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Journal ArticleDOI

Agricultural uses of plant biostimulants

08 May 2014-Plant and Soil (Springer International Publishing)-Vol. 383, Iss: 1, pp 3-41
TL;DR: There is growing scientific evidence supporting the use of biostimulants as agricultural inputs on diverse plant species, such as increased root growth, enhanced nutrient uptake, and stress tolerance.
Abstract: Plant biostimulants are diverse substances and microorganisms used to enhance plant growth. The global market for biostimulants is projected to increase 12 % per year and reach over $2,200 million by 2018. Despite the growing use of biostimulants in agriculture, many in the scientific community consider biostimulants to be lacking peer-reviewed scientific evaluation. This article describes the emerging definitions of biostimulants and reviews the literature on five categories of biostimulants: i. microbial inoculants, ii. humic acids, iii. fulvic acids, iv. protein hydrolysates and amino acids, and v. seaweed extracts. The large number of publications cited for each category of biostimulants demonstrates that there is growing scientific evidence supporting the use of biostimulants as agricultural inputs on diverse plant species. The cited literature also reveals some commonalities in plant responses to different biostimulants, such as increased root growth, enhanced nutrient uptake, and stress tolerance.

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Citations
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Journal ArticleDOI
23 Nov 2015-Nature
TL;DR: It is argued that the available evidence does not support the formation of large-molecular-size and persistent ‘humic substances’ in soils, and instead soil organic matter is a continuum of progressively decomposing organic compounds.
Abstract: Instead of containing stable and chemically unique ‘humic substances’, as has been widely accepted, soil organic matter is a mixture of progressively decomposing organic compounds; this has broad implications for soil science and its applications. The exchange of nutrients, energy and carbon between soil organic matter, the soil environment, aquatic systems and the atmosphere is important for agricultural productivity, water quality and climate. Long-standing theory suggests that soil organic matter is composed of inherently stable and chemically unique compounds. Here we argue that the available evidence does not support the formation of large-molecular-size and persistent ‘humic substances’ in soils. Instead, soil organic matter is a continuum of progressively decomposing organic compounds. We discuss implications of this view of the nature of soil organic matter for aquatic health, soil carbon–climate interactions and land management. Soil organic matter contains a large portion of the world's carbon and plays an important role in maintaining productive soils and water quality. Nevertheless, a consensus on the nature of soil organic matter is lacking. Johannes Lehmann and Markus Kleber argue that soil organic matter should no longer be seen as large and persistent, chemically unique substances, but as a continuum of progressively decomposing organic compounds.

2,206 citations

Journal ArticleDOI
TL;DR: The legal and regulatory status of biostimulants are described, with a focus on the EU and the US, and the drivers, opportunities and challenges of their market development are outlined.

1,340 citations

Journal ArticleDOI
TL;DR: There is a gap between the mode of action (mechanism) of the PGPR for plant growth and the role of thePGPR as biofertilizer—thus the importance of nano-encapsulation technology in improving the efficacy of PGPR is highlighted.
Abstract: Plant growth promoting rhizobacteria (PGPR) shows an important role in the sustainable agriculture industry. The increasing demand for crop production with a significant reduction of synthetic chemical fertilizers and pesticides use is a big challenge nowadays. The use of PGPR has been proven to be an environmentally sound way of increasing crop yields by facilitating plant growth through either a direct or indirect mechanism. The mechanisms of PGPR include regulating hormonal and nutritional balance, inducing resistance against plant pathogens, and solubilizing nutrients for easy uptake by plants. In addition, PGPR show synergistic and antagonistic interactions with microorganisms within the rhizosphere and beyond in bulk soil, which indirectly boosts plant growth rate. There are many bacteria species that act as PGPR, described in the literature as successful for improving plant growth. However, there is a gap between the mode of action (mechanism) of the PGPR for plant growth and the role of the PGPR as biofertilizer—thus the importance of nano-encapsulation technology in improving the efficacy of PGPR. Hence, this review bridges the gap mentioned and summarizes the mechanism of PGPR as a biofertilizer for agricultural sustainability.

787 citations


Cites background from "Agricultural uses of plant biostimu..."

  • ...In this sense, PGPR may be used to enhance plant health and promote plant growth rate without environmental contamination [5]....

