Chitosan as a promising natural compound to enhance potential physiological responses in plant: a review

Chitosan microparticles mitigate nitrogen deficiency in tomato plants

Nitrogen (N) deficiency is one of the most prevalent nutrient deficiencies in plants, and has a significant impact on crop yields. In this work we aimed to develop and evaluate innovative strategies to mitigate N deficiency. We studied the effect of supplementing tomato plants grown under suboptimal N nutrition with chitosan microparticles (CS-MPs) during short- and long-term periods. We observed that the supplementation with CS-MPs prevented the reduction of aerial biomass and the elongation of lateral roots (LR) triggered by N deficiency in tomato plantlets. In addition, levels of nitrates, amino acids and chlorophyll, which decreased drastically upon N deficiency, were either partial or totally restored upon CS-MPs addition to N deficient media. Finally, we showed that CS-MPs treatments increased nitric oxide (NO) levels in root tips and caused the up-regulation of genes involved in N metabolism. Altogether, we suggest that CS-MPs enhance the growth and development of tomato plants under N deficiency through the induction of biochemical and transcriptional responses that lead to increased N metabolism. We propose treatments with CS-MPs as an efficient practice focused to mitigate the nutritional deficiencies in N impoverished soils.

Urea intercalated encapsulated microalgae composite hydrogels for slow-release fertilizers

In agriculture, hydrogels can be addressed for effective operation of water and controlled-release fertilizers. Hydrogels have a significant ability for retaining water and improving nutrient availability in soil, enhancing plant growth while reducing water and fertilizer usage. This work aimed to prepare a hydrogel composite based on microalgae and biopolymers including chitosan and starch for use as a soil conditioner. The hydrogel composite was characterized by FTIR, XRD, and SEM. All hydrogel properties were studied including swelling degree, biodegradability, water-holding capacity, water retention, and re-swelling capacity in soil and water. The urea fertilizer loading and releasing behavior of the prepared hydrogels were investigated. The results revealed that the range of the maximal urea loading was between 99 and 440%, and the kinetics of loading was fitted with Freundlich model. The urea release % exhibited 78-95%, after 30 days, and the kinetics of release was fitted with zero-order, Higuchi, and Korsmeyer-Peppas models. Furthermore, the prepared hydrogels obtained a significant water-holding capacity, after blending soil (50 g) with small amount of hydrogels (1 g), the capacity increased in the range of 99.4-101.5%. In sum, the prepared hydrogels have the potential to be applied as a soil conditioner.

Revolutionizing agriculture with nanotechnology: Innovative approaches in fungal disease management and plant health monitoring

Nanotechnology has emerged as a transformative force in modern agriculture, offering innovative solutions to address challenges related to fungal plant diseases and overall agricultural productivity. Specifically, the antifungal activities of metal, metal oxide, bio-nanoparticles, and polymer nanoparticles were examined, highlighting their unique mechanisms of action against fungal pathogens. Nanoparticles can be used as carriers for fungicides, offering advantages in controlled release, targeted delivery, and reduced environmental toxicity. Nano-pesticides and nano-fertilizers can enhance nutrient uptake, plant health, and disease resistance were explored. The development of nanosensors, especially those utilizing quantum dots and plasmonic nanoparticles, promises early and accurate detection of fungal pathogens, a crucial step in timely disease management. However, concerns about their potential toxic effects on non-target organisms, environmental impacts, and regulatory hurdles underscore the importance of rigorous research and impact assessments. The review concludes by emphasizing the significant prospects of nanotechnology in reshaping the future of agriculture but advocates for a balanced approach that prioritizes safety, sustainability, and environmental stewardship.

Investigating the simultaneous effect of chitosan and arbuscular mycorrhizal fungi on growth, phenolic compounds, PAL enzyme activity and lipid peroxidation in Salvia nemorosa L

Considering the importance of Salvia nemorosa L. in the pharmaceutical and food industries, and also beneficial approaches of arbuscular mycorrhizal fungi (AMF) symbiosis and the use of bioelicitors such as chitosan to improve secondary metabolites, the aim of this study was to evaluate the performance of chitosan on the symbiosis of AMF and the effect of both on the biochemical and phytochemical performance of this plant and finally introduced the best treatment. Two factors were considered for the factorial experiment: AMF with four levels (non-inoculated plants, Funneliformis mosseae, Rhizophagus intraradices and the combination of both), and chitosan with six levels (0, 50, 100, 200, 400 mg L-1 and 1% acetic acid). Four months after treatments, the aerial part and root length, the levels of lipid peroxidation, H2O2, phenylalanine ammonia lyase (PAL) activity, total phenol and flavonoid contents and the main secondary metabolites (rosmarinic acid and quercetin) in the leaves and roots were determined. The flowering stage was observed in R. intraradices treatments and the highest percentage of colonization (78.87%) was observed in the treatment of F. mosseae × 400 mg L-1 chitosan. Furthermore, simultaneous application of chitosan and AMF were more effective than their separate application to induce phenolic compounds accumulation, PAL activity and reduce oxidative compounds. The cluster and principal component analysis based on the measured variables indicated that the treatments could be classified into three clusters. It seems that different treatments in different tissues have different effects. However, in an overview, it can be concluded that 400 mg L-1 chitosan and F. mosseae × R. intraradices showed better results in single and simultaneous applications. The results of this research can be considered in the optimization of this medicinal plant under normal conditions and experiments related to abiotic stresses in the future.

Plant Biostimulant as an Environmentally Friendly Alternative to Modern Agriculture

Ensuring the safety of crop production presents a significant challenge to humanity. Pesticides and fertilizers are commonly used to eliminate external interference and provide nutrients, enabling crops to sustain growth and defense. However, the addition of chemical substances does not meet the environmental standards required for agricultural production. Recently, natural sources such as biostimulants have been found to help plants with growth and defense. The development of biostimulants provides new solutions for agricultural product safety and has become a widely utilized tool in agricultural. The review summarizes the classification of biostimulants, including humic-based biostimulant, protein-based biostimulant, oligosaccharide-based biostimulant, metabolites-based biostimulants, inorganic substance, and microbial inoculant. This review attempts to summarize suitable alternative technology that can address the problems and analyze the current state of biostimulants, summarizes the research mechanisms, and anticipates future technological developments and market trends, which provides comprehensive information for researchers to develop biostimulants.

Different roles of Ca2+ and chitohexose in peanut (Arachis Hypogaea) photosynthetic responses to PAMP-immunity

Background

During active infections, plants prevent further spread of pathogenic microorganisms by inducing the rapid programmed death of cells around the infection point. This phenomenon is called the hypersensitive response and is a common feature of plant immune responses. Plants recognize conserved structures of pathogenic microorganisms, called pathogen-associated molecular patterns (PAMPs), e.g., flagellin 22 (flg22) and chitohexose, which bind to receptors on plant cells to induce various immune-response pathways. Although abiotic stresses are known to alter photosynthesis, the different effects of flg22 and chitohexose, which are involved into PAMP-induced signaling, on photosynthesis needs further study.

