There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Chitosan (CHT) is a natural, safe, and cheap product of chitin deacetylation, widely used by several industries because of its interesting features. The availability of industrial quantities of CHT in the late 1980s enabled it to be tested in agriculture. CHT has been proven to stimulate plant growth, to protect the safety of edible products, and to induce abiotic and biotic stress tolerance in various horticultural commodities. The stimulating effect of different enzyme activities to detoxify reactive oxygen species suggests the involvement of hydrogen peroxide and nitric oxide in CHT signaling. CHT could also interact with chromatin and directly affect gene expression. Recent innovative uses of CHT include synthesis of CHT nanoparticles as a valuable delivery system for fertilizers, herbicides, pesticides, and micronutrients for crop growth promotion by a balanced and sustained nutrition. In addition, CHT nanoparticles can safely deliver genetic material for plant transformation. This review presents an overview on the status of the use of CHT in plant systems. Attention was given to the research that suggested the use of CHT for sustainable crop productivity.

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Chitosan Effects on Plant Systems

In agriculture, current control of pathogens relies mainly on chemical fertilizers and pesticides. However, alternative solutions are needed due to concerns for public health, environmental protection, and development of resistant pests. Chitosan is a nontoxic, biodegradable biopolymer showing antimicrobial and plant-immunity eliciting properties. Here, we review chitosan antimicrobial activities, modes of action, and the elicitation of plant defense responses. The major points are the following: (1) Chitosan exhibits various inhibitory efficiency against bacteria, fungi, and viruses; (2) the five main modes of action of chitosan are electrostatic interactions, plasma membrane damage mechanism, chitosan-DNA/RNA interactions, metal chelation capacity of chitosan, and deposition onto the microbial surface; (3) the elicitation of plant defense responses by chitosan may be related to various pathogenesis-related proteins, defense-related enzymes, and secondary metabolites accumulation, as well as the complex signal transduction network. The facing problems and strategies for antimicrobial mechanism research and agricultural application of chitosan are also discussed.

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Chitosan antimicrobial and eliciting properties for pest control in agriculture: a review

Engineered chitosan based nanomaterials: Bioactivities, mechanisms and perspectives in plant protection and growth.

Recent progress in the structural modification of chitosan for applications in diversified biomedical fields

Antimicrobial and inhibitory enzyme activity of N-(benzyl) and quaternary N-(benzyl) chitosan derivatives on plant pathogens

Antimicrobial and antioxidant activities of hydrocarbon and oxygenated monoterpenes against some foodborne pathogens through in vitro and in silico studies.

A series of active biodegradable coatings based on chitosan, gelatin, starch, and sorbitol with or without monoterpenes (geraniol and thymol) were prepared and applied on fresh strawberry fruit as postharvest treatments. The coated fruits were inoculated with fungal spores of Botrytis cinerea and stored for 7 days at 4 °C. Decay incidence, weight loss, anthocyanins, total soluble solids (TSS), total soluble phenolics (TSP), polygalacturonase (PGase), pectin-lyase (PLase), antioxidant activity, guaiacol peroxidase (G-POD), polyphenol oxidase (PPO), and catalase (CAT) were elucidated in the fruits of experimental sets and they were compared with that of controls. The coatings showed a significant effect on the development of quality variables, with the additional effect of geraniol and thymol as a function of the polysaccharide matrix. The coatings inhibited decay incidence, reduced weight loss, delayed changes in the contents of anthocyanin, TSS, and total soluble phenolics; inhibited the increase ...

Strawberry Shelf Life, Composition, and Enzymes Activity in Response to Edible Chitosan Coatings

Twelve different samples of gel spheres were prepared from the biopolymers chitosan, alginate, and gelatin via polyion complex formation in aqueous solution with crosslinking by glutaraldehyde. Dropwise addition of a chitosan/gelatin solution into a solution containing alginate and glutaraldehyde gave the gel spheres. The effects of different ratios of glutaraldehyde (0.25%, 0.50%, 1.0%, and 2.0%), and gelatin (2.5%, 5.0%, and 10.0%) on the characteristics of the gel spheres were evaluated. An increase in the concentration of the glutaraldehyde led to forming true spheres in rigid form. By scanning electron microscopy (SEM), the gel spheres showed fibrous network propagation along the gel membrane surface. Fourier transform infrared (FT-IR) spectroscopy confirmed the crosslinking of the amino groups by the glutaraldehyde and the presence of crosslinking bonds between the amino groups of chitosan and the carboxyl groups in the alginate molecule. Swelling studies showed that increasing the degree of...

Preparation and Characterization of Biopolymers Chitosan/Alginate/Gelatin Gel Spheres Crosslinked by Glutaraldehyde

This study focuses on the biological activities of eleven chitosan products with a viscosity-average molecular weight ranging from 22 to 846 kDa in combination with the most active monoterpenes (geraniol and thymol), out of 10 tested, against four plant pathogenic bacteria, Agrobacterium tumefaciens, Erwinia carotovora, Corynebacterium fascians, and Pseudomonas solanacearum. The antibacterial activity was evaluated in vitro by the agar dilution technique as a minimum inhibitory concentration (MIC) that was found to be dependent on the type of the microorganism tested. The most active product of chitosan was used for biofilm production enriched with geraniol and thymol (0.1 and 0.5%) and the films were also evaluated against the tested bacteria. The biological bioactivities summarized here may provide novel insights into the functions of chitosan and some monoterpenes and potentially allow their use for food protection from microbial attack.

https://downloads.hindawi.com/journals/scientifica/2016/1796256.pdf

Nehad E. M. Taktak

Papers

Antimicrobial and inhibitory enzyme activity of N-(benzyl) and quaternary N-(benzyl) chitosan derivatives on plant pathogens

Antimicrobial and antioxidant activities of hydrocarbon and oxygenated monoterpenes against some foodborne pathogens through in vitro and in silico studies.

Strawberry Shelf Life, Composition, and Enzymes Activity in Response to Edible Chitosan Coatings

Preparation and Characterization of Biopolymers Chitosan/Alginate/Gelatin Gel Spheres Crosslinked by Glutaraldehyde

The Antibacterial Activity of Chitosan Products Blended with Monoterpenes and Their Biofilms against Plant Pathogenic Bacteria