Chitosan and its oligosaccharides, a promising option for sustainable crop production- a review.

Chitosan in both native and degraded form (oligosaccharides) acts as a growth promoter and generate responses associated with both primary and secondary metabolism in plants. Chitosan and its oligosaccharides enhance photosynthesis by amplifying the activities of various enzymes of carbon and nitrogen metabolism as well as light and dark reaction of photosynthesis. They play a vital role in stimulating photosynthetic machinery by regulating primary photochemistry. They also overcome the limitations of stomata and amplify the carbon fixation efficiency in dark reactions and promote carbohydrate synthesis. Chitosan and its oligosaccharides stimulate the enzymes and content of secondary metabolites. A plausible explanation is that chitosan and its oligosaccharides acted as the suitable ligand for the induction of available receptors and thus elicit various signaling pathways viz, GPCR and PLC/PKC, MAPK, H2O2 burst, stimulation of transcription factors in the plant generating a maximum possible response. Chitosan and its oligosaccharides also exhibit antimicrobial activities and act as biopestiside, preventing proliferation of pathogens and preserve crop yield and quality.