Methods

In the present study, we assessed the role of PAMPs in peanut (Arachis hypogaea) photosynthesis, particularly, the interaction between PAMPs and Ca2+ signal transduction pathway.

Results

Both flg22 and chitohexose significantly promoted the expression of the pathogenesis-related genes PR-4 and PR-10, as did Ca2+. We found that Ca2+ is involved in downregulating the photosystem II (PSII) reaction center activity induced by the flg22 immune response, but the role of chitohexose is not obvious. Additionally, Ca2+ significantly reduced the non-photochemical energy dissipation in the flg22- and chitohexose-induced immune response.

Conclusion

These results indicated that flg22 and chitohexose can trigger peanut immune pathways through the Ca2+ signaling pathway, but they differ in their regulation of the activity of the PSII reaction center.

Nanoparticles and biochar with adsorbed plant growth-promoting rhizobacteria alleviate Fusarium wilt damage on tomato and watermelon

The addition of biochars and nanoparticles with adsorbed Azotobacter vinelandii and Bacillus megaterium alleviated damage from Fusarium infection in both tomato (Solanum lycopersicum) and watermelon (Citrullus lanatus) plants. Tomato and watermelon plants were grown in greenhouse for 28 and 30 days (respectively) and were treated with either nanoparticles (chitosan-coated mesoporous silica or nanoclay) or varying biochars (biochar produced by pyrolysis, gasification and pyrogasification). Treatments with nanoparticles and biochars were applied in two variants - with or without adsorbed plant-growth promoting bacteria (PGPR). Chitosan-coated mesoporous silica nanoparticles with adsorbed bacteria increased chlorophyll content in infected tomato and watermelon plants (1.12 times and 1.63 times, respectively) to a greater extent than nanoclay with adsorbed bacteria (1.10 times and 1.38 times, respectively). However, the impact on other endpoints (viability of plant cells, phosphorus and nitrogen content, as well antioxidative status) was species-specific. In all cases, plants treated with adsorbed bacteria responded better than plants without bacteria. For example, the content of antioxidative compounds in diseased watermelon plants increased nearly 46% upon addition of Aries biochar and by approximately 52% upon addition of Aries biochar with adsorbed bacteria. The overall effect on disease suppression was due to combination of the antifungal effects of both nanoparticles (and biochars) and plant-growth promoting bacteria. These findings suggest that nanoparticles or biochars with adsorbed PGPR could be viewed as a novel and sustainable solution for management of Fusarium wilt.

Significance of biopolymer-based hydrogels and their applications in agriculture: a review in perspective of synthesis and their degree of swelling for water holding

Hydrogels are three-dimensional polymer networks that are hydrophilic and capable of retaining a large amount of water. Hydrogels also can act as vehicles for the controlled delivery of active compounds. Bio-polymers are polymers that are derived from natural sources. Hydrogels prepared from biopolymers are considered non-toxic, biocompatible, biodegradable, and cost-effective. Therefore, bio-polymeric hydrogels are being extensively synthesized and used all over the world. Hydrogels based on biopolymers finds important applications in the agricultural field where they are used as soil conditioning agents as they can increase the water retention ability of soil and can act as a carrier of nutrients and other agrochemicals. Hydrogels are also used for the controlled delivery of fertilizer to plants. In this review, bio-polymeric hydrogels based on starch, chitosan, guar gum, gelatin, lignin, and alginate polymer have been discussed in terms of their synthesis method, swelling behavior, and possible agricultural application. The urgency to address water scarcity and the need for sustainable water management in agriculture necessitate the exploration and implementation of innovative solutions. By understanding the synthesis techniques and factors influencing the swelling behavior of these hydrogels, we can unlock their full potential in fostering sustainable agriculture and mitigating the challenges posed by an ever-changing environment.

Chitosan-induced biotic stress tolerance and crosstalk with phytohormones, antioxidants, and other signalling molecules

Several polysaccharides augment plant growth and productivity and galvanise defence against pathogens. Such elicitors have ecological superiority over traditional growth regulators, considering their amplified biocompatibility, biodegradability, bioactivity, non-toxicity, ubiquity, and inexpensiveness. Chitosan is a chitin-derived polysaccharide that has recently been spotlighted among plant scientists. Chitosan supports plant growth and development and protects against microbial entities such as fungi, bacteria, viruses, nematodes, and insects. In this review, we discuss the current knowledge of chitosan's antimicrobial and insecticidal potential with recent updates. These effects are further explored with the possibilities of chitosan's active correspondence with phytohormones such as jasmonic acid (JA), salicylic acid (SA), indole acetic acid (IAA), abscisic acid (ABA), and gibberellic acid (GA). The stress-induced redox shift in cellular organelles could be substantiated by the intricate participation of chitosan with reactive oxygen species (ROS) and antioxidant metabolism, including hydrogen peroxide (H2O2), superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD). Furthermore, we propose how chitosan could be intertwined with cellular signalling through Ca2+, ROS, nitric oxide (NO), transcription factors (TFs), and defensive gene activation.

Application of depolymerized chitosan in crop production: A review

Currently, chitosan (CHT) is well known for its uses, particularly in veterinary and agricultural fields. However, chitosan's uses suffer greatly due to its extremely solid crystalline structure, it is insoluble at pH levels above or equal to 7. This has sped up the process of derivatizing and depolymerizing it into low molecular weight chitosan (LMWCHT). As a result of its diverse physicochemical as well as biological features which include antibacterial activity, non-toxicity, and biodegradability, LMWCHT has evolved into new biomaterials with extremely complex functions. The most important physicochemical and biological property is antibacterial, which has some degree of industrialization today. CHT and LMWCHT have potential due to the antibacterial and plant resistance-inducing properties when applied in crop production. This study has highlighted the many advantages of chitosan derivatives as well as the most recent studies on low molecular weight chitosan applications in crop development.

A Salt-Tolerant Strain of Trichoderma longibrachiatum HL167 Is Effective in Alleviating Salt Stress, Promoting Plant Growth, and Managing Fusarium Wilt Disease in Cowpea

Salt stress is a constraint factor in agricultural production and restricts crops yield and quality. In this study, a salt-tolerant strain of Trichoderma longibrachiatum HL167 was obtained from 64 isolates showing significant salt tolerance and antagonistic activity to Fusarium oxysporum. T. longibrachiatum HL167 inhibited F. oxysporum at a rate of 68.08% in 200 mM NaCl, penetrated F. oxysporum under 200 mM NaCl, and eventually induced F. oxysporum hyphae breaking, according to electron microscope observations. In the pot experiment, pretreatment of cowpea seedlings with T. longibrachiatum HL167 reduced the accumulation level of ROS in tissues and the damage caused by salt stress. Furthermore, in the field experiment, it was discovered that treating cowpea with T. longibrachiatum HL167 before root inoculation with F. oxysporum can successfully prevent and control the development of cowpea Fusarium wilt, with the best control effect reaching 61.54%. Moreover, the application of HL 167 also improved the K+/Na+ ratio of cowpea, alleviated the ion toxicity of salt stress on cowpea, and HL167 was found to effectively colonize the cowpea roots. T. longibrachiatum HL167, which normally survives in saline–alkali environments and has the functions of disease prevention and plant growth promotion capabilities, has important research implications for improving the saline–alkali soil environment and for the sustainable development of green agriculture.

