Agricultural uses of plant biostimulants

A sensitive electrochemical DNA biosensor for detecting the genome of a plant growth-promoting bacteria

The challenge of increasing food production while maintaining environmental sustainability can be addressed by using biofertilizers such as Azospirillum, which can enhance plant growth and colonize more than 100 plant species. The success of this biotechnology depends on the amount of plant growth-promoting bacteria associated with the plant during crop development. However, monitoring bacterial population dynamics after inoculation requires time-consuming, laborious, and costly procedures. To address these issues, this study describes an effective electrochemical DNA biosensor to detect Azospirillum brasilense. The biosensor comprises a glassy carbon electrode modified with a nanocomposite based on carbon nanotubes and gold nanoparticles capped with 3-n-propylpyridinium chloride silsesquioxane, followed by the immobilization of a thiolated probe oligonucleotide that binds specifically to the A. brasilense genome (AZOgenome). The nanocomposite was characterized utilizing spectroscopic and morphological methods. Its presence on the biosensor's surface enhanced electrochemical responses due to its excellent electrocatalytic properties, as observed during electrochemical impedance spectroscopy and cyclic voltammetry experiments. The biosensor enabled the detection of AZOgenome after the hybridization event, which alters the electrochemical response of the electrode and was rapidly detected by square wave voltammetry. The detection range of the bacterial genome was 1.17 pmol L-1 to 146.8 pmol L-1, with LOD and LOQ of 0.261 and 0.322 pmol L-1, respectively, and sensitivity of -15.560 μA/log [AZOgenome] (pmol L-1). The biosensor showed good selectivity and reproducibility, with a coefficient of variation of -5.69 %, in addition to satisfactory sensitivity and stability for up to seven weeks. These promising analytical features allowed the quantification of A. brasilense in low concentrations in soil metagenomic DNA samples.

Integrated biorefinery process for dual production of fermentable sugars and functional humic acids from lignocellulose

In traditional lignocellulosic biorefineries, lignocellulose undergoes pretreatment followed by enzymatic hydrolysis to produce fermentable sugars, often leaving behind lignin rich residual biomass underutilized. In this study, we present a novel and integrated approach for the comprehensive utilization of lignocellulosic biomass as fermentable sugars and functional humic acids. First, corn stover was subjected to a mild densification pretreatment with Ca(OH)₂ (DLCA(ch)), facilitating efficient enzymatic hydrolysis and yielding 172.09 g/L of sugars at 30 % solid loading. Further, the enzymatic hydrolysis residues were subsequently converted into artificial humic acid (AHA) through a mild artificial humification process at 50 °C, catalyzed by potassium hydroxide (KOH) alone or in combination with urea. This process achieved a high AHA yield of 44.17 %, with a final concentration of 78 g/L. The AHA synthesized with KOH and urea (KU-AHA) predominantly consisted of medium molecular weight fractions (30-100 kDa) and exhibited enhanced nitrogen incorporation due to the involvement of urea. Additionally, KU-AHA demonstrated comparable effectiveness to natural humic acid in promoting plant growth, leading to an 13.40 % increase in plant height, an 11.82 % increase in root length. This integrated approach not only maximizes the utilization of lignocellulosic biomass but also provides a sustainable and efficient pathway for residue valorization.

Exploring the potential of lipid elicitors to enhance plant immunity

Lipids besides being components of membranes and storage molecules are also involved in signalling processes and have proven to be vital components in plant defence mechanisms. Over the past decades, the intricate lipid-signalling pathways that underlie the establishment of defence responses have been extensively studied. These molecules can act directly as signalling agents in plant defence or serve as precursors in a plethora of biosynthetic pathways, leading to the production of phytohormones and other signalling agents. Lipids have proven to be promising elicitors by not only trigger a robust and appropriate defence response, across various plant species, but also induce resistance against a wide range of pathogens. Allied to this, lipids are widespread molecules in nature, which makes them an accessible resource and highlights their potential use as a sustainable approach to crop protection. This comprehensive review emphasizes the potential of lipids and lipid-derived molecules as elicitors in developing sustainable agricultural practices. By leveraging the natural defence mechanisms of plants, lipid elicitors offer a viable and eco-friendly alternative to conventional pest management strategies, contributing to the overall goal of sustainable agriculture.

Organic Fertilization and Biostimulant Application to Improve Yield and Quality of Eggplant While Reducing the Environmental Impact

Environmental sustainability is a crucial issue in modern agriculture and special attention needs to be paid to soil health preservation. Eggplant (Solanum melongena L.) cultivation implies the supply of relevant quantities of chemical fertilizers, since the crop has high nutrient requirements. This study investigated the combined effects of two common organic amendments-compost and digestate-and two types of biostimulant-a plant-based product and a microbe-based product-on fruit production and quality of eggplant, to highlight the potential synergistic effects of fertilization and biostimulation. The experiment was carried out in a Mediterranean greenhouse in the winter/spring period, assessing early and total marketable yield and fruit qualitative traits (firmness, color, nitrogen, ascorbic acid, carotenoid and phenol content, and antioxidant activity). Results showed that the fertilization strategy significantly influenced plant productivity, with digestate promoting the early fruitification and mineral fertilizers resulting in a higher total yield. Biostimulants, particularly the microbial type, improved the fruit quality in terms of carotenoid content and antioxidant activity. These findings highlight the potential benefits of combining organic amendments with biostimulants in eggplant cultivation, enhancing the economic value of the product through the increase in the early production and fruit nutraceutical value while realizing sustainable practices.

Arginine and Spermine Ameliorate Water Deficit Stress in Fenugreek (Trigonella foenum-graecum L.) by Enhancing Growth and Physio-Biochemical Processes

Plants face various stresses, particularly water deficit, which negatively impacts photosynthesis, growth, and development, thereby limiting agricultural production. Utilizing growth regulators, such as amino acids and polyamines, to enhance osmotic stress tolerance is a crucial area of research in sustainable agriculture. This study investigates the impact of arginine and spermine treatments on various growth attributes, enzymatic and non-enzymatic antioxidants, photosynthetic pigments, protein and lipid peroxidation, and yield traits of fenugreek plants under both normal and drought conditions. The results indicate that drought conditions significantly reduce morphological characteristics, leaf pigments, and yield traits. However, the application of arginine and spermine enhances these parameters, with spermine showing a more pronounced effect. Additionally, treatments boost antioxidant enzymes activities and improve the levels of non-enzymatic antioxidants and osmolytes, contributing to better stress tolerance and growth performance. Principal component analysis confirms that drought significantly alters plant physiology, increasing proline and malondialdehyde levels, while arginine and spermine alleviate drought stress by enhancing antioxidant activity and osmolyte accumulation. The current investigation aims to evaluate the effectiveness of spermine and arginine treatments on various growth attributes and stress tolerance of fenugreek plants under normal and drought conditions, focusing on their comparative efficacy.

Unraveling the role of κ-carrageenan on the combined effect of drought and chromium stress in wheat (Triticum aestivium L.)

Drought (D) and chromium (Cr) stress co-occur in agricultural fields due to the accumulation of excessive Cr in soils from industrial pollution and increasing frequency of water scarcity. Carrageenan (Car), a compound extracted from red seaweed, is an emerging biostimulant with multifaceted roles in plants. This study investigated the role of exogenous Car in mediating tolerance to D-, Cr-, and DCr-stress in wheat seedlings, aiming to elucidate the potential of Car in mitigating toxicity and promoting plant resilience. Wheat seedlings exposed to DCr-stress exhibited reduced growth and biomass production, along with elevated levels of reactive oxygen, carbonyl, and nitrogen species. Moreover, D-stress exacerbated Cr-toxicity, as demonstrated by principal component analysis (PCA), which showed a strong positive correlation between DCr-stress and stress marker parameters. This suggests that DCr-stress resulted in higher Cr uptake and increased oxidative damage compared to individual D- or Cr-stress, making DCr-stress more detrimental than either stress applied alone. However, Car priming ameliorated the toxic effects of DCr-stress and promoted the growth performance of DCr-stressed wheat seedlings. In PCA, the positive correlation of D + Car, Cr + Car, and DCr + Car treatments with growth and plant defense-related parameters suggests that Car-mediated improvement in stress tolerance can be attributed to reduced accumulation of toxic Cr, increased levels of total free amino acids and soluble sugars, enhanced antioxidant enzyme activity, elevated non-enzymatic antioxidant levels, higher phenolic and flavonoid content, and improved metal chelation and detoxification. Our results indicated Car is a potential and cost-effective biostimulant for managing D-, Cr-, or DCr-stress in wheat.

