Oligosaccharides derived through irradiation of polysaccharides act as efficient plant elicitors and stimulate responses associated with primary as well as secondary metabolic pathways in plants. Reduced molecular weight together with the structural rearrangement, induce plant growth promotion activity in the polysaccharides after irradiation. In addition to the increased activities of different enzymes involved in photosynthesis and nutrient assimilation, various secondary metabolism enzymes are up-regulated by the leaf-applied oligomers. Oligosaccharide-induced elicitation of different signal transduction cascades leads to the increased biosynthesis of valuable secondary metabolism products in plants. The present review presents a comprehensive approach regarding the irradiation-induced structural changes and molecular weight reduction in polysaccharides and their role in increasing the production of economically valuable secondary products in various medicinally important plants. This review also encompasses the role of oligosaccharides in regulation of plant growth and enzyme activities as well as the signal transduction mechanism involved in the elicitation of secondary metabolites.
Keywords: Alkaloids; Oligosaccharides; Secondary metabolites; Tryptophan carboxylase.
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