Resistance Inducers for the Protection of Pedunculate Oak (Quercus robur L.) Seedlings against Powdery Mildew Erysiphe alphitoides

Oak powdery mildew caused by Erysiphe alphitoides (Griffon and Maubl.; U. Braun & S. Takam.) is a common disease in European forests. One of the most susceptible species is the pedunculate oak (Quercus robur L.). Presently, a few methods are available to control powdery mildew, e.g., the use of fungicides (e.g., based on citric acid), antagonistic fungi or bacteria, chemical treatments (e.g., sulphur, potassium bicarbonate) or genetic resistance. In our study, we aimed to check the effects of using chitosan derivatives and novel active substances inducing the plants' natural resistance: benzodiathiadiazole (both in neutral and salt form). 84 pedunculate oak seedlings were subjected to the experiment in three treatment variants (plus positive and negative controls). The plants were treated with active substances and inoculated with E. alphitoides. Although the powdery mildew symptoms appeared in all variants, they were manifested mainly by the mycelium in the form of small spots. The experiment indicated that the highest limitation of powdery mildew mycelium was achieved by applying N-methyl-N-methoxyamide-7-carboxybenzo(1,2,3)thiadiazole (BTHWA). The application of BTHWA reduced disease development by 88.9% when compared to the effects of the other variants.

Piperine-loaded nanoparticles incorporated into hyaluronic acid/sodium alginate-based membranes for the treatment of inflammatory skin diseases

Piperine is an alkaloid mostly found in the fruits of several species of the Piper genus, and its anti-inflammatory potential is already known. However, its therapeutic applications still need to be better explored due to the low aqueous solubility of this active. To overcome this drawback, the objective of this work was to evaluate the efficiency of the nanoencapsulation of the compound as well as its incorporation into hyaluronic acid/alginate-based biomembranes. Polymeric nanoparticles composed of Eudragit S100 and Poloxamer 188 were obtained by the nanoprecipitation technique, obtaining spherical nanosized particles with an average diameter of 122.1 ± 2.0 nm, polydispersity index of 0.266, and encapsulation efficiency of 76.2 %. Hyaluronic acid/sodium alginate membranes were then prepared and characterized. Regarding permeation, a slow passage rate was observed until the initial 14 h, when an exponential increase in the recovered drug concentration began to occur. The in vivo assay showed a reduction in inflammation up to 43.6 %, and no cytotoxicity was observed. The results suggested the potential of the system developed for the treatment of inflammatory skin diseases.

Enhancing the Production of Hydrolytic Enzymes in Elicited Tamarillo (Solanum betaceum Cav.) Cell Suspension Cultures

Plant cell suspension cultures are widely used as a tool for analyzing cellular and molecular processes, metabolite synthesis, and differentiation, bypassing the structural complexity of plants. Within the range of approaches used to increase the production of metabolites by plant cells, one of the most recurrent is applying elicitors capable of stimulating metabolic pathways related to defense mechanisms. Previous proteomics analysis of tamarillo cell lines and cell suspension cultures have been used to further characterize and optimize the growth and stress-related metabolite production under in vitro controlled conditions. The main objective of this work was to develop a novel plant-based bioreactor system to produce hydrolytic enzymes using an elicitation approach. Based on effective protocols for tamarillo micropropagation and plant cell suspension culture establishment from induced callus lines, cell growth has been optimized, and enzymatic activity profiles under in vitro controlled conditions characterized. By testing different sucrose concentrations and the effects of two types of biotic elicitors, it was found that 3% (w/v) sucrose concentration in the liquid medium enhanced the production of hydrolytic enzymes. Moreover, casein hydrolysate at 0.5 and 1.5 g/L promoted protein production, whereas yeast extract (0.5 g/L) enhanced glycosidase activity. Meanwhile, chitosan (0.05 and 0.1 g/L) enhanced glycosidases, alkaline phosphates, and protease activities.

Chitin and its derivatives: Functional biopolymers for developing bioproducts for sustainable agriculture-A reality?

Chitinous materials (chitin and its derivatives) are obtained from renewable sources, mainly shellfish waste, having a great potential for the development of bioproducts as alternatives to synthetic agrochemicals. Recent studies have provided evidence that the use of these biopolymers can help control postharvest diseases, increase the content of nutrients available to plants, and elicit positive metabolic changes that lead to higher plant resistance against pathogens. However, agrochemicals are still widely and intensively used in agriculture. This perspective addresses the gap in knowledge and innovation to make bioproducts based on chitinous materials more competitive in the market. It also provides the readers with background to understand why these products are scarcely used and the aspects that need to be considered to increase their use. Finally, information on the development and commercialization of agricultural bioproducts containing chitin or its derivatives in the Chilean market is also provided.

Chitosan nanoparticles improve physiological and biochemical responses of Salvia abrotanoides (Kar.) under drought stress

BACKGROUND

The use of organic nanoparticles to improve drought resistance and water demand characteristics in plants seems to be a promising eco-friendly strategy for water resource management in arid and semi-arid areas. This study aimed to investigate the effect of chitosan nanoparticles (CNPs) (0, 30, 60 and 90 ppm) on some physiological, biochemical, and anatomical responses of Salvia abrotanoides under multiple irrigation regimes (30% (severe), 50% (medium) and 100% (control) field capacity).

RESULTS

The results showed that drought stress decreases almost all biochemical parameters. However, foliar application of CNPs mitigated the effects caused by drought stress. This elicitor decreased electrolyte conductivity (35%), but improved relative water content (12.65%), total chlorophyll (63%), carotenoids (68%), phenol (23.1%), flavonoid (36.4%), soluble sugar (58%), proline (49%), protein (45.2%) in S. abrotanoides plants compared to the control (CNPs = 0). Furthermore, the activity of antioxidant enzymes superoxide dismutase (86%), polyphenol oxidase (72.8%), and guaiacol peroxidase (75.7%) were enhanced after CNPs treatment to reduce the effects of water deficit. Also, the CNPs led to an increase in stomatal density (5.2 and 6.6%) while decreasing stomatal aperture size (50 and 25%) and semi-closed stomata (26 and 53%) in leaves.

CONCLUSION

The findings show that CNPs not only can considerably reduce water requirement of S. abrotanoides but also are able to enhance the drought tolerance ability of this plant particularly in drought-prone areas.