Enhancing Yield, Physiological, and Quality Traits of Strawberry Cultivated Under Organic Management by Applying Different Non-Microbial Biostimulants

Organic farming is an environmentally friendly management practice that excludes the use of synthetic inputs, but at the same time is associated with lower yields than conventional production. In an attempt to compensate for yield reduction, resulting from foregoing the use of synthetic fertilizers, we hypothesized that the use of biostimulant products could provide much-desired food security. In light of this, a greenhouse experiment was conducted to compare and evaluate the effects of the foliar application of three different non-microbial biostimulants (a seaweed extract, a plant protein hydrolysate, and a plant extract) on the yield, mineral profile, and physiological response of strawberry (Fragaria × ananassa Duch.) grown in an organic farming context. Regardless of the type of biostimulant, treated plants showed significant improvement in photosynthetic performance. Specifically, the application of plant-derived protein hydrolysate increased ACO2 by 34.5% compared with control. Despite this, only the application of plant-derived protein hydrolysate significantly increased fruit yield per unit area (+13.5%). The improved performance of plants treated with plant-derived protein hydrolysate was associated with an overall improvement in mineral profile (compared to control +49.4 and 33.0% in NO3- and Mg2+ concentration, respectively). In contrast, application of the seaweed biostimulant increased (+17.4%) fruit antioxidant activity (DPPH) compared with control plants. These results underscore how the diverse origins of non-microbial biostimulants are responsible for specific responses in crops that can be exploited by organic growers to increase productivity.

The impact of an amino acid-humus preparation on lawn boning value

The application of biostimulants in fertilisation has been shown to enhance plant metabolism, stimulate physiological processes, and mitigate adverse environmental and pathogenic stresses. This study, conducted at the Agricultural University of Krakow (2021-2023), evaluated the efficacy of a foliar amino acid preparation enriched with humic acids (L-Amino + ® Humus) on turf quality. Four experimental variants were established: an untreated control (Variant I) and three treated plots sprayed with the biostimulant at 1.0 (Variant II), 2.0 (Variant III), and 3.0 L ha-1 (Variant IV). Higher application rates (Variants III and IV) significantly improved aesthetic turf quality and reduced fungal disease incidence. Compared to the control, Variant IV (3.0 L ha-1) decreased snow mould (Microdochium nivale) infections by 8% and brown spot (Rhizoctonia solani) prevalence by 12%. Variant III (2.0 L ha-1) also demonstrated positive effects, with 6% and 8% reductions in snow mould and brown spot, respectively. Furthermore, the Normalized Difference Vegetation Index (NDVI) and leaf greenness index (SPAD) chlorophyll meter values increased by 6% and 8%, respectively, in Variant IV relative to the control, indicating enhanced leaf greenness and photosynthetic efficiency. Nutrient analysis revealed that Variants III and IV significantly elevated macro- and micronutrient concentrations (e.g., nitrogen, potassium, iron) in plant biomass compared to the control. In contrast, Variant II (1.0 L ha-1) showed no statistically significant improvements in nutrient content or disease resistance. These findings suggest that L-Amino + ® Humus at doses of 2.0-3.0 L ha-1 enhances turf quality, bolsters resistance to fungal pathogens, and improves nutrient assimilation. Lower doses (1.0 L ha-1), however, were ineffective under the tested conditions. The study underscores the dose-dependent efficacy of biostimulants in sustainable turf management.

Interactive effects of irrigation and fertilization on the growth and physiological characteristics of greenhouse tomatoes, Solanum lycopersicum L

Water scarcity in China poses a significant challenge for sustainable greenhouse tomato production, necessitating strategies that optimize water use without compromising yield. While previous studies have explored irrigation and fertilization separately, comprehensive research on their combined effects using soluble organic fertilizers in arid regions is lacking. This study evaluates the interactive effects of different irrigation levels and fertilizer application patterns on the growth, physiological characteristics, water use efficiency (WUE), nutrient uptake, nitrogen use efficiency (NUE), and yield of greenhouse tomatoes. A pot experiment was conducted with three irrigation levels: I1 (90-100% field capacity), I2 (72-80% field capacity), and I3 (54-60% field capacity), and four fertilizer treatments: C1 (combined soluble organic and chemical fertilizer), C2 (soluble chemical fertilizer only), C3 (sheep manure and chemical fertilizer), and C4 (soluble organic fertilizer only). Results showed that increased irrigation significantly enhanced plant height, stem diameter, leaf area, leaf SPAD value, dry matter accumulation, nitrogen uptake, and fruit yield. Among all treatments, I1C1 achieved the highest fruit yield under sufficient irrigation, whereas the I2C1 treatment maintained a relatively high yield while notably improving root-to-shoot ratio, WUE, and nitrogen uptake, indicating an optimal balance for water-limited conditions. These findings demonstrate that integrating appropriate irrigation levels with combined fertilizer application can effectively mitigate water scarcity impacts, optimizing water savings and resource use efficiency while sustaining greenhouse tomato production in arid regions.

Thymbra spicata extract and arbuscular mycorrhizae improved the morphophysiological traits, biochemical properties, and essential oil content and composition of Rosemary (Rosmarinus officinalis L.) under salinity stress

BACKGROUND

Enhancing the content of essential oils and valuable secondary metabolites is a primary goal for medicinal plant breeders. In this study, the effects of Thymbra spicata extract at concentrations of 0% (C), 10% (TS1), and 20% (TS2), along with mycorrhizal fungus (MF) biofertilizer at a rate of 50 g/2.5 kg of soil, were evaluated on the growth, photosynthetic pigments, relative water content (RWC), proline, protein, malondialdehyde (MDA), catalase (CAT), phenylalanine ammonia-lyase (PAL), and essential oil content and composition of Rosmarinus officinalis L. under varying salinity stress levels of 0 mM (S0), 100 mM (S1), and 200 mM (S2) NaCl. The experiment was conducted as a factorial study within a completely randomized design, with three replications.

RESULTS

As salinity stress increased, the yield and growth characteristics of the plants declined. However, the applied treatments effectively mitigated the negative effects of salinity. The highest chlorophyll a, b, and total chlorophyll contents were observed in the TS2 + MF treatment under nonsaline conditions. Under S2 salinity stress, carotenoid and anthocyanin contents increased by 38.29% and 11.11%, respectively, with the use of TS2 + MF. Under S1 stress conditions, the proline and soluble sugar content increased by 268% and 44%, respectively, in the MF treatment. Essential oil content was enhanced by 80.43% with the TS2 + MF treatment under S1 stress. Essential oil analysis showed significant increases in camphene (9.71%), β-pinene (43.75%), α-phellandrene (13.3%), geranyl acetate (156%), cineole (21.39%), and β-linalool (5.12%) in the TS2 + MF treatment compared to the control under S1 stress conditions.

CONCLUSIONS

Among all the treatments, the combined application of TS2 and MF proved to be the most effective in enhancing the morphophysiological and biochemical characteristics of rosemary plants. This treatment not only boosted the production of essential oils and secondary metabolites but also mitigated the detrimental effects of salinity stress. Therefore, it is recommended as a beneficial agricultural practice for improving the productivity and quality of rosemary plants under salinity stress.

Fulvic Acid, Amino Acids, and Vermicompost Enhanced Yield and Improved Nutrient Profile of Soilless Iceberg Lettuce

Soilless cultivation systems are sustainable innovations in modern agriculture, promoting high efficiency per unit area, supporting food sustainability, and addressing the growing demand for high-quality produce with minimal environmental impact. This study evaluates the effects of fulvic acid, amino acid, and vermicompost biostimulants on the growth, yield, and nutrient profile of soilless-grown iceberg lettuce (Lactuca sativa var. capitata) in floating culture under controlled glasshouse conditions. Two experiments were conducted to determine the most effective concentrations and combinations of biostimulants. In the first experiment, varying doses of fulvic acid (40 and 80 ppm), amino acid (75 and 100 ppm), and vermicompost (1 and 2 mL L-1) were tested alongside a control. Optimal doses were identified based on their positive effects on lettuce growth and yield. The second experiment examined combinations of fulvic acid, amino acid, and vermicompost extract compared to a control. Biostimulants improved lettuce growth, nutrient uptake, and antioxidants. Vermicompost boosted root biomass and leaf area, while fulvic acid and amino acid reduced nitrates and increased dry matter. Fulvic acid and vermicompost resulted in the highest yield (17.15 kg/m2, 18.2% increase), and the combined treatment maximized antioxidants, increasing vitamin C by 17.16%, total phenols by 52.54%, and flavonoids by 52.38%. These findings highlight the potential of biostimulants as eco-friendly solutions for optimizing lettuce production in soilless systems.

