in isolation. Even then, a large body of work has only focused on the effect of isolated heat stress, fertilization, and elevated CO2, on morphological, physiological and biochemical parameters. Thus, very few works have focused on how the combination of several of these factors can affect these parameters. For first time, the present work studied the combined effect derived from the application of two different levels of CO2 (400 and 1000 ppm of CO2), four different NO3-/ NH4+ ratios (100/0 (T-I), 100/0 before the short-term heat stress and finally without NO3- (T-II), 80/20 (T-III) and 50/50 (T-IV)), and a short-term heat stress (25 and 43°C), on some physiological and quality parameters (dry biomass, photosynthetic parameters, pigments content, lipid peroxidation and total soluble proteins content) of baby-leaf lettuce cv Derbi. Additionally, a comparison of that combined effect of all these parameters between inner and outer leaves was also performed. The results obtained indicated that the interaction between the nutrient solution containing a 50/50 NO3-/ NH4+ ratio and a high concentration of CO2 (1000 ppm) improved the biomass, photosynthesis, intercellular/external CO2 concentration ratio (ci/ca), stomatal conductance (gs), evapotranspiration (E) and lipid peroxidation, and protein content in this baby-leaf lettuce. The results obtained in this work lead us to conclude that this existing interaction between the NO3-/ NH4+ ratio and the elevated CO2 concentration may be considered as a new strategy for making baby-leaf lettuce more resistant to heat stress, in other words, stronger against the ever more frequent heat waves., Competing Interests: The authors declare that no competing interests exist in this work., (Copyright: © 2022 Collado-González et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

To improve water and nutrient use efficiencies some strategies have been proposed, such as the use of mulching techniques or arbuscular mycorrhizal fungi (AMF) inoculation. To gain insights into the interaction between the use of hydromulch and AMF inoculation on plant growth and productivity, escarole plants ( Cichorium endivia , L.) were inoculated with the AMF Rhizophagus irregularis and grown with non-inoculated plants under different soil cover treatments: ecological hydromulching based on the substrate of mushroom cultivation (MS), low-density black polyethylene (PE), and non-covered soil (BS). AMF inoculation or the use of mulching alone, but especially their interaction, increased the plant growth. The growth improvement observed in AMF-inoculated escarole plants grown under hydromulching conditions was mainly associated with the upgrading of nitrogen and phosphorous use efficiency through the regulation of the hormonal balance. Both hydromulching and AMF inoculation were found to increase the active gibberellins (GAs) and cytokinins (CKs), resulting in a positive correlation between these hormones and the growth-related parameters. In contrast, the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) and abscisic acid (ABA) decreased in AMF-inoculated plants and especially in those grown with the MS treatment. This study demonstrates that there exists a positive interaction between AMF and hydromulching which enhances the growth of escarole plants by improving nutrient use efficiency and hormonal balance.

Frequency, intensity and duration heat-related events have profound implications for future food supply through effects on plant growth and development. This concern needs effective and urgent mitigation tools. However, the effectiveness of potential solutions may decrease according to the specific cultivar response rather consider at specie level. The metyl-jasmonates are essential cellular regulators which are involved in pivotal plant development processes and related to confer protection to heat shock. Thus, our aim was to study the response of three pepper cultivars, Agio (Hungarian type), Basque (Chilli type), and Loreto (Lamuyo type), subjected to heat shock (40°C/72 h) and foliarly-sprayed with methyl-jasmonate (MeJA; 100 µmol), and the effects on several physiological traits. Our results show that despite the important differential impact of heat shock caused on each cultivar, MeJA application did not affect gas exchange, chlorophyll A concentration or efficiency of the photosystem in these cultivars. However, P concentration was reduced when MeJA was applied to Basque chilli, and a significant effect on leaf carbohydrates concentration was observed for Agio and Loreto. Moreover, Agio was the only cultivar in which the amino-acid profile was affected by MeJA under heat shock. Under that condition, putrescine increased for all cultivars, whist the effect of MeJA was only observed for spermine and histamine for Agio and Loreto. Thus, the results indicated that the ameliorative impact of MeJA on this stressor was clearly influenced by cultivar, revealing specific traits. Thus, these results could be used as valuable tools for the characterization of this intraspecific tolerance to heat shock during the vegetative growth stage of pepper., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest, (Copyright © 2022 Otálora, Piñero, Collado-González, Gálvez, López-Marín and del Amor.)