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Journal ArticleDOI
TL;DR: This review suggests that the focus of biostimulant research and validation should be upon proof of efficacy and safety and the determination of a broad mechanism of action, without a requirement for a specific mode of action.
Abstract: This review presents a comprehensive and systematic study of the field of plant biostimulants and considers the fundamental and innovative principles underlying this technology. The elucidation of the biological basis of biostimulant function is a prerequisite for the development of science-based biostimulant industry and sound regulations governing these compounds. The task of defining the biological basis of biostimulants as a class of compounds, however, is made more complex by the diverse sources of biostimulants present in the market, which include bacteria, fungi, seaweeds, higher plants, animals and humate-containing raw materials, and the wide diversity of industrial processes utilized in their preparation. To distinguish biostimulants from the existing legislative product categories we propose the following definition of a biostimulant as ‘a formulated product of biological origin that improves plant productivity as a consequence of the novel or emergent properties of the complex of constituents, and not as a sole consequence of the presence of known essential plant nutrients, plant growth regulators, or plant protective compounds’. The definition provided here is important as it emphasizes the principle that biological function can be positively modulated through application of molecules, or mixtures of molecules, for which an explicit mode of action has not been defined. Given the difficulty in determining a ‘mode of action’ for a biostimulant, and recognizing the need for the market in biostimulants to attain legitimacy, we suggest that the focus of biostimulant research and validation should be upon proof of efficacy and safety and the determination of a broad mechanism of action, without a requirement for the determination of a specific mode of action. While there is a clear commercial imperative to rationalize biostimulants as a discrete class of products, there is also a compelling biological case for the science-based development of, and experimentation with biostimulants in the expectation that this may lead to the identification of novel biological molecules and phenomenon, pathways and processes, that would not have been discovered if the category of biostimulants did not exist, or was not considered legitimate.

698 citations

Journal ArticleDOI
TL;DR: To realize the objective of worldwide sustainable agriculture, it is essential that the many mechanisms employed by PGPB first be thoroughly understood thereby allowing workers to fully harness the potentials of these microbes.
Abstract: The idea of eliminating the use of fertilizers which are sometimes environmentally unsafe is slowly becoming a reality because of the emergence of microorganisms that can serve the same purpose or even do better. Depletion of soil nutrients through leaching into the waterways and causing contamination are some of the negative effects of these chemical fertilizers that prompted the need for suitable alternatives. This brings us to the idea of using microbes that can be developed for use as biological fertilizers (biofertilizers). They are environmentally friendly as they are natural living organisms. They increase crop yield and production and, in addition, in developing countries, they are less expensive compared to chemical fertilizers. These biofertilizers are typically called plant growth-promoting bacteria (PGPB). In addition to PGPB, some fungi have also been demonstrated to promote plant growth. Apart from improving crop yields, some biofertilizers also control various plant pathogens. The objective of worldwide sustainable agriculture is much more likely to be achieved through the widespread use of biofertilizers rather than chemically synthesized fertilizers. However, to realize this objective it is essential that the many mechanisms employed by PGPB first be thoroughly understood thereby allowing workers to fully harness the potentials of these microbes. The present state of our knowledge regarding the fundamental mechanisms employed by PGPB is discussed herein.

592 citations


Cites background from "Agricultural uses of plant biostimu..."

  • ...Today, several PGPB have been commercialized as either biocontrol agents or biofertilizers (Calvo et al. 2014; Reed and Glick 2013)....

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References
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Book
01 Jan 1982
TL;DR: In this paper, the authors present an analysis of organic matter in soil using NMR Spectroscopy and analytical pyrolysis, showing that organic matter is composed of nitrogen and ammonium.
Abstract: Partial table of contents: Organic Matter in Soils: Pools, Distribution, Transformations, and Function. Extraction, Fractionation, and General Chemical Composition of Soil Organic Matter. Organic Forms of Soil Nitrogen. Native Fixed Ammonium and Chemical Reactions of Organic Matter with Ammonia and Nitrite. Organic Phosphorus and Sulfur Compounds. Soil Carbohydrates. Soil Lipids. Biochemistry of the Formation of Humic Substances. Reactive Functional Groups. Structural Components of Humic and Fulvic Acids as Revealed by Degradation Methods. Characterization of Soil Organic Matter by NMR Spectroscopy and Analytical Pyrolysis. Structural Basis of Humic Substances. Spectroscopic Approaches. Colloidal Properties of Humic Substances. Electrochemical and Ion-Exchange Properties of Humic Substances. Organic Matter Reactions Involving Pesticides in Soil. Index.