Effect of two compost teas as inducers of tolerance to lead and aluminum on the initial growth of maize and sorghum

Compost teas have been reported to be inducers of tolerance to biotic and abiotic stresses in plants, but few studies have investigated heavy metal stress. We hypothesize that compost teas can mitigate the harmful effects of heavy metals in maize and sorghum. The objective of this work was to verify the effects of two compost teas, plant compost tea (PCT) and cattle manure compost tea (CMCT), as inducers of tolerance to lead (Pb) and aluminum (Al) in maize and sorghum. We produced and chemically analyzed the two compost teas and applied them to maize and sorghum exposed to Pb or Al to evaluate their effects on germination, initial growth, root morphology/architecture, antioxidant enzyme activity, and lipid peroxidation. In addition to stimulating and improving initial growth and root morphology/architecture, the two composts mitigated or nullified Pb and Al damage to several of the analyzed parameters, demonstrating biostimulant action. The effects observed are related to the chemical and microbiological composition of the compost teas, in addition to the increase in the enzymatic antioxidant metabolism of maize and sorghum.

Metabolic modeling identifies determinants of thermal growth responses in Arabidopsis thaliana

Temperature is a critical environmental factor affecting nearly all plant processes, including growth, development, and yield. Yet, despite decades of research, we lack the ability to predict plant performance at different temperatures, limiting the development of climate-resilient crops. Further, there is a pressing need to bridge the gap between the prediction of physiological and molecular traits to improve our understanding and manipulation of plant temperature responses. Here, we developed the first enzyme-constrained model of Arabidopsis thaliana's metabolism, facilitating predictions of growth-related phenotypes at different temperatures. We showed that the model can be employed for in silico identification of genes that affect plant growth at suboptimal growth temperature. Using mutant lines, we validated the genes predicted to affect plant growth, demonstrating the potential of metabolic modeling in accurately predicting plant thermal responses. The temperature-dependent enzyme-constrained metabolic model provides a template that can be used for developing sophisticated strategies to engineer climate-resilient crops.

Soil microbiome interventions for carbon sequestration and climate mitigation

Mitigating climate change in soil ecosystems involves complex plant and microbial processes regulating carbon pools and flows. Here, we advocate for the use of soil microbiome interventions to help increase soil carbon stocks and curb greenhouse gas emissions from managed soils. Direct interventions include the introduction of microbial strains, consortia, phage, and soil transplants, whereas indirect interventions include managing soil conditions or additives to modulate community composition or its activities. Approaches to increase soil carbon stocks using microbially catalyzed processes include increasing carbon inputs from plants, promoting soil organic matter (SOM) formation, and reducing SOM turnover and production of diverse greenhouse gases. Marginal or degraded soils may provide the greatest opportunities for enhancing global soil carbon stocks. Among the many knowledge gaps in this field, crucial gaps include the processes influencing the transformation of plant-derived soil carbon inputs into SOM and the identity of the microbes and microbial activities impacting this transformation. As a critical step forward, we encourage broadening the current widespread screening of potentially beneficial soil microorganisms to encompass functions relevant to stimulating soil carbon stocks. Moreover, in developing these interventions, we must consider the potential ecological ramifications and uncertainties, such as incurred by the widespread introduction of homogenous inoculants and consortia, and the need for site-specificity given the extreme variation among soil habitats. Incentivization and implementation at large spatial scales could effectively harness increases in soil carbon stocks, helping to mitigate the impacts of climate change.

A Study of the Different Strains of the Genus Azospirillum spp. on Increasing Productivity and Stress Resilience in Plants

One of the most important and essential components of sustainable agricultural production is biostimulants, which are emerging as a notable alternative of chemical-based products to mitigate soil contamination and environmental hazards. The most important modes of action of bacterial plant biostimulants on different plants are increasing disease resistance; activation of genes; production of chelating agents and organic acids; boosting quality through metabolome modulation; affecting the biosynthesis of phytochemicals; coordinating the activity of antioxidants and antioxidant enzymes; synthesis and accumulation of anthocyanins, vitamin C, and polyphenols; enhancing abiotic stress through cytokinin and abscisic acid (ABA) production; upregulation of stress-related genes; and the production of exopolysaccharides, secondary metabolites, and ACC deaminase. Azospirillum is a free-living bacterial genus which can promote the yield and growth of many species, with multiple modes of action which can vary on the basis of different climate and soil conditions. Different species of Bacillus spp. can increase the growth, yield, and biomass of plants by increasing the availability of nutrients; enhancing the solubilization and subsequent uptake of nutrients; synthesizing indole-3-acetic acid; fixing nitrogen; solubilizing phosphorus; promoting the production of phytohormones; enhancing the growth, production, and quality of fruits and crops via enhancing the production of carotenoids, flavonoids, phenols, and antioxidants; and increasing the synthesis of indoleacetic acid (IAA), gibberellins, siderophores, carotenoids, nitric oxide, and different cell surface components. The aim of this manuscript is to survey the effects of Azospirillum spp. and Bacillus spp. by presenting case studies and successful paradigms in several horticultural and agricultural plants.

Effects of vegetal protein hydrolysate application method, nitrogen level, and nitrate-to-ammonium ratio on growth and composition of hydroponic lettuce

BACKGROUND

Vegetal-derived protein hydrolysates (PHs) have been recognized as sustainable biostimulant products due to their beneficial effects on crops. However, most studies on PHs have been conducted at a fixed ratio of nitrate-to-ammonium (NO3 -:NH4 +) without considering other N application scenarios, leading to inconsistent results among the studies. This study compared the influences of N levels (2 or 10 mM N), NO3:NH4 ratios (100:0, 75:25, 50:50, or 25:75), and PH application methods - control, foliar spray (PH-F) or root application (PH-R) - on the yield, morphology, nutrients, and nutraceutical quality of hydroponic lettuce.

RESULTS

Nitrogen level, NO3:NH4 ratio, and PH application affected plant growth, morphology, and quality significantly, highlighting the importance of the interactions among these factors. Shoot growth was influenced by NO3:NH4 ratios, PH, and their interactions. Similar trends were observed in chlorophyll content. The interactions among all three factors significantly influenced root growth and morphology. Root application (PH-R) protected lettuce from yield loss caused by low NO3:NH4 ratios and from reduced antioxidant compounds caused by high N levels. Vegetal-derived protein hydrolysates improved nutrient uptake through two-way and three-way interactions although neither PH nor any interactions affected nitrate concentrations.

CONCLUSION

This study demonstrated that PH interacts with N level and NO3:NH4 ratio, affecting hydroponic lettuce yield and quality. In particular, the root application of PH was the most effective method for enhancing yield (shoot fresh weight), quality (chlorophylls, carotenoids, flavonoids, and phenols), and nutrient uptake in hydroponically grown lettuce in relation to N form and level. © 2024 Society of Chemical Industry.

Harnessing the plant microbiome for sustainable crop production

Global research on the plant microbiome has enhanced our understanding of the complex interactions between plants and microorganisms. The structure and functions of plant-associated microorganisms, as well as the genetic, biochemical, physical and metabolic factors that influence the beneficial traits of plant microbiota have also been intensively studied. Harnessing the plant microbiome has led to the development of various microbial applications to improve crop productivity in the face of a range of challenges, for example, climate change, abiotic and biotic stresses, and declining soil properties. Microorganisms, particularly nitrogen-fixing rhizobia as well as mycorrhizae and biocontrol agents, have been applied for decades to improve plant nutrition and health. Still, there are limitations regarding efficacy and consistency under field conditions. Also, the wealth of expanding knowledge on microbiome diversity, functions and interactions represents a huge source of information to exploit for new types of application. In this Review, we explore plant microbiome functions, mechanisms, assembly and types of interaction, and discuss current applications and their pitfalls. Furthermore, we elaborate on how the latest findings in plant microbiome research may lead to the development of new or more advanced applications. Finally, we discuss research gaps to fully leverage microbiome functions for sustainable plant production.

The soil application of a plant-derived protein hydrolysate speeds up selectively the ripening-specific processes in table grape

Plant-derived biostimulants have gained attention in agricultural practices for their potential to enhance crop quality and resilience. In this study, we investigated the effects of applying a maize gluten-derived protein hydrolysate at the soil level in vineyards on berry quality in a table grape variety, the Black Magic early table grapevine, during veraison. Our results demonstrate significant improvements in various parameters 14 days after application, including increased anthocyanin levels, enhanced sugar accumulation, and larger berry diameter while maintaining berry firmness. Transcriptomic analysis revealed mechanisms underlying these effects, highlighting the biostimulant's ability to expedite ripening processes while selectively modulating genes associated with cell wall metabolism, thus explaining the observed preservation of berry firmness. Furthermore, the treatment with a gluten-derived protein hydrolysate enhanced the grapevine's resilience to abiotic and biotic stresses, and several related genes were affected. This study sheds light on the potential of plant-derived biostimulants in grapevine cultivation, emphasizing the need for further research to elucidate their mechanisms and optimize agricultural practices.

