Figure - available from: Frontiers in Plant Science
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Physico-chemical features of HA and HA enz. (A) Potentiometric analysis; (B) FTIR; (C) Molecular size distribution by DLS. Hydrodynamic Radius (Rh) values in nm; (D) Molecular size distribution by HPSEC.
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Many studies have shown the capacity of soil humic substances (HS) to improve plant growth in natural ecosystems. This effect involves the activation of different processes within the plant at different coordinated molecular, biochemical, and physiological levels. However, the first event triggered by plant root-HS interaction remains unclear. Some...
Citations
... Additionally, the use of humic and sulfur coordinates for the improvement of oil quality parameters like moisture content, relative density and oil yield in mustard crops. Similar findings were also noticed by (Aranaz et al., 2023;Vikram et al., 2022 andSah et al., 2013) who pointed out that irrigation may dilute the oil content but the use of sulfur improves the oil content by triggering the Acetyl-CoA carboxylase activity (Maurya et al., 2023;Shah et al., 2022 andSingh et al., 2022). ...
Background: Indian mustard, a key oilseed crop in India, is valued for its diverse culinary and health benefits. It faces significant challenges due to a wide range of abiotic stress wherein climate-induced water stress is one of them, which negatively impacts plant population, morpho-physiological growth and biochemical reactions. Thus not only the seed yield but also oil production is declining. Methods: The current study aimed to evaluate the efficacy of humic acid and sulfur on phenology, membrane integrity, lipid peroxidation and oil yield in Brassica juncea under varying water regimes during the Rabi season of 2022-23 at the research farm of Lovely Professional University. The experiment was conducted in a split-plot design with a total of 16 possible combinations of water regimes and chemical treatments which include humic acid and sulfur. Result: The results indicated that most of the traits were noticed as statistically significant for both factors i.e. water regimes and chemical treatments at p=0.05%. Among the treatments, I 3 (Three irrigation) and C 3 (Humic acid + Sulfur) were detected as the most effective treatments in terms of percent increase/decrease, resulting highest value over the respective control. The highest % increase was noticed in the initial plant population, final plant population, days taken for maturity, oil content, the moisture content in oil, chlorophyll a, b, a+b and membrane stability index while the reduction in days taken for branching, days taken for the 50% flowering, relative density and malondialdehyde were noticed in the I 3 and C 3. Thus the findings suggest that the 3 irrigations in combination with humic acid and Sulfur can effectively ameliorate the morpho-physiological growth by increasing the chlorophyll contents, integrity of the cell wall and oil yield in Indian Mustard.
... The functions of humic acid fractions depend on the structures associated with the source materials. Assessments of the structure-activity relationships show that the molecular the conformations of humic acids in aqueous solution are a pivotal factor in influencing their plant-promoting properties (Aranaz et al., 2023). Savy et al. (2020) identified a positive correlation between the methoxyl and aromatic moieties of humic substances and root growth in maize; however, it remains difficult to determine the ultimate efficacy, as the most potent single molecule is hard to identify. ...
The growing demand for sustainable solutions in agriculture, critical for crop productivity and food quality in the face of climate change and reduced agrochemical usage, has brought biostimulants into the spotlight as valuable tools for regenerative agriculture. Due to their diverse biological activities, biostimulants contribute to crop growth, nutrient use efficiency, abiotic resilience, and soil health restoration. Biomolecules, including but not limited to humic substances, protein lysates, phenolics and carbohydrates have undergone thorough investigation because of their demonstrated biostimulant activities. Here, we review the process of discovery and development of extract-based biostimulants and propose a practical step-by-step pipeline starting with biomolecule investigation, followed by extraction and isolation, bioactivity determination, identification of active compound(s), mechanistic elucidation, formulation, and effectiveness assessment. The different steps generate a roadmap that aims to expedite the transfer of interdisciplinary knowledge from laboratory-scale studies to pilot-scale production in practical scenarios aligned with the regulatory framework.
