Chitosan is a novel biopolymer that acts as a biostimulant and has become promising material due to its low cost, biocompatibility, biodegradability, and excellent alternative to other materials due to its physicochemical characteristics, chemical stability, high reactivity, excellent chelation behavior with heavy metals, and high selectivity toward pollutants.
Chitosan can induce the defense system in both pre and post harvest fruits and vegetables and helps fight fungi, viruses, bacteria and any other abiotic stresses. Moreover Chitosan effectually boosts the physiological properties of plants and also raises the shelf life of post harvest produces.
Chitosan is produced from the exoskeleton of shellfish such as prawns, crabs, and lobsters. Chitosan is obtained from the deacetylation of chitin.
Chitin is an abundant natural polysaccharide produced by arthropods and crustaceans such as crabs, and shrimp and in the exoskeleton of marine zooplankton that also has chitin in their wings. Both marine and freshwater invertebrates are good sources of chitin and chitosan.. Chitin is found in diatoms, nematodes, and mollusks as a structural polysaccharide constituting almost 16% of the dry weight of the organism. Chitin is one of the most bounteously available polymers after cellulose.
The commonly used production procedure consists of two main step:
- Demineralisation
- Deproteinisation
APPLICATIONS OF CHITIN AND CHITOSAN
Chitosan and its derivatives have practical applications in the food industry, agriculture, horticulture, pharmacy, medicine, cosmetology, textile and paper industries, wastewater treatment, and chemistry.
CHITOSAN IN HORTICULTURE
Chitosan-based materials exhibit various exciting properties, which make them applicable in many fields, including agriculture and horticulture, where they are used as biostimulants. Chitosan induces several defensive genes in plants, such as pathogenesis-related genes, like glucanase and chitinase. It also induces many enzymes in the reactive oxygen species scavenging system, such as superoxide dismutase, catalase, and peroxidase. The signal transduction pathway from chitosan that elicits its responses involves hydrogen peroxide and nitric oxide signals, and it may also directly control gene expression by interacting with chromatin. Chitosan has been used both as a biostimulant to stimulate plant growth and abiotic stress tolerance, and to induce pathogen resistance; however, these responses are complex and they depend on different chitosan-based structures and concentrations as well as the plant species and developmental stage.
How exactly does chitosan help plants:
Chitosan functions as a plant growth promoter in various crops such as beans, potatoes, radishes, gerbera, soybean, cabbage, and other crops. As a result of plant growth promotion, it also enhances yield. Chitosan greatly influences the growth rates of shoots, roots, flowering, and the number of flowers. As chitosan molecules are extremely hydrophilic, they reduce stress damage in plant cells by decreasing water content and accelerating several biological macromolecules’ activities.
Some of the several applications are summarized below:
a. Seed germination:
Seed priming with chitosan makes seedlings more resistant to abiotic stress.
b. Plant resistance ability:
Their potent effect on plant disease control is from their antimicrobial and plant innate immunity-elicited activity. The inhibition activity was observed on different stages of fungal growth such as mycelia, sporulation, spore viability and germination, and production of fungal virulence factors
- increase photosynthesis,
- decrease transpiration rates
- increase frost tolerance
- increase turgidity(less lodging)
- strong efficiency agent for fungal bacterial viral infections
c. Chitosan influence on abiotic stress:
application of chitosan in plants has been less diverse, especially under abiotic stresses. As far as drought is concerned, chitosan induces numerous beneficial responses in plants such as antitranspirant, activation of ROS scavenging system, enhanced stomatal conductance, improved root growth, and overall plant development. It is non-toxic and environmental friendly which will gain much value in the use of sustainable agricultural practice.
In conclusion, the effective use of chitosan plays a key role in horticulture crops due to their bioactivities as antifungal activity, enhancement of crop yield, induction of defensive system of plants, and plant growth promotion. However, In spite of its unique biological aspects, the water-insoluble property is another major limiting factor for its wide application in horticulture. Recently, to overcome these problems, chitosan derivatives and oligomers produced by enzymatic and chemical modifications have been proposed. It is expected that these modified biopolymers would be promising candidates in agriculture. Research is also in progress on the mechanisms of chitosan-induced defense and on the signal perception of chitosan. Thus chitosan can be centered upon for its multiple roles in horticultural crop betterment that could be useful in future crop enhancement programs.