Elucidating the Molecular Mechanisms and Comprehensive Effects of Sludge-Derived Plant Biostimulants on Crop Growth: Insights from Metabolomic Analysis

The utilization of urban waste for land management plays a crucial role in reshaping material flows between human activities and the environment. Sewage sludge alkaline thermal hydrolysis (ATH) produces sludge-derived plant biostimulants (SPB), which have garnered attention due to the presence of indole-3-acetic acid. However, there remains a gap in understanding SPB's molecular-level effects and its comprehensive impact on crops throughout their growth cycle. In this study, non-targeted and targeted metabolomic approaches are employed to analyze 51 plant hormones and 1,177 metabolites, revealing novel insights. The findings demonstrate that low concentrations of SPB exerted multiple beneficial effects on rice roots, leaves, and the root-soil system, facilitating rapid cell division and enhancing antioxidant defense mechanisms. These results provide a vital foundation for understanding ATH metabolic pathways and advocating for widespread SPB application, offering significant implications for sustainable land management.

Chemical case studies from natural products of recent interest in the crop protection industry

Covering: up to 2024This review showcases selected natural products, which are of high relevance to the craft of crop protection, including in its most recent aspects such as their non-cidal use as biostimulants in plant health. Focussing on the chemistry and associated structure-activity relationships that were disclosed, the review presents case studies from the recent chemical development of important natural products and compounds inspired by them for their use in the crop protection industry.

Bacillus endophytic strains control Fusarium wilt caused by Fusarium oxysporum f. sp. lycopersici in tomato cv. Perinha

Fusarium wilt is one of main phytopathology attacking tomato (Solanum lycopersicum L.) plantations in Brazil. Plant rhizosphere and endophytic beneficial microorganism are well known as plant growth promoters and biocontrol agents. The present study aims to evaluate the potential of different Bacillus strains as biocontrol agent to Fusarium oxysporum f. sp. lycopersici Race 3 strains; and also as plant growth promoting bacteria on Solanum lycopersicum cv Perinha. Different in vitro and greenhouse experiments were carried out to evaluate the direct and indirect bacterial-fungus antagonism, and they inoculation effects on plant traits. In vitro direct, metabolites, and volatile antagonism analysis demonstrated that B. toyonensis BR 10491(FORT 02) presented a broad antagonism to all tested race 3 FOL strains while B. megaterium BR 10466 (FORT 12), B. aryabhattai BR 10494 (FORT 25), B. stratosphericus BR 10438 (FORT 29) and B. cereus BR 10493 (FORT 113.1) strains showed significant antagonistic activity for at least two applied methods. Greenhouse pot experiments demonstrated a significant BCA effect of FORT 113.1 and FORT 02 against FOL Race 3 Fus 1302 strain during different tomato development stages (seedling, vegetative, and reproductive). Bacillus cereus (FORT 113.1) showed significantly higher shoot and height fresh weight, Chlorophyll a and Chlorophyll b content, stomata conductance, water use efficiency, and also a lower xylem infection percentage during vegetative and reproductive stages. Antioxidant enzymatic components analysis demonstrated a synergic effect of Fusarium and Bacillus inoculation, leading to a higher superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activity. In conclusion, the results suggest that strain FORT113.1 could be considered as a good candidate for production of new biofungicide with high potential to augment the existing biocontrol strategies.

Chitosan-strigolactone mimics with synergistic effect: A new concept for plant biostimulants

The paper reports new multifunctional plant biostimulant formulations obtained via in situ hydrogelation of chitosan with salicylaldehyde in the presence of a mimetic naphthalimide-based strigolactone, in specific conditions. Various analytical techniques (FTIR, 1H NMR, SEM, POM, TGA, WRXD) were employed to understand the particularities of the hydrogelation mechanism and its consequences on the formulations' properties. Further, in order to evaluate their potential for the targeted application, the swelling in media of pH characteristic for different soils, water holding capacity, soil biodegradability, in vitro release of the strigolactone mimic and impact on tomatoes plant growth in laboratory conditions were investigated and discussed. It was found that the strigolactone mimic has the ability to bond to the chitosan matrix via physical forces, favoring a prolonged release. Moreover, the combination of chitosan with the strigolactone mimic in an optimal mass ratio triggered a synergistic effect on the plant growth, up to 4 times higher compared to the neat control soil.

Adaptation of Rhizobium leguminosarum sv. trifolii strains to low temperature stress in both free-living stage and during symbiosis with clover

Legume-rhizobial symbiosis plays an important role in agriculture and ecological restoration. This process occurs within special new structures, called nodules, formed mainly on legume roots. Soil bacteria, commonly known as rhizobia, fix atmospheric dinitrogen, converting it into a form that can be assimilated by plants. Various environmental factors, including a low temperature, have an impact on the symbiotic efficiency. Nevertheless, the effect of temperature on the phenotypic and symbiotic traits of rhizobia has not been determined in detail to date. Therefore, in this study, the influence of temperature on different cell surface and symbiotic properties of rhizobia was estimated. In total, 31 Rhizobium leguminosarum sv. trifolii strains isolated from root nodules of red clover plants growing in the subpolar and temperate climate regions, which essentially differ in year and day temperature profiles, were chosen for this analysis. Our results showed that temperature has a significant effect on several surface properties of rhizobial cells, such as hydrophobicity, aggregation, and motility. Low temperature also stimulated EPS synthesis and biofilm formation in R. leguminosarum sv. trifolii. This extracellular polysaccharide is known to play an important protective role against different environmental stresses. The strains produced large amounts of EPS under tested temperature conditions that facilitated adherence of rhizobial cells to different surfaces. The high adaptability of these strains to cold stress was also confirmed during symbiosis. Irrespective of their climatic origin, the strains proved to be highly effective in attachment to legume roots and were efficient microsymbionts of clover plants. However, some diversity in the response to low temperature stress was found among the strains. Among them, M16 and R137 proved to be highly competitive and efficient in nodule occupancy and biomass production; thus, they can be potential yield-enhancing inoculants of legumes.

Antioxidant activity and comparative RNA-seq analysis support mitigating effects of an algae-based biostimulant on drought stress in tomato plants

Drought is a significant global environmental stress. Biostimulants offer a sustainable solution to enhance crop tolerance and mitigate productivity losses. This study assessed the impact of foliar application of ERANTHIS®, a biostimulant derived from the algae Ascophyllum nodosum and Laminaria digitata and yeast extracts, on tomato plants under mild water stress. Evaluations were conducted at 5 and 24 hours after the third treatment. Under optimal water conditions, the biostimulant showed a priming effect, with an early increase of stress markers and a timing-specific modulation of ROS non enzymatic and enzymatic ROS scavenging activities. Under drought stress, the biostimulant later decreased stress markers, by aligning the majority of analyzed ROS scavengers closer to levels in well-irrigated plants. Transcriptome analysis using RNA-seq data revealed differentially expressed genes (DEGs) and multivariate data highlighted groups of co-regulated genes (k-means clustering). Genes involved in water channel activity, transcription regulator activity, and oxidoreductase activity were significantly modulated. Cluster analysis identified distinct gene clusters influenced by the biostimulant under optimal conditions, including early responses (cell wall modification, hormone signaling) and late responses (RNA modification, nutrient uptake process). Under water stress, early responses involved actin filament organization and MAPK signaling, while late responses were related to plasma membrane components and cell wall organization. This study, integrating biochemical and transcriptomic data, provides a comprehensive understanding of how a biostimulant primes plants under optimal conditions and mitigates water stress effects, offering valuable insights for sustainable agriculture.

Effects of Biostimulants on the Eco-Physiological Traits and Fruit Quality of Black Chokeberry (Aronia melanocarpa L.)

Biostimulants contribute to the physiological growth of plants by enhancing the quality characteristics of fruit without harming the environment. In addition, biostimulants applied to plants strengthen nutritional efficiency, abiotic stress tolerance, and fruit biochemical traits. We investigated the effectiveness of specific organic biostimulants. Five treatments were tested: (1) control (H2O, no biostimulants); (2) Magnablue + Keyplex 350 (Mgl + Kpl350); (3) Cropobiolife + Keyplex 120 (Cpl + Kpl120); (4) Keyplex 120 (Kpl120); and (5) Magnablue + Cropobiolife + Keyplex 120 (Mgl + Cpl + Kpl120) on the mineral uptake and physiology in black chokeberry (Aronia) plants, as well as the quality of their berries. The different treatments were applied to three-year-old chokeberry plants, and the experimental process in the field lasted from May to September 2022 until the harvest of ripe fruits. Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) revealed that the fifth treatment significantly increased concentrations of P, Ca, and K. Additionally, the fifth treatment enhanced photochemical efficiency (Fv/Fm), water-splitting efficiency (Fv/Fo) in PSII, and the performance index (PI) of both PSI and PSII in chokeberry leaves. Improvements in photosynthesis, such as CO2 assimilation (A), transpiration (E), and water-use efficiency (A/E), were also noted under biostimulant applications. Upon harvesting the ripe fruits, part of them was placed at room temperature at 25 °C, while the rest were stored at 4 °C, RH 90% for 7 days. The cultivation with biostimulants had beneficial effects on the maintenance of flesh consistency, ascorbic acid concentration, and weight of berries at 4 and 25 °C, especially in the 5th treatment. Moreover, the total antioxidant capacity, anthocyanin concentration, and total phenols of the berries were notably higher in the third and fifth treatments compared to the control. These data suggest that selecting appropriate biostimulants can enhance plant yield and fruit quality by potentially activating secondary metabolite pathways.