Humic substances (HSs) are a diverse class of natural compounds with no fixed chemical composition, formed from plant and microbial residues through the action of environmental factors and living organisms over many years. Despite extensive research spanning two centuries, the complex and variable nature of HSs' structure remains a subject of scientific inquiry. These substances, notably humic acids, fulvic acids, and humin, play crucial roles in ecological and environmental processes due to their abundant functional groups and resilience to biodegradation. This review explores the intricate structure and properties of HSs, their classification, and their occurrence in nature. It highlights the different models proposed to describe the structural fragments of humic acids, emphasizing their aromatic cores and diverse functional groups. The variability in the molecular weight distribution of HSs, attributed to their polydisperse nature, is also discussed, along with methods used for their determination, such as exclusion chromatography. Furthermore, the elemental and functional compositions of humic acids are examined, detailing their acid-base properties and capacity for heavy metal complexation. The synthesis of HSs from natural sources, such as soil, peat, coal, and artificial processes, is covered, showcasing methods like alkaline extraction and hydrothermal treatment. Recent advancements in artificial humification, including oxidative ammonolysis and Fenton reagent-based oxidation, are reviewed for their potential in producing environmentally friendly humic materials from lignin and waste biomass. The study concludes by underscoring the environmental significance and practical applications of HSs, particularly in agriculture, soil conditioning, and environmental remediation. The diverse properties and synthesis methods of HSs make them promising candidates for sustainable material production and environmental management. Humic acids are versatile compounds beneficial for human health due to their potent antioxidant properties, immune-modulating effects, and support for gastrointestinal health and detoxification. Structurally diverse, they feature groups like carboxyl, phenolic hydroxyl, quinones, ketonic carbonyls, amino, and sulfhydryl, contributing to their stability and amphiphilic nature. In pharmaceutical applications, they show promise for drug delivery, antioxidant therapies, wound healing, antimicrobial actions, and biofilm disruption, underlining their biocompatibility and safety. Key words:
Humic substances (HS) have been defined as a potential plant biostimulant to improve crop yield in a sustainable and environmentally friendly way. Leonardite-suspension concentrate (SC) is a type of HS extracted from lignite that is currently employed to enhance various physiological aspects of plants. However, the different effects between both modes of SC application (root and foliar) are poorly understood, especially on photosynthesis performance. Therefore, this study aimed to investigate the influence of a leonardite-SC-based product (BLACKJAK®), on lettuce growth and photosynthesis efficiency, while comparing both methods of application. For this purpose, four root (R): R1 (0.20 mL/L), R2 (0.40 mL/L), R3 (0.60 mL/L), and R4 (0.80 mL/L), and four foliar: F1 (5.00 mL/L), F2 (7.50 mL/L), F3 (10.00 mL/L), and F4 (12.50 mL/L) BLACKJAK® doses were applied to lettuce plants. Related shoot and root growth parameters, photosynthetic efficiency, and sugar and starch content were assessed in lettuce plants. The results showed that BLACKJAK® improved shoot and root biomass, foliar area, and root length, especially at intermediate doses (R2, R3, F2, and F3), with R3 demonstrating the greatest growth increases. Similarly, the main photosynthetic parameters analyzed (net photosynthetic rate and Rubisco carboxylation efficiency), and the soluble sugars and starch content were improved by the same doses, with R3 showing the best photosynthetic performance. Hence, our study suggests that BLACKJAK® improves lettuce yield and photosynthetic efficiency, particularly with radicular application at R3.
Background
The global population is increasing at a pace that food security has become a major concern. The 20th-century Green Revolution saved billions of people from starvation, but the continuous widespread utilization of pesticides and synthetic fertilizers to boost yields has negatively impacted arable lands, water resources, and the environment. Moreover, the production and use of chemical inputs contribute to global climate change. But this impact could be reduced by replacing synthetic chemical inputs with sustainable resources. A promising and environmentally friendly approach to reduce synthetic chemicals is to incorporate biostimulants from sustainable resources. Humic substances (HSs) are composed of humic, fulvic, and ulmic acids and are the most abundant organic matter on earth. They are well known for their beneficial effects on plant growth and development.
Scope
This review encompasses the most recent findings related to the bio-stimulatory effects of HSs in modulating phytohormone biosynthesis, nutrient uptake and assimilation, primary and secondary metabolism, and tolerance to biotic and abiotic stresses.
Conclusion
Existing evidence shows that HSs have multifaceted actions that are attributed to different functional groups and other bioactive compounds enclosed in their macrostructure. Studies have shown that HSs possess auxin-like properties that alter plant metabolism which results in beneficial effects on plant growth and productivity, such as improved nutrient use efficiency and increased abiotic and biotic stress tolerance. In future studies, delineating the mechanisms that can pave the way to further refine these products and increase their efficacy to amplify beneficial effects is required to develop novel products.