5,658 citations


"Agricultural uses of plant biostimu..." refers background in this paper

  • ...As stated above, fulvic acid is considered to be the soil organic fraction that is soluble in both alkali and acid (Stevenson 1994)....

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  • ...…i) humic acids, which are soluble in basic media and hence are extracted from soil by dilute alkali and precipitate in acidic media, ii) fulvic acids, which are soluble in both alkali and acid media, and iii) humins, which are not extractable from soil (Stevenson 1994, Berbara and García 2014)....

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  • ...Historically, humic substances were described as refractory, dark-colored heterogeneous organic compounds produced as byproducts of microbial metabolism (Stevenson 1994)....

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Journal ArticleDOI
TL;DR: In this review article, numerous examples of successful application of these compounds to improve plant stress tolerance are presented and a better understanding of the mechanisms of action of exogenously applied GB and proline is expected to aid their effective utilization in crop production in stress environments.

3,847 citations

Book
01 Jan 2006
TL;DR: Animal Models and Therapy, Directed Differentiation and Characterization of Genetically Modified Embryonic Stem Cells for Therapy, and Use of Differentiating Embryonics Stem cells in the Parkinsonian Mouse Model are reviewed.
Abstract: Isolation and Maintenance.- Isolation and Differentiation of Medaka Embryonic Stem Cells.- Maintenance of Chicken Embryonic Stem Cells In Vitro.- Derivation and Culture of Mouse Trophoblast Stem Cells In Vitro.- Derivation, Maintenance, and Characterization of Rat Embryonic Stem Cells In Vitro.- Derivation, Maintenance, and Induction of the Differentiation In Vitro of Equine Embryonic Stem Cells.- Generation and Characterization of Monkey Embryonic Stem Cells.- Derivation and Propagation of Embryonic Stem Cells in Serum- and Feeder-Free Culture.- Signaling in Embryonic Stem Cell Differentiation.- Internal Standards in Differentiating Embryonic Stem Cells In Vitro.- Matrix Assembly, Cell Polarization, and Cell Survival.- Phosphoinositides, Inositol Phosphates, and Phospholipase C in Embryonic Stem Cells.- Cripto Signaling in Differentiating Embryonic Stem Cells.- The Use of Embryonic Stem Cells to Study Hedgehog Signaling.- Transfection and Promoter Analysis in Embryonic Stem Cells.- SAGE Analysis to Identify Embryonic Stem Cell-Predominant Transcripts.- Utilization of Digital Differential Display to Identify Novel Targets of Oct3/4.- Gene Silencing Using RNA Interference in Embryonic Stem Cells.- Genetic Manipulation of Embryonic Stem Cells.- Efficient Transfer of HSV-1 Amplicon Vectors Into Embryonic Stem Cells and Their Derivatives.- Lentiviral Vector-Mediated Gene Transfer in Embryonic Stem Cells.- Use of the Cytomegalovirus Promoter for Transient and Stable Transgene Expression in Mouse Embryonic Stem Cells.- Use of Simian Immunodeficiency Virus Vectors for Simian Embryonic Stem Cells.- Generation of Green Fluorescent Protein-Expressing Monkey Embryonic Stem Cells.- DNA Damage Response and Mutagenesis in Mouse Embryonic Stem Cells.- Ultraviolet-Induced Apoptosis in Embryonic Stem Cells In Vitro.- Use of Embryonic Stem Cells in Pharmacological and Toxicological Screens.- Use of Differentiating Embryonic Stem Cells in Pharmacological Studies.- Embryonic Stem Cells as a Source of Differentiated Neural Cells for Pharmacological Screens.- Use of Murine Embryonic Stem Cells in Embryotoxicity Assays.- Use of Chemical Mutagenesis in Mouse Embryonic Stem Cells.- Epigenetic Analysis of Embryonic Stem Cells.- Nuclear Reprogramming of Somatic Nucleus Hybridized With Embryonic Stem Cells by Electrofusion.- Methylation in Embryonic Stem Cells In Vitro.- Tumor-Like Properties.- Identification of Genes Involved in Tumor-Like Properties of Embryonic Stem Cells.- In Vivo Tumor Formation From Primate Embryonic Stem Cells.- Animal Models and Therapy.- Directed Differentiation and Characterization of Genetically Modified Embryonic Stem Cells for Therapy.- Use of Differentiating Embryonic Stem Cells in the Parkinsonian Mouse Model.