Enhancing carotenoid accumulation in Dunaliella bardawil by combined treatments with fulvic acid and optimized culture conditions

Natural carotenoids from microalgae have received more attention as an alternative source. In this study, fulvic acid (FA), a plant growth regulator, was used to enhance carotenoid accumulation in microalgae Dunaliella bardawil rich in lutein. However, the addition of FA promoted pigment synthesis but also exhibited an inhibitory effect on biomass. Therefore, the optimization of culture conditions was performed to further enhance carotenoid accumulation, including high light stress (10,000 lx) and the two-stage cultivation comprising 1-aminocyclopropane-1-carboxylic acid (ACC) and FA. Under both culture conditions, the growth inhibition caused by FA was alleviated, leading to a further increase in the contents of chlorophylls and carotenoids. HPLC analysis revealed that the production of lutein, α-carotene and β-carotene increased by 0.44-, 0.37- and 0.54-fold under the treatment of 400 mg/L FA with high light intensity and 0.91-, 1.15-0.29-fold under the two-stage cultivation comprising 11 mM ACC and 500 mg/L FA. Furthermore, algal cells under FA treatment and the two-stage cultivation stained with Bodipy505/515 emitted stronger fluorescence under a laser confocal microscope, suggesting that lipid accumulation was increased. Additionally, the transcription levels of carotenogenic genes were also found to be up-regulated by qRT-PCR. These results indicated an enhancement in both the storage capacity and synthesis of carotenoids in D. bardawil. This study revealed the potential application of plant growth regulators in promoting carotenoid accumulation in D. bardawil which could be further improved by optimizing the culture conditions, providing a reference for efficient carotenoid production in microalgae.

Impact of biopolymer-based Trichoderma harzianum seed coating on disease incidence and yield in oilseed crops

The use of microbe-based biological control for crop pests is recognized as an environmentally safe substitute for conventional chemical pesticides. However, the practical application of microbial inoculants in large-scale agriculture is underexplored, impeding their widespread commercial adoption. This study addresses the scarcity of research on effective delivery methods for microbial inoculants, particularly through seed coating, which has the potential to be a cost- and time-efficient strategy in crop management. In this research, the Trichoderma harzianum strain Th4d, a biological control agent (BCA), was incorporated into specially formulated biopolymeric compositions based on chitosan and cellulose. The efficacy of this seed coating approach was tested against various soil- and seed-borne pathogens in oilseed crops, including soybean, groundnut, and safflower. Results indicate that safflower treated with the biopolymer chitosan-based T. harzianum Th4d 1 % liquid formulation blend exhibited a higher seed yield of 793 kg/ha, seed germination of 84.7 %, and a significant reduction in wilt and root rot by 64.7 %. In groundnut crops, the seed coating led to a seed germination rate of 88.6 %, a 72 % reduction in root rot incidence, and a seed yield of 3040 kg/ha. Similarly, soybean crops treated with the biopolymer chitosan and T. harzianum Th4d displayed 83.4 % seed germination, a 70.9 % reduction in root rot, and a seed yield of 1239 kg/ha. Further on-farm evaluations demonstrated promising results, with the biopolymer chitosan-based T. harzianum Th4d 1 % liquid formulation blend seed treatment showing a high incremental cost-benefit ratio in safflower (1:4.5), soybean (1:2.5), and groundnut crops (1:3.3). This study underscores the potential of microbe-based seed coating as a sustainable and economically viable strategy for pest management in oilseed crops."

Optimizing oilseed rape growth: Exploring the effect of foliar biostimulants on the interplay among metabolism, phenology, and yield

The current agricultural system is in search of new strategies to achieve a more sustainable production while keeping or even increasing crop yield and quality. In this scenario, the application of biostimulants constitutes a potent solution. In the current study, the impact of a blue-green microalgal extract (MB) and a pig tissue hydrolysate (PTH) on rapeseed plants' development was characterized. Obtained results revealed a positive effect on yield parameters of plants treated with MB and, especially, PTH; this was associated to an improvement on the photosynthetic performance. Moreover, this study remarked the effects of biostimulants on plant phenology through their pivotal role in modulating developmental processes. More specifically, proteomic, metabolomic, and hormone content analyses revealed distinct alterations associated with the acceleration of phenology induced by biostimulant application. Additionally, some antioxidant enzymes and stress-related compounds were up-regulated upon MB and PTH treatments, indicating enhanced plant defense mechanisms in response to accelerated phenological transitions. Such findings highlight the intricate interplay between biostimulants and plant physiology, wherein biostimulants orchestrate rapid developmental changes, ultimately influencing growth dynamics. Altogether, the current study reveals that the application of both MB and PTH biostimulants promoted rapeseed plant phenology and productivity associated with an improvement in the photosynthetic machinery while boosting other physiological and molecular mechanisms.

Mitigating the Accumulation of Mercury (Hg) and Lead (Pb) through Humic Acid Application under Aquaponic Conditions Using Watercress (Nasturtium officinale R. Br.) as a Model Plant

In aquaponic farming, there is a potential risk that heavy metals will contaminate the water, which can lead to heavy metal accumulation in the plants. Our research investigated the accumulation of mercury (Hg) and lead (Pb) under aquaponic conditions and the effect of their increased presence on the uptake of other macro- and micronutrients using watercress (Nasturtium officinale) as a model plant. The potential modifying effect of humic acid on heavy metal accumulation was also investigated. Adding Hg and Pb increased the mercury and lead levels of the watercress plants to over 300 µg kg-1, while the addition of humic acid significantly reduced the concentration of both mercury and lead in the plants compared to plants treated with heavy metals alone, from 310.647 µg kg-1 to 196.320 µg kg-1 for Hg and from 313.962 µg kg-1 to 203.508 µg kg-1 for Pb. For Fe and Mn, higher values were obtained for the Hg + humic acid treatments (188.13 mg kg-1 and 6423.92 µg kg-1, respectively) and for the Pb + humic acid treatments (198.26 mg kg-1 and 6454.31 µg kg-1, respectively). Conversely, the Na, K, Cu levels were lower compared to those in plants treated with heavy metals alone. Our results demonstrated that watercress can accumulate mercury, leading to high levels, even above food safety standards, highlighting the importance of water quality control in aquaponic systems. Furthermore, these results suggest that watercress could be used as a natural filter in recirculation systems. The addition of humic acid significantly reduced the accumulation of heavy metals and altered the element content in the plant.

Protein enrichment of the red macroalga Palmaria palmata using pulsed electric field and enzymatic processing

The human population is steadily increasing and new alternative protein sources are necessary to secure food safety. There is a growing interest in macroalgae, or seaweed, as an alternative food source as they are rich in nutrients, minerals and carbohydrates. Among the diverse species of macroalga, Palmaria palmata, a red seaweed of growing interest due to its high protein content, represents a potential candidate for contributing to food security and animal feed. Novel methods are being investigated for extracting valuable components from seaweed, including protein. In this study, pulsed electric field (PEF) and enzymatic assisted extraction (EAE) were tested to investigate whether the methods, alone or in combination, were sufficient for protein extraction from P. palmata. The results show high extraction yields of dry matter consisting mostly of carbohydrates and ash when using EAE. The results point to a concentration of protein, including essential amino acids, in the pellet after extraction with a combination of PEF and EAE, or EAE alone. There is potential for the protein-rich pellet in animal feed. For the supernatant, there are potential uses within biostimulants.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10811-024-03338-3.

Plant-derived biostimulant as priming agents enhanced antioxidant and nutritive properties in brassicaceous microgreens

BACKGROUND

Microgreens constitute dietary sources of bioactive compounds imparting numerous health benefits and enhancing sensory experience. They can be successfully cultivated in soilless systems where biostimulants can be easily integrated as seed-priming and post-germination agents improving the sustainability of a crop's final production. Compared to an untreated control, three priming agents (a commercial legume-derived protein hydrolysate (A250), a novel protein hydrolysate derived from peanut biomass (H250) and hydropriming (H2O)) were applied to Komatsuna and Mibuna seeds grown as microgreens and compared for their effects on yield parameters, mineral composition, ABTS and FRAP antioxidant capacity, carotenoid concentration and phenolic compounds.

RESULTS

Significant effects of the main experimental factors and their interactions were identified on antioxidant capacity. Compared to the control and hydropriming, the highest ABTS and FRAP values were observed in Mibuna with the A250 and H250 treatments, respectively. Additionally, the H250 treatment increased the total concentrations of phenolic acid derivatives and flavonoid derivatives in Mibuna and Komatsuna, in tune with the levels of total flavonoids. Concerning mineral composition, the highest concentrations in both species were those of phosphorus and nitrate.