Eco-friendly application of nano-chitosan for controlling potato and tomato bacterial wilt

Bacterial wilt is one of the main diseases of Solanum spp., which caused by Ralstonia solanacearum (RS), formerly known as Pseudomonas solanacearum. Different concentrations of chitosan nanoparticles have been evaluated as one of the alternative methods of disease management in vitro and in vivo to reduce the risks of pesticide residues. Results in vitro experiment indicated that RS5 isolate was the most virulence one compared to RS1 and RS3. Increasing concentration of nano-chitosan, lead to increase inhibition zone, and this was observed at higher concentrations (100 and 200 µg/ml). In vivo results showed the highest concentration of spraying chitosan nanoparticles increase percentage reduction of disease incidence and severity, in effected potato and tomato plants. Recorded data of disease incidence and severity in treated potato plants were 78.93% and 71.85%, while on tomato plants were 81.64% and 77.63%, respectively compared to untreated infected potato plants were recorded 15.38%, 20.87%, and tomato plants were 20.98% and 28.64%. Results also revealed that 100 µg/ml of chitosan nanoparticles the lowest treatments used as soil amended curative treatments led to incease percentage reduction of disease incidence and severity, respectively on potato and tomato plants, but less than preventive treatment. The results registered that on potato plant were 54.93% and 52.65%, whilst recorded on tomato plants were 59.93% and 56.74%. Transmission electron microscopy (TEM) micrpgraphs illustrated that morphological of healthy R. solanacearum cells were undesirably stained with uranyl. The electron-dense uranyl acetate dye was limited to the cell surface slightly than the cytoplasm, which designated the integrity of the cell film of healthy cells. While bacterial cells treated with nano-chitosan, showed modification in the external shape, such as lysis of the cell wall and loss of cell flagella. Also, the result of using Random amplified polymorphic DNA (RAPD)-PCR observed that differences in treated Ralstonia solanancearum genotype by nano-chitosan compared to the genotype of the same untreated isolate.

Synthesis of γ-Aminobutyric Acid-Modified Chitooligosaccharide Derivative and Enhancing Salt Resistance of Wheat Seedlings

Salinity is one of the major abiotic stresses limiting crop growth and productivity worldwide. Salt stress during germination degenerates crop establishment and declines yield in wheat, therefore alleviating the damage of salt stress to wheat seedlings is crucial. Chitooligosaccharide (COS) was grafted with γ-aminobutyric acid based on the idea of bioactive molecular splicing, and the differences in salt resistance before and after grafting were compared. The expected derivative was successfully synthesized and exhibited better salt resistance-inducing activity than the raw materials. By activating antioxidant enzymes such as superoxide dismutases (SOD), catalase (CAT) and phenylalanine ammonia-lyase (PAL) and subsequently eliminating reactive oxygen species (ROS) in a timely manner, the rate of O⁻₂ production and H₂O₂ content of wheat seedlings were reduced, and the dynamic balance of free radical metabolism in the plant body was maintained. A significantly reduced MDA content, reduced relative permeability of the cell membrane, and decreased degree of damage to the cell membrane were observed. A significant increase in the content of soluble sugar, maintenance of osmotic regulation and the stability of the cell membrane structure, effective reduction in the salt stress-induced damage to wheat, and the induction of wheat seedling growth were also observed, thereby improving the salt tolerance of wheat seedlings.

Protective, Biostimulating, and Eliciting Effects of Chitosan and Its Derivatives on Crop Plants

Chitosan is a biodegradable and biocompatible polysaccharide obtained by partial deacetylation of chitin. This polymer has been gaining increasing popularity due to its natural origin, favorable physicochemical properties, and multidirectional bioactivity. In agriculture, the greatest hopes are raised by the possibility of using chitosan as a biostimulant, a plant protection product, an elicitor, or an agent to increase the storage stability of plant raw materials. The most important properties of chitosan include induction of plant defense mechanisms and regulation of metabolic processes. Additionally, it has antifungal, antibacterial, antiviral, and antioxidant activity. The effectiveness of chitosan interactions is determined by its origin, deacetylation degree and acetylation pattern, molecular weight, type of chemical modifications, pH, concentration, and solubility. There is a need to conduct research on alternative sources of chitosan, extraction methods, optimization of physicochemical properties, and commercial implementation of scientific progress outcomes in this field. Moreover, studies are necessary to assess the bioactivity and toxicity of chitosan nanoparticles and chitosan conjugates with other substances and to evaluate the consequences of the large-scale use thereof. This review presents the unique properties of chitosan and its derivatives that have the greatest importance for plant production and yield quality as well as the benefits and limitations of their application.

Priming with copper-chitosan nanoparticles elicit tolerance against PEG-induced hyperosmotic stress and salinity in wheat

In this study Cu-chitosan nanoparticles (Cu-CNP) have been employed as eco-friendly and safer priming agents to induce salt and PEG-induced hyperosmotic stress tolerance in wheat seedlings. Seed priming is a facile on-farm stress management technique that requires a little amount of priming agent and minimizes the eco-toxicological effects on soil fertility. The wheat seeds were primed with 0.12% and 0.16% Cu-CNP for eight hours and were allowed to germinate under normal, PEG-induced hyperosmotic stress (15% PEG-6000  – 3.0 Mpa) and salt stress (150 mM). For comparison, non-primed and hydro-primed seeds were also allowed to germinate as control under the same conditions. The biochemical analyses suggested the priming treatments enhanced the POD activity under salt stress but it was decreased under PEG-induced hyperosmotic stress. Priming with 0.12% Cu-CNP induced a significant increase in CAT while the opposite effect was observed in 0.16% treated seedling under stress and non-stress conditions. Both priming treatments did not allow the over-expression of SOD under both stress conditions. The total phenolic contents were also decreased significantly under all conditions. Except for priming with 0.16% Cu-CNP under PEG-induced hyperosmotic stress, a suppression in MDA was observed under both stress conditions. Surprisingly, the Cu-CNP priming induced a significant increase in β-carotenoids, total carotenoids, chlorophyll a, b and total chlorophyll under normal and stress conditions. In conclusion, the controlled expression of enzymatic antioxidants, low contents of non-enzymatic antioxidants and suppression of MDA mirror the stress mitigating role of Cu-CNP against PEG-induced hyperosmotic stress and salinity. The stress-insulating potential has also been reinforced by the enhanced production of plant and photosynthetic pigments. All these priming-induced biochemical changes produced positive effects on growth and germinating parameters in wheat seedlings under PEG-induced hyperosmotic stress as well as salinity.

Impact of Chitosan on the Mechanical Stability of Soils

Chitosan is becoming increasingly applied in agriculture, mostly as a powder, however little is known about its effect on soil mechanical properties. Uniaxial compression test was performed for cylindrical soil aggregates prepared from four soils of various properties (very acidic Podzol, acidic Arenosol, neutral Fluvisol and alkaline Umbrisol) containing different proportions of two kinds of chitosan (CS1 of higher molecular mass and lower deacetylation degree, and CS2 of lower molecular mass and higher deacetylation degree), pretreated with 1 and 10 wetting–drying cycles. In most cases increasing chitosan rates successively decreased the mechanical stability of soils that was accompanied by a tendential increase in soil porosity. In one case (Fluvisol treated with CS2) the porosity decreased and mechanical stability increased with increasing chitosan dose. The behavior of acidic soils (Podzol and Arenosol) treated with CS2, differed from the other soils: after an initial decrease, the strength of aggregates increased with increasing chitosan amendment, despite the porosity consequently decreasing. After 10 wetting–drying cycles, the strength of the aggregates of acidic soils appeared to increase while it decreased for neutral and alkaline soils. Possible mechanisms of soil–chitosan interactions affecting mechanical strength are discussed and linked with soil water stability and wettability.