The isolated effects of heat stress, fertilization and elevated CO 2 on the content of several health-promoting compounds in plants have been quite studied. However, few studies have focused on two of these three factors together. This work provides information on how two different levels of CO 2 , four different NO 3 - /NH 4 + ratios in the nutrient solution, and a short-term heat stress affect the biomass and nutritional quality of baby-leaf lettuce cv Derbi. Furthermore, the nutritional quality of the inner and outer leaves was also studied and compared. Results indicated that the strategy used led to a bigger and healthier baby-leaf lettuces. So, this lettuces contained a higher content of sugars, minerals and phenolic compounds and showed an enhanced antioxidant activity. On the other hand, results exhibited that whilst in inner leaves the biosynthesis of antioxidant compounds were favored, in outer leaves was favored the biosynthesis of sugars and mineral content., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Se has beneficial effects on plants, through the stimulation of plant productivity, the reduction of abiotic stresses, and the improvement in N metabolism. Therefore, we investigated the effect of the foliar application of different concentrations of Se (0, 4, 8 and 16 μmol L -1 ) on lettuce plants grown in an aquaponics system (fish water) compared with a control (conventional soilless fertigation). The NO 3 - concentration supplied by the fish water was 47% of the control solution. The results showed a reduction in the fresh weight of lettuce plants irrigated with the fish water mixture treatment, along with an increase in sugar concentration. However, the application of Se at 4 and 16 μmol L -1 , prompted a relief of this stress, reducing both lipid peroxidation and the sugar content, and increasing the nitrate concentration. In addition, in the case of the highest concentration of Se (16 μmol L -1 ), the values of nitrate were comparable those control plants. We show the importance of sprayed Se in increasing the efficiency of N utilization, in addition to lessening environmental issues for aquaponics culture., (Copyright © 2022 Elsevier Masson SAS. All rights reserved.)

In order to mitigate the detrimental impact that climate change is having on plants, the study of new practices that allow for the reduction of such effects has become imperative. In addition, the revaluation of the promotion of healthy plant by-products has also markedly increased in importance in recent years. In this work, the modifications in biomass and some antioxidant compounds of cauliflower by-products treated with putrescine under extreme temperatures in two different CO 2 scenarios (the control (400 ppm) and a high concentration of CO 2 (1000 ppm)) were studied. Additionally, the compositions of inner and outer leaves were also compared. According to results found in this work, cauliflower grown under elevated CO 2 and treated with putrescine (2.5 mM) prior to heat stress showed the highest biomass accumulation (20%) compared to the control. Moreover, in the outer leaves from cauliflower grown under elevated CO 2 and treated with putrescine prior to high temperature exposure, the highest biosynthesis of sugars (20%) was recorded. Although cauliflower by-products turned out to be rich in polyamines (208.6 nmoles g -1 fresh weight (FW) and 124.3 nmoles g -1 FW for outer and inner leaves, respectively) and phenolic compounds (1070.2 mg gallic acid equivalents ( (GAE) 100 g -1 FW in outer leaves and 772.0 mg GAE 100 g -1 FW in inner leaves), it was the outer leaves that after applying the new strategy showed the greatest increase in polyamines (68%) and phenolic compounds (39%), obtaining here the highest increase in antioxidant activity (3%). Thus, they should no longer be regarded as mere by-products and should be used for pharmaceutical or nutraceutical purposes. The novel strategy presented in this work may allow us to take advantage of both the continued increase in CO 2 and heat waves that are becoming more frequent.

Background: Environmental conditions affect the quality of the fruits and their organoleptic properties. In low-tech greenhouses, these environmental conditions are frequently not optimal for crops. Therefore, the present study demonstrates the effects of the use of an integrated passive heating and cooling system in a greenhouse located in the Mediterranean area on the quality of pepper fruits., Results: The results indicate that the passive system utilized (i) improved many parameters, such as average weight of fruits, °Brix, glucose and fructose content, and P and K content; (ii) increased the values of b* and h ab *; and (iii) reduced total phenolic compounds, total amino acids content, and Fe and Zn content. However, the degree of the effect of the climatic factors on these parameters was also affected by harvest time., Conclusion: This novel study highlights the possibility of improving the nutritional quality of pepper fruits by modifying the environmental conditions through the use of passive heating and cooling systems at the same time as reducing the carbon footprint. © 2021 Society of Chemical Industry., (© 2021 Society of Chemical Industry.)

In the last years, the atmospheric CO 2 concentration has increased significantly, and this increase can cause changes in various physiological and biochemical processes of plants. However, the response of plants to elevated CO 2 concentration (e[CO 2 ]) will be different depending on the nitrogen form available and the plant species. Therefore, hydroponic trials on cucumber plants, with two CO 2 concentrations (400 and 1000 ppm) and two nitrogen sources (NO 3 - /NH 4 + ; 100/0 and 90/10), were conducted. Physiological parameters-such as gas exchange, GS, GOGAT and GDH activities, cation composition, soluble sugar and starch content- were measured. The results showed that when plants were grown with NH 4 + and e[CO 2 ], parameters such as photosynthesis rate (A CO2 ), instantaneous water use efficiency (WUEi), the content of NH 4 + , Ca 2+ and Mg 2+ , and the concentration of starch, were higher than in control plants (irrigated with nitrate as sole nitrogen source and ambient CO 2 concentration (a[CO 2 ])). Furthermore, an improvement in N assimilation was observed when the GS/GOGAT pathway was enhanced under these conditions (NH 4 + and e[CO 2 ]). Thus, our results contribute to the reduction of the negative environmental impacts of the use of nitrogen fertilizers on this crop, both by reducing nitrogen leakage (eutrophication) and greenhouse gas emissions., (© 2021. The Author(s).)