CONCLUSION

These results highlight the potential of select plant-based biostimulants as priming agents to enhance the antioxidant capacity, nutrient content and bioactive compound content, thus further increasing their functional and nutritive quality. In the light of this, the possibility of reducing the application of fertilizers by promoting a green transition for the intensive production of microgreens could subsequently be evaluated. © 2024 Society of Chemical Industry.

Recirculating frass from food waste bioconversion using black soldier fly larvae: Impacts on process efficiency and product quality

Biowaste generation is increasing worldwide and inadequate disposal has strong negative impacts on food systems and ecosystems. Biodigestion of biowaste using black soldier fly (Hermetia illucens) larvae (BSFL) generates valuable by-products such as animal feed (larval biomass) and organic fertiliser (frass). However, the latter is typically unstable immediately after waste conversion and is thus unsafe for use as a fertilizer in terms of maturity. This study evaluated recirculation of frass within bioconversion of post-consumer food waste (FW) as a dietary component for BSFL to improve the quality of the subsequent frass obtained. Frass was introduced at increasing inclusion levels replacing food waste (2.5-100% on wet-weight basis) as part of the larvae's feeding substrate. Bioconversion efficiency and material reduction were significantly reduced by frass inclusion, while larval yield per experimental unit remained unchanged. When considering only the waste component in the larval diet, larval yield (dry-weight basis) ranged between 207 (0% frass inclusion) and 403 (40% frass inclusion) kg tonne FW-1, thus increasing by up to 94% at higher frass inclusion. With increasing dietary inclusion rate of frass from 0% to 100%, crude protein content of larval biomass increased by 41%, while fat content was reduced by 32%. The recirculated frass (obtained after including frass in the larval diet) had elevated concentrations of P, K, S, Na and B and around 6% lower organic matter content, demonstrating a higher degree of decomposition. Frass inclusion in the larval diet generated recirculated frass that were more stable and mature, as indicated by self-heating capacity, CO2 and NH3 volatilisation, seed germination bioassays and other parameters. It was concluded that frass recirculation improves waste bioconversion efficiency in relation to food waste unit, as well as larval biomass and frass quality, ensuring safer use as a fertilizer.

Redox Regulation by Priming Agents Toward a Sustainable Agriculture

Plants are sessile organisms that are often subjected to a multitude of environmental stresses, with the occurrence of these events being further intensified by global climate change. Crop species therefore require specific adaptations to tolerate climatic variability for sustainable food production. Plant stress results in excess accumulation of reactive oxygen species leading to oxidative stress and loss of cellular redox balance in the plant cells. Moreover, enhancement of cellular oxidation as well as oxidative signals has been recently recognized as crucial players in plant growth regulation under stress conditions. Multiple roles of redox regulation in crop production have been well documented, and major emphasis has focused on key redox-regulated proteins and non-protein molecules, such as NAD(P)H, glutathione, peroxiredoxins, glutaredoxins, ascorbate, thioredoxins and reduced ferredoxin. These have been widely implicated in the regulation of (epi)genetic factors modulating growth and health of crop plants, with an agricultural context. In this regard, priming with the employment of chemical and biological agents has emerged as a fascinating approach to improve plant tolerance against various abiotic and biotic stressors. Priming in plants is a physiological process, where prior exposure to specific stressors induces a state of heightened alertness, enabling a more rapid and effective defense response upon subsequent encounters with similar challenges. Priming is reported to play a crucial role in the modulation of cellular redox homeostasis, maximizing crop productivity under stress conditions and thus achieving yield security. By taking this into consideration, the present review is an up-to-date critical evaluation of promising plant priming technologies and their role in the regulation of redox components toward enhanced plant adaptations to extreme unfavorable environmental conditions. The challenges and opportunities of plant priming are discussed, with an aim of encouraging future research in this field toward effective application of priming in stress management in crops including horticultural species.

Fulvic acid application increases rice seedlings performance under low phosphorus stress

BACKGROUND

Fulvic acid enhances plant growth and interacts synergistically with phosphate fertilizer to alleviate the agricultural production problem of low phosphorus fertilizer utilization efficiency. However, the underlying mechanism of its action remains poorly understood. In this study, we investigated the impact of fulvic acid application with varying concentrations (0, 40, 60, 80 and 120 mg/L) on rice performance in plants grown in a hydroponic system subjected to low phosphorus stress. The rice growth phenotypes, biomass, root morphology, phosphorus uptake, and the impact of fulvic acid on the rhizosphere environment of rice, were assessed.

RESULTS

The findings showed that adding appropriate concentrations of exogenous fulvic acid could promote the growth performance of rice under low phosphorus stress. Particularly at T1 (40 mg/L) and T2 (60 mg/L) over the control effectively increased rice biomass by 25.42% and 24.56%, respectively. Fulvic acid treatments stimulated root morphogenesis, up-regulated phosphate transporter genes, and facilitated phosphorus absorption and accumulation. Especially T1 (20.52%), T2 (18.10%) and T3 (20.48%) treatments significantly increased phosphorus uptake in rice, thereby alleviating low phosphorus stress. Additionally, fulvic acid elevated organic acids concentration in roots and up-regulated plasma membrane H+-ATPase genes, promoting organic acids secretion. This metabolic alteration can also alleviate low phosphorus stress in rice.

CONCLUSIONS

The effect of exogenous fulvic acid on physiological indicators is concentration-dependent under low phosphorus stress, enhances rice performance and reduces reliance on phosphorus fertilizer. This provides new insights to shed light on the mechanism of alleviating low phosphorus stress in rice through fulvic acid application, an eco-friendly tool.

Hydroponics with Microalgae and Cyanobacteria: Emerging Trends and Opportunities in Modern Agriculture

The global population is expected to reach 9.5 billion, which means that crop productivity needs to double to meet the growing population's food demand. Soil degradation and environmental factors, such as climate events, significantly threaten crop production and global food security. Furthermore, rapid urbanization has led to 55% of the world's population migrating to cities, and this proportion is expected to increase to 75% by 2050, which presents significant challenges in producing staple foods through conventional hinterland farming. Numerous studies have proposed various sustainable farming techniques to combat the shortage of farmable land and increase food security in urban areas. Soilless farming techniques such as hydroponics have gained worldwide popularity due to their resource efficiency and production of superior-quality fresh products. However, using chemical nutrients in a conventional hydroponic system can have significant environmental impacts, including eutrophication and resource depletion. Incorporating microalgae into hydroponic systems as biostimulants offers a sustainable and ecofriendly approach toward circular bioeconomy strategies. The present review summarizes the plant growth-promoting activity of microalgae as biostimulants and their mechanisms of action. We discuss their effects on plant growth parameters under different applications, emphasizing the significance of integrating microalgae into a closed-loop circular economy model to sustainably meet global food demands.

Enriching NPK Mineral Fertilizer with Plant-Stimulating Peptides Increases Soilless Tomato Production, Grower Profit, and Environmental Sustainability

The need to increase agricultural production to feed a steadily growing population may clash with the more environmentally friendly but less efficient production methods required. Therefore, it is important to try to reduce the use of chemical inputs without compromising production. In this scenario, natural biostimulants have become one of the most sought-after and researched technologies. In the present study, the results of a greenhouse experiment on hydroponic tomatoes (Solanum lycopersicum L.) are presented, which involved comparing the use of ordinary NPK fertilizer (Cerbero®) with the use of NPK fertilizers enriched with 0.5% protein hydrolysate of plant origin (Cerbero Green®) at both standard (100%) and reduced (70%) fertilization rates. The results highlight how the use of Cerbero Green® fertilizers improves the production performance of tomatoes. More specifically, they show that the use of Cerbero Green® leads to higher marketable yields, especially under reducing fertilizer use, ensuring a positive net change in profit for the grower. In addition, carbon footprint analysis has revealed that the use of Cerbero Green® reduces the environmental impact of hydroponic tomato growing practices by up to 8%. The observed higher yield of hydroponically grown tomatoes even with reduced fertilization rates underlines once again the key role of natural biostimulants in increasing both the economic and environmental sustainability of horticultural production.