3,665 citations

Journal ArticleDOI
TL;DR: This review focuses on the known, the putative, and the speculative modes-of-action of PGPR, which include fixing N2, increasing the availability of nutrients in the rhizosphere, positively influencing root growth and morphology, and promoting other beneficial plant–microbe symbioses.
Abstract: Numerous species of soil bacteria which flourish in the rhizosphere of plants, but which may grow in, on, or around plant tissues, stimulate plant growth by a plethora of mechanisms. These bacteria are collectively known as PGPR (plant growth promoting rhizobacteria). The search for PGPR and investigation of their modes of action are increasing at a rapid pace as efforts are made to exploit them commercially as biofertilizers. After an initial clarification of the term biofertilizers and the nature of associations between PGPR and plants (i.e., endophytic versus rhizospheric), this review focuses on the known, the putative, and the speculative modes-of-action of PGPR. These modes of action include fixing N2, increasing the availability of nutrients in the rhizosphere, positively influencing root growth and morphology, and promoting other beneficial plant–microbe symbioses. The combination of these modes of actions in PGPR is also addressed, as well as the challenges facing the more widespread utilization of PGPR as biofertilizers.

2,982 citations


"Agricultural uses of plant biostimu..." refers background in this paper

  • ...AMF colonize most agricultural species and have an important role in the P nutrition of many farming systems worldwide, especially in soils with low available P (Thompson 1987)....

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  • ...AMF may also play a role in the protection of roots from heavy metal toxicity by mediating interactions between metals and plant roots (Leyval et al. 1997)....

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  • ...For example, (Wu et al. 2005) reported that plant growth promotion following inoculation of maize (Zea mays) with strains of Bacillus megaterium and Bacillus muciaraglaginous together with AMF was associated with improved nutritional assimilation of plant total N, P, and K. Application of PGPR resulted in a significant increase in N, P, and K uptake as well as root and shoot dry weight in cotton (Gossypium hirsutum) (Egamberdiyeva and Höflich 2004) and wheat (Triticum aestivum) (Shaharoona et al. 2008)....

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  • ...A wide variety of microorganisms such as Pseudomonas spp. and Acinetobacter spp. , Azospirillum ssp., Bacillus spp., and AMF have been reported to increase uptake of Zn (Kohler et al. 2008; Yazdani and Pirdashti 2011), Cu, Mn (Liu et al. 2000), Ca, Mg (Giri and Mukerji 2004; Khan 2005), and S (Banerjee et al. 2006)....

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  • ...Improvement in salt tolerance of maize plants inoculated with AMF (G. mosseae) was related to higher accumulation of soluble sugars in the roots, independent of plant nutritional (P) status (Feng et al. 2002)....

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Journal ArticleDOI
TL;DR: Genetic manipulation of phosphate-solubilizing bacteria to improve their ability to improve plant growth may include cloning genes involved in both mineral and organic phosphate solubilization, followed by their expression in selected rhizobacterial strains.

2,761 citations


"Agricultural uses of plant biostimu..." refers background in this paper

  • ..., Erwinia herbicola, Pseudomonas cepacia, and Burkholderia cepacia (Rodriguez and Fraga 1999)....

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  • ...Organic acids are also responsible for decreasing the pH of the surrounding soil, thereby releasing phosphate ions (Rodriguez and Fraga 1999)....

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  • ...In contrast, gluconic acid seems to be the most frequent organic acid produced by bacteria such as Azospirillum spp. (Rodríguez et al. 2004), Pseudomonas spp., Erwinia herbicola, Pseudomonas cepacia, and Burkholderia cepacia (Rodriguez and Fraga 1999)....

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