Gamma rays induced acquisition of structural modification in chitosan boosts photosynthetic machinery, enzymatic activities and essential oil production in citronella grass (Cymbopogon winterianus Jowitt)

Abstract Oligomers derived through irradiation of marine polysaccharides have generated a lot of interest of plant biologists as the application of these molecules has yielded positive results regarding various plant processes. To comprehend the previously established growth-promoting activity of irradiated chitosan (ICH) and to gain insight of the structure-property relationship, gamma rays induced structural changes were analyzed using techniques such as Fourier Transform Infrared (FT-IR) spectroscopy, Ultraviolet-visible (UV–Vis) spectroscopy, 13C-Nuclear Magnetic Resonance (NMR) spectroscopy and Scanning Electron Microscopy (SEM). Moreover, to study the bioactivity of ICH samples a pot experiment was conducted on citronella grass (Cymbopogon winterianus) to access its response to foliar application of various levels (40, 60, 80 and 100 mg L−1) of ICH in terms of growth, physiological attributes and essential oil (EO) production. The application of ICH at 80 mg L−1(ICH-80) resulted in the maximum values of most of the attributes studied. Due to this treatment, the maximum improvement in the content (29.58%) and yield (90.81%) of EO in Cymbopogon winterianus were achieved. Gas chromatography-mass spectrometry (GC–MS) analysis revealed that ICH-80 also increased the content of citronellal (14.81%) and geraniol (18.15%) of the EO as compared to the control.