Biochar and Chitosan Regulate Antioxidant Defense and Methylglyoxal Detoxification Systems and Enhance Salt Tolerance in Jute (Corchorus olitorius L.)

We investigated the role of biochar and chitosan in mitigating salt stress in jute (Corchorus olitorius L. cv. O-9897) by exposing twenty-day-old seedlings to three doses of salt (50, 100, and 150 mM NaCl). Biochar was pre-mixed with the soil at 2.0 g kg⁻¹ soil, and chitosan-100 was applied through irrigation at 100 mg L⁻¹. Exposure to salt stress notably increased lipid peroxidation, hydrogen peroxide content, superoxide radical levels, electrolyte leakage, lipoxygenase activity, and methylglyoxal content, indicating oxidative damage in the jute plants. Consequently, the salt-stressed plants showed reduced growth, biomass accumulation, and disrupted water balance. A profound increase in proline content was observed in response to salt stress. Biochar and chitosan supplementation significantly mitigated the deleterious effects of salt stress in jute by stimulating both non-enzymatic (e.g., ascorbate and glutathione) and enzymatic (e.g., ascorbate peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase, glutathione reductase superoxide dismutase, catalase, peroxidase, glutathione S-transferase, glutathione peroxidase) antioxidant systems and enhancing glyoxalase enzyme activities (glyoxalase I and glyoxalase II) to ameliorate reactive oxygen species damage and methylglyoxal toxicity, respectively. Biochar and chitosan supplementation increased oxidative stress tolerance and improved the growth and physiology of salt-affected jute plants, while also significantly reducing Na⁺ accumulation and ionic toxicity and decreasing the Na⁺/K⁺ ratio. These findings support a protective role of biochar and chitosan against salt-induced damage in jute plants.

A Pivotal Role of Chitosan Nanoparticles in Enhancing the Essential Oil Productivity and Antioxidant Capacity in Matricaria chamomilla L

Chitosan is a biopolymer with several biological and agricultural applications. Recently, development of chitosan nanoparticles (CSNPs) adds additional value by further using it as an eco-friendly biostimulant. Therefore, the impact of CSNPs foliar application on the growth, essential oil productivity and antioxidant capacity of chamomile was investigated. Treatments comprised 0, 100, 200, 300 and 400 mg L−1 of CSNPs applied to plants as a foliar spray. CSNPs foliar application improved the growth and productivity of chamomile plants. Relative to the control, the flower yield was increased by 52.10 and 55.74% while the essential oil percentage was increased by 57.14 and 47.06% due to CSNPs at 300 mg L−1 during the two seasons of study. Moreover, CSNPs enhanced the photosynthetic pigments, total soluble sugars and N, P and K percentages. Interestingly, CSNPs increased the antioxidant capacity as measured by total phenolics and the antioxidant activity (DPPH). Collectively, it is suggested that CSNPs might be a promising eco-friendly bio-stimulant and it could be an alternative strategy to improve the productivity, quality and decrease the production cost of chamomile and possibly some other medicinal species.

Electron Beam Irradiated Chitosan elicits enhanced antioxidant properties combating resistance to Purple Blotch Disease (Alternaria porri) in Onion (Allium cepa)

PURPOSE

This study was carried out to assess the effect of irradiated chitosan as an elicitor on the biochemical traits associated with resistance to purple blotch disease in onion.

MATERIALS AND METHODS

Chitosan was electron beam irradiated at 100 kGy dose to obtain low molecular weight chitosan. Irradiated chitosan at 20 and 0.04% concentration and different time intervals was used as a biological elicitor cum antimicrobial agent against purple blotch disease in onion. Field grown onion (Variety Basanvant 780) plants were foliar sprayed with irradiated chitosan and the biochemical responses were monitored using parameters namely chlorophylls, carotenoids, antioxidant enzymes, phenols, and antifungal enzyme β-1,3 Glucanase using standard methods.

RESULTS

Compared to control treatment, a positive correlation with irradiated chitosan treatment was observed for an increase in β-1,3-glucanase, peroxidase activity, and contents of total phenolics, chlorophylls, and carotenoids, which cumulatively contributed to resistance response against the purple blotch disease. Irradiated chitosan (0.04%) treated onion plants at 30, 45, and 60 DAT showed a higher total phenolics, β-1,3-glucanase activity, and peroxidase activity besides enhanced antioxidant properties.

CONCLUSION

The results suggest that irradiated chitosan has elicited resistance responses against purple blotch disease in onion. The increased production of antioxidant metabolites may provide value addition to onion as a food commodity.

Biostimulants for the Regulation of Reactive Oxygen Species Metabolism in Plants under Abiotic Stress

Global food security for a growing population with finite resources is often challenged by multiple, simultaneously occurring on-farm abiotic stresses (i.e., drought, salinity, low and high temperature, waterlogging, metal toxicity, etc.) due to climatic uncertainties and variability. Breeding for multiple stress tolerance is a long-term solution, though developing multiple-stress-tolerant crop varieties is still a challenge. Generation of reactive oxygen species in plant cells is a common response under diverse multiple abiotic stresses which play dual role of signaling molecules or damaging agents depending on concentration. Thus, a delicate balance of reactive oxygen species generation under stress may improve crop health, which depends on the natural antioxidant defense system of the plants. Biostimulants represent a promising type of environment-friendly formulation based on natural products that are frequently used exogenously to enhance abiotic stress tolerance. In this review, we illustrate the potential of diverse biostimulants on the activity of the antioxidant defense system of major crop plants under stress conditions and their other roles in the management of abiotic stresses. Biostimulants have the potential to overcome oxidative stress, though their wider applicability is tightly regulated by dose, crop growth stage, variety and type of biostimulants. However, these limitations can be overcome with the understanding of biostimulants’ interaction with ROS signaling and the antioxidant defense system of the plants.

A Green Nanostructured Pesticide to Control Tomato Bacterial Speck Disease

Bacterial speck disease, caused by Pseudomonas syringae pv. tomato (Pst), is one of the most pervasive biological adversities in tomato cultivation, in both industrial and in table varieties. In this work synthesis, biochemical and antibacterial properties of a novel organic nanostructured pesticide composed of chitosan hydrochloride (CH) as active ingredient, cellulose nanocrystals (CNC) as nanocarriers and starch as excipient were evaluated. In order to study the possibility of delivering CH, the effects of two different types of starches, extracted from a high amylose bread wheat (high amylose starch-HA Starch) and from a control genotype (standard starch-St Starch), were investigated. Nanostructured microparticles (NMP) were obtained through the spray-drying technique, revealing a CH loading capacity proximal to 50%, with a CH release of 30% for CH-CNC-St Starch NMP and 50% for CH-CNC-HA Starch NMP after 24 h. Both NMP were able to inhibit bacterial growth in vitro when used at 1% w/v. Moreover, no negative effects on vegetative growth were recorded when NMP were foliar applied on tomato plants. Proposed nanostructured pesticides showed the capability of diminishing Pst epiphytical survival during time, decreasing disease incidence and severity (from 45% to 49%), with results comparable to one of the most used cupric salt (hydroxide), pointing out the potential use of CH-CNC-Starch NMP as a sustainable and innovative ally in Pst control strategies.