Selenium Nanoparticle and Melatonin Treatments Improve Melon Seedling Growth by Regulating Carbohydrate and Polyamine

Bio-stimulants, such as selenium nanoparticles and melatonin, regulate melon growth. However, the effects of individual and combined applications of selenium nanoparticles and melatonin on the growth of melon seedlings have not been reported. Here, two melon cultivars were sprayed with selenium nanoparticles, melatonin, and a combined treatment, and physiological and biochemical properties were analyzed. The independent applications of selenium nanoparticles, melatonin, and their combination had no significant effects on the plant heights and stem diameters of Jiashi and Huangmengcui melons. Compared with the controls, both selenium nanoparticle and melatonin treatments increased soluble sugars (6-63%) and sucrose (11-88%) levels, as well as the activity of sucrose phosphate synthase (171-237%) in melon leaves. The phenylalanine ammonia lyase (29-95%), trans cinnamate 4-hydroxylase (32-100%), and 4-coumaric acid CoA ligase (26-113%), as well as mRNA levels, also increased in the phenylpropanoid metabolism pathway. Combining the selenium nanoparticles and melatonin was more effective than either of the single treatments. In addition, the levels of superoxide dismutase (43-130%), catalase (14-43%), ascorbate peroxidase (44-79%), peroxidase (25-149%), and mRNA in melon leaves treated with combined selenium nanoparticles and melatonin were higher than in controls. The results contribute to our understanding of selenium nanoparticles and melatonin as bio-stimulants that improve the melon seedlings' growth by regulating carbohydrate, polyamine, and antioxidant capacities.

Next generation plant biostimulants & genome sequencing strategies for sustainable agriculture development

The best environment for plant growth and development contains certain essential metabolites. A broad category of metabolites known as "plant biostimulants" (PBs) includes biomolecules such as proteins, carbohydrates, lipids, and other secondary metabolites related to groups of terpenes, specific nitrogen-containing compounds, and benzene ring-conjugated compounds. The formation of biomolecules depends on both biotic and abiotic factors, such as the release of PB by plants, animals, and microorganisms, or it can result from the control of temperature, humidity, and pressure in the atmosphere, in the case of humic substances (HSs). Understanding the genomic outputs of the concerned organism (may be plants or others than them) becomes crucial for identifying the underlying behaviors that lead to the synthesis of these complex compounds. For the purposes of achieving the objectives of sustainable agriculture, detailed research on PBs is essential because they aid in increasing yield and other growth patterns of agro-economic crops. The regulation of homeostasis in the plant-soil-microbe system for the survival of humans and other animals is mediated by the action of plant biostimulants, as considered essential for the growth of plants. The genomic size and gene operons for functional and regulation control have so far been revealed through technological implementations, but important gene annotations are still lacking, causing a delay in revealing the information. Next-generation sequencing techniques, such as nanopore, nanoball, and Illumina, are essential in troubleshooting the information gaps. These technical advancements have greatly expanded the candidate gene openings. The secondary metabolites being important precursors need to be studied in a much wider scale for accurate calculations of biochemical reactions, taking place inside and outside the synthesized living cell. The present review highlights the sequencing techniques to provide a foundation of opportunity generation for agricultural sustainability.

Lettuce (Lactuca sativa L.) Cultures and the Bioactivity of Their Root Microflora Are Affected by Amended Soil

This study aimed to highlight the positive effects of various recycled organic substrates on lettuce plants (Lactuca sativa L.) and to promote sustainable waste management practices, contributing to the concept of a circular economy. Over a two-month period, the growth potential and rhizosphere microflora of lettuce plants grown in soil amended with different recycled substrates were investigated. All data were compared, and the effects of the culture substrates were evaluated. All groups containing soil improvers offered a significant increase in the number of leaves per plant and, in two cases, an increase in dry biomass as well as an increase in the concentration of all leaf pigments. Both MDA and H2O2 concentrations were the lowest in two groups containing soil improvers (VG 5% and PLUS 10%). At the end of the culture period, isolation and culture of bacteria from the plant rhizosphere were performed. Different bacterial strains were isolated and tested for the production of antimicrobial agents against six microbial indicators (B. subtilis, E. coli, S. aureus, S. cerevisiae, C. albicans, and P. aeruginosa). The greater percentage of the isolated strains showed an ability to inhibit the growth of the B. subtilis index. Most of the strains with antimicrobial activity were isolated from the soil samples of the plain soil group and the soil amended with the commercial fertilizer. Three of the isolated strains originating from the Ginagro 5% group are multiproducers as they inhibit the growth of three microbial indicators or more.

Foliar application of various biostimulants produces contrasting response on yield, essential oil and chemical properties of organically grown sage (Salvia officinalis L.)

Sage (Salvia officinalis L.) is a medicinal and aromatic plant (MAP) belonging to the Lamiaceae family. Its morphological, productive and chemical characteristics are affected by abiotic and biotic factors. The use of biostimulants seems to be one of the most interesting innovative practices due to fact they can represent a promising approach for achieving sustainable and organic agriculture. Despite a large application in horticulture, the use of biostimulants on MAPs has been poorly investigated. On this basis, a field experiment in a 2-year study was done to assess the effect of foliar treatments with different types of biostimulants (containing seaweeds, fulvic acids and protein hydrolysates) and two frequencies of application on morphological, productive, and chemical characteristics of S. officinalis grown organically in Mediterranean environment. Morphological, productive, and chemical parameters were affected by the factors. The biostimulant application generated higher plant height, chlorophyll content, relative water content, biomass yield and essential oil yield compared to control plants. In addition, more frequent application of biostimulants produced higher biomass and essential oil yield. The application of fulvic acid and protein hydrolysates every week produced the highest total fresh yields (between 3.9 and 8.7 t ha-1) and total dry yields (between 1.3 and 2.5 t ha-1). The essential oil yield almost doubled (33.9 kg ha-1) with a higher frequency of protein hydrolysates application. In this study, 44 essential oil compounds were identified, and the frequency factor significantly influenced the percentage of 38 compounds. The highest percentage of some of the most representative monoterpenes, such as 1,8-cineole, α-thujone and camphor, were observed in biostimulated plants, with average increases between 6% and 35% compared to control plants. The highest values for total phenolics, rosmarinic acid, antioxidant activity were obtained in control plants and with a lower frequency of biostimulant applications. This study emphasizes how biostimulant applications may be used to improve sage production performance and essential oil parameters when produced in agricultural organic system. At the same time, biostimulants application caused a decrease in total phenolic, antioxidant activity and rosmarinic acid values.

Mitigation of drought stress in chili plants (Capsicum annuum L.) using mango fruit waste biochar, fulvic acid and cobalt

Drought stress can have negative impacts on crop productivity. It triggers the accumulation of reactive oxygen species, which causes oxidative stress. Limited water and nutrient uptake under drought stress also decreases plant growth. Using cobalt and fulvic acid with biochar in such scenarios can effectively promote plant growth. Cobalt (Co) is a component of various enzymes and co-enzymes. It can increase the concentration of flavonoids, total phenols, antioxidant enzymes (peroxidase, catalase, and polyphenol oxidase) and proline. Fulvic acid (FA), a constituent of soil organic matter, increases the accessibility of nutrients to plants. Biochar (BC) can enhance soil moisture retention, nutrient uptake, and plant productivity during drought stress. That's why the current study explored the influence of Co, FA and BC on chili plants under drought stress. This study involved 8 treatments, i.e., control, 4 g/L fulvic acid (4FA), 20 mg/L cobalt sulfate (20CoSO4), 4FA + 20CoSO4, 0.50%MFWBC (0.50 MFWBC), 4FA + 0.50MFWBC, 20CoSO4 + 0.50MFWBC, 4FA + 20CoSO4 + 0.50MFWBC. Results showed that 4 g/L FA + 20CoSO4 with 0.50MFWBC caused an increase in chili plant height (23.29%), plant dry weight (28.85%), fruit length (20.17%), fruit girth (21.41%) and fruit yield (25.13%) compared to control. The effectiveness of 4 g/L FA + 20CoSO4 with 0.50MFWBC was also confirmed by a significant increase in total chlorophyll contents, as well as nitrogen (N), phosphorus (P), and potassium (K) in leaves over control. In conclusion4g/L, FA + 20CoSO4 with 0.50MFWBC can potentially improve the growth of chili cultivated in drought stress. It is suggested that 4 g/L FA + 20CoSO4 with 0.50MFWBC be used to alleviate drought stress in chili plants.

Biostimulants: A sufficiently effective tool for sustainable agriculture in the era of climate change?

Climate change is currently considered as one of the main concerns of the agriculture sector, as it limits crop production and quality. Furthermore, the current context of global crisis with international political instability and war conflicts over the world is pushing the agriculture sector even more to urgently boost productivity and yield and doing so in a sustainable way in the current frame of climate change. Biostimulants can be an effective tool in alleviating the negative effects of environmental stresses to which plants are exposed, such as drought, salinity, heavy metals and extreme temperatures etc. Biostimulants act through multiple mechanisms, modifying gene expression, metabolism and phytohormone production, promoting the accumulation of compatible solutes and antioxidants and mitigating oxidative stress. However, it is important to keep in mind that the use and effect of biostimulants has limitations and must be accompanied by other techniques to ensure crop yield and quality in the current frame of climate change, such as proper crop management and the use of other sustainable resources. Here, we will not only highlight the potential use of biostimulants to face future agricultural challenges, but also take a critical look at their limitations, underlining the importance of a broad vision of sustainable agriculture in the context of climate change.

