Employing radiation-processed carrageenan, sodium alginate, and chitosan improves physiological characteristics and production of essential oil and citral content in Cymbopogon flexuosus under heat stress

Extreme temperatures can stunt plant growth, lowering crop productivity. Radiation-processed natural polysaccharides like carrageenan, sodium alginate, and chitosan trigger plant defense mechanisms to reduce stress from drought, salinity, and high temperatures. This study examined the stress-relieving effects of foliar gamma-irradiated natural polysaccharides (ICA, ISA, and ICH) at 80, 60, and 80 mg L-1 on lemongrass grown at 30°C (Control), 40°C, and 45°C. This study demonstrated that high temperature stress (40°C and 45°C) severely influences lemongrass development, essential oil yield, and its active constituents. The greatest loss was 17.23% in plant height and 34.60% in dry weight at 45°C. At 45°C, essential oil yield and total citral content% decline by 32.37% and 11.73%, respectively, from the control group. ICA, ISA, and ICH foliar-spray treatments minimized high-temperature stress by enhancing plants’ antioxidant defense system, improving all metrics compared to 40°C, 45°C, and water-spray control. A foliar spray of ICA, ISA, and ICH increased plant height and dry weight by (10.5%, 10.4%), (19.7%, 26.1%), and (8.1%, 9.3%) at 45°C respectively. Foliar ICA, ISA, and ICH also increased EOY by (29.7%, 54.8%, and 62.5%) and total citral content by (8.5%, 10.2%, and 10.6%) at 45°C, respectively. Thus, ICA, ISA, and ICH may alleviate lemongrass and other economically significant crop temperature stress. These biopolymers can serve as eco-friendly alternatives to synthetic agrochemicals. The molecular mechanisms controlling their signalling pathways and gene expression effects are unknown. To understand structure–function correlations and optimize irradiation techniques, future studies should combine omics and molecular modelling.