Chitosan stimulates secondary metabolite production and nutrient uptake in medicinal plant Dracocephalum kotschyi

BACKGROUND

A wide variety of secondary metabolites are synthesized from primary metabolites by plants which have a vast range in pharmaceutical, food additive and industrial applications. In recent years, the use of elicitors has opened a novel approach for the production of secondary metabolite compounds. Dracocephalum kotschyi is a valuable herb due to pharmaceutical compounds like rosmarinic acid, quercetin and apigenin. In the current study, foliar application of chitosan (0, 100, 400 mg L-1 ) as an elicitor was used.

RESULTS

After chitosan treatment, the amounts of hydrogen peroxide (H2 O2 ) increased and the plant was able to increase the activities of enzymatic (guaiacol peroxidase, catalase and phenylalanine ammonium lyase) and non-enzymatic (total phenols and flavonoids) defensive metabolites. Also, foliar spray of chitosan promoted nutrient absorption which led to the accumulation of macroelements in the plant.

CONCLUSIONS

Chitosan was found to be a very effective elicitor for improving rosmarinic acid and quercetin content (up to 13-fold). Also, the content of apigenin (anticancer flavonoid) showed 16-fold enhancement compared to the control. Therefore, the treatment of D. kotschyi leaves with chitosan caused a very large increase in the induction and production of important pharmaceutical compounds such as rosmarinic acid and quercetin. © 2020 Society of Chemical Industry.

Biocontrol Agents: Toolbox for the Screening of Weapons against Mycotoxigenic Fusarium

The aim of this study was to develop a set of experiments to screen and decipher the mechanisms of biocontrol agents (BCAs), isolated from commercial formulation, against two major mycotoxigenic fungi in cereals, Fusarium graminearum and Fusarium verticillioides. These two phytopathogens produce mycotoxins harmful to human and animal health and are responsible for the massive use of pesticides, for the protection of cereals. It is therefore essential to better understand the mechanisms of action of alternative control strategies such as the use of BCAs in order to optimize their applications. The early and late stages of interaction between BCAs and pathogens were investigated from germination of spores to the effects on perithecia (survival form of pathogen). The analysis of antagonist activities of BCAs revealed different strategies of biocontrol where chronological, process combination and specialization aspects of interactions are discussed. Streptomyces griseoviridis main strategy is based on antibiosis with the secretion of several compounds with anti-fungal and anti-germination activity, but also a mixture of hydrolytic enzymes to attack pathogens, which compensates for an important deficit in terms of spatial colonization capacity. It has good abilities in terms of nutritional competition. Trichoderma asperellum is capable of activating a very wide range of defenses and attacks combining the synthesis of various antifungal compounds (metabolite, enzymes, VOCs), with different targets (spores, mycelium, mycotoxins), and direct action by mycoparasitism and mycophagy. Concerning Pythium oligandrum, its efficiency is mainly due to its strong capacity to colonize the environment, with a direct action via microbial predation, stimulation of its reproduction at the contact of pathogens and the reduction of perithecia formation.

Differential expression of bio-active metabolites produced by chitosan polymers-based Bacillus amyloliquefaciens fermentation

Bacillus amyloliquefaciens strain PPL shows a potential for the control of phytopathogenic fungi. In the present study, upon growing the strain PPL on various forms of chitosan (0.5 % powder, 0.1 % soluble, and 0.15 % colloidal) as the carbon source, the antifungal activity on tomato Fusarium wilt correlated with the activity of chitosanase and β-1,3-glucanase. The colloidal substrate-based strain PPL fermentation displayed the highest degree of spore germination inhibition (79.5 %) and biocontrol efficiency (76.0 %) in tomato by increased biofilm formation. The colloidal culture upregulated the expression of chitosanase gene (5.9-fold), and the powder attributed to the expression of cyclic lipopeptides-genes (2.5-5.7 fold). Moreover, the three chitosan cultures induced the morphological changes of Fusarium oxysporum. These results suggest that the choice of growth substrate synergistically affects the production of secondary metabolites by PPL strain, and consequently its antifungal activity.

Chemical and physical Chitosan modification for designing enzymatic industrial biocatalysts: How to choose the best strategy?

Chitosan is one of the most abundant natural polymer worldwide, and due to its inherent characteristics, its use in industrial processes has been extensively explored. Because it is biodegradable, biocompatible, non-toxic, hydrophilic, cheap, and has good physical-chemical stability, it is seen as an excellent alternative for the replacement of synthetic materials in the search for more sustainable production methodologies. Thus being, a possible biotechnological application of Chitosan is as a direct support for enzyme immobilization. However, its applicability is quite specific, and to overcome this issue, alternative pretreatments are required, such as chemical and physical modifications to its structure, enabling its use in a wider array of applications. This review aims to present the topic in detail, by exploring and discussing methods of employment of Chitosan in enzymatic immobilization processes with various enzymes, presenting its advantages and disadvantages, as well as listing possible chemical modifications and combinations with other compounds for formulating an ideal support for this purpose. First, we will present Chitosan emphasizing its characteristics that allow its use as enzyme support. Furthermore, we will discuss possible physicochemical modifications that can be made to Chitosan, mentioning the improvements obtained in each process. These discussions will enable a comprehensive comparison between, and an informed choice of, the best technologies concerning enzyme immobilization and the application conditions of the biocatalyst.

A vital role of chitosan nanoparticles in improvisation the drought stress tolerance in Catharanthus roseus (L.) through biochemical and gene expression modulation

Drought is a main abiotic stress that restricts plant growth and development. The increased global demand of anti-cancer alkaloids extracted from periwinkle (Catharanthus roseus) is mainly related to plant growth and development, which are severely affected by drought. Chitosan nanoparticles (CSNPs) have been used to boost plant growth and defense mechanism, however their impact to alleviate drought stress of C. roseus has not been investigated yet. In this study, control and stressed plants (100 and 50% of field capacity [FC], respectively) were subjected to CSNPs application at 1%. Drought stress considerably reduced plant growth, relative water content (RWC), stomatal conductance and total chlorophyll; however, CSNPs mitigated these effects. They enhanced proline accumulation and the activity of catalase (CAT) and ascorbate peroxidase (APX) with possible mitigation of drought-induced oxidative stress. Therefore, they reduced H₂O₂ and malondialdehyde (MDA) accumulation, and eventually preserved membrane integrity. Drought stress increased alkaloid accumulation, and further increase was observed with the application of CSNPs. High alkaloid content was associated with induced gene expression of strictosidine synthase (STR), deacetylvindoline-4-O-acetyltransferase (DAT), peroxidase 1 (PRX1) and geissoschizine synthase (GS) up to 5.6 folds under drought stress, but more accumulation was noticed with the application of CSNPs. Overall, this study is the first on using CSNPs to mitigate drought stress of C. roseus by inducing the antioxidant potential and gene expression of alkaloid biosynthesis.

