Effects of gamma-irradiated sodium alginate on lemongrass: field trials monitoring production of essential oil

• The role of irradiated sodium alginate (ISA) as plant growth promoter for essential oil production was studied.
• ISA-60 mg L−1 significantly improved citral yield.
• Permeation chromatography study revealed formation of lower molecular weight oligomers.

Essential oil of lemongrass (Cymbopogon flexuosus (Steud.) Wats.) is the major source of the natural citral used in pharmaceutical and cosmetic industries. The role of irradiated sodium alginate (ISA) as plant growth promoter was investigated for essential oil production of this commercially important crop. Two field experiments were conducted for two consecutive years on lemongrass to study the effect of five concentrations of ISA (0, 20, 40, 60, and 80 mg L−1) in terms of plant growth and content and yield of essential oil and citral. Plant analysis was carried out at two growth stages, viz. 120 and 150 days after planting (DAP). There was a significant effect of ISA application on all the parameters including essential oil production and content and yield of citral at both growth stages. An increase of 35.85 and 23.08% was observed in ISA-60 mg L−1 over the control at 120 and 150 DAP, respectively. ISA-60 mg L−1 proved the best and enhanced essential oil yield by 103.41 and 94.86% over the control at 120 and 150 DAP, respectively. At 120 DAP, ISA-60 mg L−1 significantly improved citral yield by 181.03% over the control. Further, gel permeation chromatography (GPC) study revealed formation of lower-molecular-weight oligomers in irradiated samples, which might be responsible for plant growth promotion in the present study.

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