Improving Tree Seedling Quality Using Humates Combined with Bacteria to Address Decarbonization Challenges through Forest Restoration

Improving the quality of tree planting material for carbon sequestration through reforestation can help solve environmental problems, including the need to reduce the concentration of carbon dioxide in the atmosphere. The purpose of this study was to investigate the possibility of using humic substances in combination with rhizosphere microorganisms Pseudomonas protegens DA1.2 and Pseudomonas sp. 4CH as a means to stimulate the growth of seedlings of pine, poplar, large-leaved linden, red oak, horse chestnut, and rowan. Humic substances stimulated the growth of shoots and roots of pine, large-leaved linden, and horse chestnut seedlings. The effects of bacteria depended on both plant and bacteria species: Pseudomonas protegens DA1.2 showed a higher stimulatory effect than Pseudomonas sp. 4CH on pine and linden, and Pseudomonas sp. 4CH was more effective in the case of chestnut. An additive effect of humates and Pseudomonas protegens DA1.2 on the growth rate of pine and linden saplings was discovered. Poplar, red oak, and rowan seedlings were unresponsive to the treatments. The growth-stimulating effects of the treatments are discussed in connection with the changes in carbon, chlorophyll, and nitrogen contents in plants. The results show the need for further research in bacterial species capable of stimulating the growth of plant species that were unresponsive in the present experiments.

Histological and Physiological Study of the Effects of Biostimulants and Plant Growth Stimulants in Viburnum opulus 'Roseum'

Biostimulants and other plant growth promoters can provide an effective solution to the challenge of urbanisation and climate change. Viburnum opulus 'Roseum' is a globally popular deciduous shrub species that can be made more resistant to urban influences by using natural growth-promoting substances. In our study, we investigated the effects of growth promoters Kelpak®, Bistep and Yeald Plus on the species, both histologically and physiologically (proline stress hormone measurement). Our measurements were complemented using the analysis of rhizosphere alkaline phosphatase, β-glucosidase and β-glucosaminidase enzymes, to obtain a more complete picture of the combined effect of biostimulants and species. We found that the Bistep biostimulant had an outstanding effect on the leaf tissue culture results of the variety. The transpiration and evapotranspiration findings also confirmed the efficacy of biostimulants. In the case of POD activity and rhizosphere enzyme measurements, Bistep and Yeald Plus obtained statistically higher values than the control group. Kelpak produced better results than the control group in several measurements (alkaline phosphatase levels; evapotranspiration results), but in other cases it resulted in lower values than the control treatment. The use of Bistep and Yeald Plus can greatly assist growers in the cultivation of V. opulus 'Roseum' in an urban environment.

NMR and LC-MS-based metabolomics to investigate the efficacy of a commercial bio stimulant for the treatment of wheat (Triticum aestivum)

INTRODUCTION

Bio stimulants are substances and/or microorganisms that are used to improve plant growth and crop yields by modulating physiological processes and metabolism of plants. While research has primarily focused on the broad effects of bio stimulants in crops, understanding their cellular and molecular influences in plants, using metabolomic analysis, could elucidate their effectiveness and offer possibilities for fine-tuning their application. One such bio stimulant containing galacturonic acid as elicitor is used in agriculture to improve wheat vigor and strengthen resistance to lodging.

OBJECTIVE

However, whether a metabolic response is evolved by plants treated with this bio stimulant and the manner in which the latter might regulate plant metabolism have not been studied.

METHOD

Therefore, the present study used 1H-NMR and LC-MS to assess changes in primary and secondary metabolites in the roots, stems, and leaves of wheat (Triticum aestivum) treated with the bio stimulant. Orthogonal partial least squares discriminant analysis effectively distinguished between treated and control samples, confirming a metabolic response to treatment in the roots, stems, and leaves of wheat.

RESULTS

Fold-change analysis indicated that treatment with the bio stimulation solution appeared to increase the levels of hydroxycinnamic acid amides, lignin, and flavonoid metabolism in different plant parts, potentially promoting root growth, implantation, and developmental cell wall maturation and lignification.

CONCLUSION

These results demonstrate how non-targeted metabolomic approaches can be utilized to investigate and monitor the effects of new agroecological solutions based on systemic responses.

Unraveling the effect of phenolic extract derived from olive mill solid wastes on agro-physiological and biochemical traits of pomegranate and its associated rhizospheric soil properties

Agricultural waste management poses a significant challenge in circular economy strategies. Olive mill wastes (OMW) contain valuable biomolecules, especially phenolic compounds, with significant agricultural potential. Our study evaluate the effects of phenolic extract (PE) derived from olive mill solid wastes (OMSW) on pomegranate agro-physiological and biochemical responses, as well as soil-related attributes. Pomegranate plants were treated with PE at doses of 100 ppm and 200 ppm via foliar spray (L100 and L200) and soil application (S100 and S200). Results showed increased biomass with PE treatments, especially with soil application (S100 and S200). Proline and soluble sugar accumulation in leaves suggested plant adaptation to PE with low-level stress. Additionally, PE application reduced malondialdehyde (MDA) and hydrogen peroxide (H2O2) contents. Higher doses of PE (S200) significantly improved net photosynthesis (Pn), transpiration rate (E), water use efficiency (WUEi), and photosynthetic efficiency (fv/fm and PIabs). Furthermore, PE treatments enhanced levels of chlorophylls, carotenoids, polyphenols, flavonoids, and antioxidant activity. Soil application of PE also increased soil enzyme activities and microbial population. Our findings suggest the beneficial impact of PE application on pomegranate agro-physiological responses, laying the groundwork for further research across various plant species and soil types to introduce nutrient-enriched PE as an eco-friendly biostimulant.

Cytokinin-deficient Chlamydomonas reinhardtii CRISPR-Cas9 mutants show reduced ability to prime resistance of tobacco against bacterial infection

Although microalgae have only recently been recognized as part of the plant and soil microbiome, their application as biofertilizers has a tradition in sustainable crop production. Under consideration of their ability to produce the plant growth-stimulating hormone cytokinin (CK), known to also induce pathogen resistance, we have assessed the biocontrol ability of CK-producing microalgae. All pro- and eukaryotic CK-producing microalgae tested were able to enhance the tolerance of tobacco against Pseudomonas syringae pv. tabaci (PsT) infection. Since Chlamydomonas reinhardtii (Cre) proved to be the most efficient, we functionally characterized its biocontrol ability. We employed the CRISPR-Cas9 system to generate the first knockouts of CK biosynthetic genes in microalgae. Specifically, we targeted Cre Lonely Guy (LOG) and isopentenyltransferase (IPT) genes, the key genes of CK biosynthesis. While Cre wild-type exhibits a strong protection, the CK-deficient mutants have a reduced ability to induce plant defence. The degree of protection correlates with the CK levels, with the IPT mutants showing less protection than the LOG mutants. Gene expression analyses showed that Cre strongly stimulates tobacco resistance through defence gene priming. This study functionally verifies that Cre primes defence responses with CK, which contributes to the robustness of the effect. This work contributes to elucidate microalgae-mediated plant defence priming and identifies the role of CKs. In addition, these results underscore the potential of CK-producing microalgae as biologicals in agriculture by combining biofertilizer and biocontrol ability for sustainable and environment-friendly crop management.

Unravelling the biostimulant activity of a protein hydrolysate in lettuce plants under optimal and low N availability: a multi-omics approach

The application of protein hydrolysates (PH) biostimulants is considered a promising approach to promote crop growth and resilience against abiotic stresses. Nevertheless, PHs bioactivity depends on both the raw material used for their preparation and the molecular fraction applied. The present research aimed at investigating the molecular mechanisms triggered by applying a PH and its fractions on plants subjected to nitrogen limitations. To this objective, an integrated transcriptomic-metabolomic approach was used to assess lettuce plants grown under different nitrogen levels and treated with either the commercial PH Vegamin® or its molecular fractions PH1(>10 kDa), PH2 (1-10 kDa) and PH3 (<1 kDa). Regardless of nitrogen provision, biostimulant application enhanced lettuce biomass, likely through a hormone-like activity. This was confirmed by the modulation of genes involved in auxin and cytokinin synthesis, mirrored by an increase in the metabolic levels of these hormones. Consistently, PH and PH3 upregulated genes involved in cell wall growth and plasticity. Furthermore, the accumulation of specific metabolites suggested the activation of a multifaceted antioxidant machinery. Notwithstanding, the modulation of stress-response transcription factors and genes involved in detoxification processes was observed. The coordinated action of these molecular entities might underpin the increased resilience of lettuce plants against nitrogen-limiting conditions. In conclusion, integrating omics techniques allowed the elucidation of mechanistic aspects underlying PH bioactivity in crops. Most importantly, the comparison of PH with its fraction PH3 showed that, except for a few peculiarities, the effects induced were equivalent, suggesting that the highest bioactivity was ascribable to the lightest molecular fraction.