Current trends and challenges in the synthesis and applications of chitosan-based nanocomposites for plants: A review

Chitosan, a low-cost and multipurpose polymer with numerous desired physicochemical and biological properties has been tested for various applications in agriculture, pharmacy, and biomedicine industries. The availability of functional groups along the backbone makes chitosan readily available for other polymers and metal ions to form bio-nanocomposites. Different types of chitosan-based nanocomposites have been designed and tested for the enhancement of chitosan efficiency and ultimately widening the application areas of chitosan in plants. These nanocomposites serve different purposes such as eliciting plant's defence systems against different threats (pathogen attack), antimicrobial agent against bacteria, fungi and viruses, enhancement of nutrient uptake by plants, control release of micro/macronutrients, fungicides and herbicides. In this review, an extensive outlook has been provided (mainly in the last five years) to recent trends and advances in the fabrication and application of chitosan-based composites. Finally, current challenges and future development opportunities of chitosan-based nanocomposites for plants are discussed.

Transcriptomics of Biostimulation of Plants Under Abiotic Stress

Plant biostimulants are compounds, living microorganisms, or their constituent parts that alter plant development programs. The impact of biostimulants is manifested in several ways: via morphological, physiological, biochemical, epigenomic, proteomic, and transcriptomic changes. For each of these, a response and alteration occur, and these alterations in turn improve metabolic and adaptive performance in the environment. Many studies have been conducted on the effects of different biotic and abiotic stimulants on plants, including many crop species. However, as far as we know, there are no reviews available that describe the impact of biostimulants for a specific field such as transcriptomics, which is the objective of this review. For the commercial registration process of products for agricultural use, it is necessary to distinguish the specific impact of biostimulants from that of other legal categories of products used in agriculture, such as fertilizers and plant hormones. For the chemical or biological classification of biostimulants, the classification is seen as a complex issue, given the great diversity of compounds and organisms that cause biostimulation. However, with an approach focused on the impact on a particular field such as transcriptomics, it is perhaps possible to obtain a criterion that allows biostimulants to be grouped considering their effects on living systems, as well as the overlap of the impact on metabolism, physiology, and morphology occurring between fertilizers, hormones, and biostimulants.

Pure Organic Active Compounds Against Abiotic Stress: A Biostimulant Overview

Biostimulants (BSs) are probably one of the most promising alternatives nowadays to cope with yield losses caused by plant stress, which are intensified by climate change. Biostimulants comprise many different compounds with positive effects on plants, excluding pesticides and chemical fertilisers. Usually mixtures such as lixiviates from proteins or algal extracts have been used, but currently companies are interested in more specific compounds that are capable of increasing tolerance against abiotic stress. Individual application of a pure active compound offers researchers the opportunity to better standarise formulations, learn more about the plant defence process itself and assist the agrochemical industry in the development of new products. This review attempts to summarise the state of the art regarding various families of organic compounds and their mode/mechanism of action as BSs, and how they can help maximise agricultural yields under stress conditions aggravated by climate change.

The Influence of Trichoderma harzianum Rifai T-22 and Other Biostimulants on Rhizosphere Beneficial Microorganisms of Carrot

The principles of good agricultural and horticultural practice, which consider both giving environmental protection and high yielding of plants, require modern cultivation methods. Modern cultivation of horticultural plants uses, for example, cover crops, living mulches, plant growth-promoting microorganisms (PGPMs), plant growth regulators (PGRs) and other biostimulants protecting the soil against degradation and plants against phytopathogens and stress. The purpose of field and laboratory studies was to determine the effect of Trianum P (containing Trichoderma harzianum Rifai T-22 spores), Beta-Chikol (a.s.—chitosan), Timorex Gold 24 EC (based on tea tree oil) and fungicide Zaprawa Nasienna T 75 DS/WS (a.s.—tiuram 75%) on the health of carrot (Daucus carota L.) plants and the microorganism population in the rhizosphere of this plant. Moreover, the antagonistic effect of rhizosphere fungi on selected carrot fungal pathogens was determined. Laboratory mycological analysis allowed one to determine the qualitative and quantitative composition of fungi colonizing the underground parts of carrot plants. In addition, the total population of fungi and bacteria was determined (including Bacillus sp. and Pseudomonas sp.) based on the microbiological analysis of the rhizosphere soil. The application of the plant growth-promoting fungus (Trichoderma harzianum T-22), chitosan and tea tree oil positively influenced the growth, development and health status of carrot plants. T. harzianum T-22, chitosan and fungicide most effectively protected carrots against infection by soil-borne fungi from the genus Alternaria, Fusarium, Haematonectria, Sclerotinia and Rhizoctonia. The rhizosphere population of Bacillus sp. and Pseudomonas sp. in the treatments with Trianum P or Zaprawa Nasienna T 75 DS/WS was bigger than in the other experimental treatments. A reverse relationship was observed in the population of rhizosphere fungi. T. harzianum T-22, chitosan and tea tree oil promoted the growth of antagonistic fungi (Albifimbria sp., Clonostachys sp., Penicillium sp., Talaromyces sp. and Trichoderma sp.) in the carrot rhizosphere. Antagonistic activity of these fungi towards Alternaria dauci, Alternaria radicina, Sclerotiniasclerotiorum and Rhizoctonia solani was higher after the application of the preparations compared to control. Consequently, Trianum P, Beta-Chikol and Timorex Gold 24 EC can be recommended as plant biostimulants in ecological agricultural production, including Daucus carota cultivation.

Chitosan Hydrochloride Decreases Fusarium graminearum Growth and Virulence and Boosts Growth, Development and Systemic Acquired Resistance in Two Durum Wheat Genotypes

Fusarium head blight (FHB) is a devastating disease for cereals. FHB is managed by fungicides at anthesis, but their efficacy is variable. Conventional fungicides accumulate in the soil and are dangerous for animal and human health. This study assayed the antifungal ability of chitosan hydrochloride against Fusarium graminearum. Chitosan reduced F. graminearum growth and downregulated the transcript of the major genes involved in the cell growth, respiration, virulence, and trichothecenes biosynthesis. Chitosan promoted the germination rate, the root and coleoptile development, and the nitrogen balance index in two durum wheat genotypes, Marco Aurelio (FHB-susceptible) and DBC480 (FHB-resistant). Chitosan reduced FHB severity when applied on spikes or on the flag leaves. FHB severity in DBC480 was of 6% at 21 dpi after chitosan treatments compared to F. graminearum inoculated control (20%). The elicitor-like property of chitosan was confirmed by the up-regulation of TaPAL, TaPR1 and TaPR2 (around 3-fold). Chitosan decreased the fungal spread and mycotoxins accumulation. This study demonstrated that the non-toxic chitosan is a powerful molecule with the potential to replace the conventional fungicides. The combination of a moderately resistant genotype (DBC480) with a sustainable compound (chitosan) will open new frontiers for the reduction of conventional compounds in agriculture.

Coumarin-Containing Light-Responsive Carboxymethyl Chitosan Micelles as Nanocarriers for Controlled Release of Pesticide

Currently, controlled release formulations (CRFs) of pesticides in response to biotic and/or abiotic stimuli have shown great potential for providing “on-demand” smart release of loaded active ingredients. In this study, amphiphilic biopolymers were prepared by introducing hydrophobic (7-diethylaminocoumarin-4-yl)methyl succinate (DEACMS) onto the main chain of hydrophilic carboxymethylchitosan (CMCS) via the formation of amide bonds which were able to self-assemble into spherical micelles in aqueous media and were utilized as light-responsive nanocarriers for the controlled release of pesticides. FTIR and NMR characterizations confirmed the successful synthesis of the CMCS-DEACMS conjugate. The critical micelle concentration (CMC) decreased with the increase in the substitution of DEACMS on CMCS, which ranged from 0.013 to 0.042 mg/mL. Upon irradiation under simulated sunlight, the hydrodynamic diameter, morphology, photophysical properties and photolysis were researched by means of dynamic light scattering (DLS), transmission electron microscopy (TEM), UV-vis absorption spectroscopy and fluorescence spectroscopy. Moreover, 2,4-dichlorophenoxyacetic acid (2,4-D) was used as a model pesticide and encapsulated into the CMCS-DEACMS micelles. In these micelle formulations, the release of 2,4-D was promoted upon simulated sunlight irradiation, during which the coumarin moieties were cleaved from the CMCS backbone, resulting in a shift of the hydrophilic–hydrophobic balance and destabilization of the micelles. Additionally, bioassay studies suggested that this 2,4-D contained which micelles showed good bioactivity on the target plant without harming the nontarget plant. Thereby, the light-responsive CMCS-DEACMS micelles bearing photocleavable coumarin moieties provide a smart delivery platform for agrochemicals.

Chlorophyll Fluorescence Parameters and Antioxidant Defense System Can Display Salt Tolerance of Salt Acclimated Sweet Pepper Plants Treated with Chitosan and Plant Growth Promoting Rhizobacteria

Salinity stress deleteriously affects the growth and yield of many plants. Plant growth promoting rhizobacteria (PGPR) and chitosan both play an important role in combating salinity stress and improving plant growth under adverse environmental conditions. The present study aimed to evaluate the impacts of PGPR and chitosan on the growth of sweet pepper plant grown under different salinity regimes. For this purpose, two pot experiments were conducted in 2019 and 2020 to evaluate the role of PGPR (Bacillus thuringiensis MH161336 106–8 CFU/cm3) applied as seed treatment and foliar application of chitosan (30 mg dm−3) on sweet pepper plants (cv. Yolo Wonder) under two salinity concentrations (34 and 68 mM). Our findings revealed that, the chlorophyll fluorescence parameter (Fv/Fm ratio), chlorophyll a and b concentrations, relative water content (RWC), and fruit yield characters were negatively affected and significantly reduced under salinity conditions. The higher concentration was more harmful. Nevertheless, electrolyte leakage, lipid peroxidation, hydrogen peroxide (H2O2), and superoxide (O2−) significantly increased in stressed plants. However, the application of B. thuringiensis and chitosan led to improved plant growth and resulted in a significant increase in RWC, chlorophyll content, chlorophyll fluorescence parameter (Fv/Fm ratio), and fruit yield. Conversely, lipid peroxidation, electrolyte leakage, O2−, and H2O2 were significantly reduced in stressed plants. Also, B. thuringiensis and chitosan application regulated the proline accumulation and enzyme activity, as well as increased the number of fruit plant−1, fruit fresh weight plant−1, and total fruit yield of sweet pepper grown under saline conditions.

Impact of chitosan on nickel bioavailability in soil, the accumulation and tolerance of nickel in Calendula tripterocarpa

Excessive heavy metals in medicinal plants cause critical health issues to humans. Therefore, in the present study, the effect of soil amendment with chitosan (0, 0.125, 0.25, 0.5, and 1%) on bioavailability and tolerance of nickel in Calendula tripterocarpa grown in a soil spiked with Ni (100 and 150 mg/kg soil) was investigated. The results showed that Ni toxicity significantly reduced plant growth and content of chlorophyll a, b but increased carotenoid levels, lipid peroxidation, and catalase (CAT) and superoxide dismutase (SOD) activities in roots and shoots. The Ni bioaccumulation was significantly higher in shoots than roots. The soil amendment with chitosan reduced Ni bioavailability in soil, as well as lowered the biological accumulation of Ni in roots and shoots, and Ni transfer to leaves. The chitosan application also increased growth parameters and levels of chlorophyll a, b and carotenoids under both normal and Ni stress conditions. Furthermore, chitosan reduced the level of malondialdehyde and the activities of SOD and CAT in roots and shoots under Ni stress. In conclusion, results indicated that chitosan through lowering bioavailability of Ni in soils can remarkably relieve adverse effects of Ni toxicity in C. tripterocarpa.

Physicochemical and Morphological Transformations of Chitosan Nanoparticles across the Gastrointestinal Tract and Cellular Toxicity in an In Vitro Model of the Small Intestinal Epithelium

Nanoscale chitosan materials exhibit size-specific properties that make them useful in agri-food and biomedical applications. Chitosan nanoparticles (Chnps) are being explored as nanocarrier platforms to increase oral bioavailability of drugs and nutraceuticals, but little is known of their fate and transformations in the gastrointestinal tract (GIT) or of their potential toxicity. Here, the GIT fate and cytotoxicity of Chnps, soluble starch-coated Chnps (SS-Chnps), and bulk chitosan powder (Chp), were assessed using a 3-phase simulated digestion and an in vitro cellular small intestinal epithelium model. Physico-chemical characterization revealed dissolution of Chp, but not of Chnps or SS-Chnps, during the gastric phase of digestion, stability of the starch coating of SS-Chnps in the oral and gastric phases, and agglomeration of all materials during the small intestinal phase. A slight but significant (10%, p < 0.01) increase in cytotoxicity (LDH release) was observed with exposure to digested Chnps but not Chp or SS-Chnps.

Carbohydrate polymers exhibit great potential as effective elicitors in organic agriculture: A review

Some carbohydrate polymers, usually oligosaccharides or polysaccharides, have great potential as an elicitor of plant defense. However, due to the complexity and diversity of poly- and oligosaccharide structure, the molecular mechanisms and structure-activity relationships of carbohydrate elicitors are still not well understood, which hinders the application of carbohydrate elicitors in agriculture. This review introduces the mechanisms of carbohydrate elicitor perception and signaling in plants. The structure and activity relationships of main poly- and oligosaccharides studied for the control of plant diseases are discussed and summarized. Additionally, the effects of carbohydrate elicitors on the secondary metabolite production are also summarized.