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Abstract. Orabi SA, Talaat IM, Balbaa LK. 2014. Physiological and biochemical responses of thyme plants to some antioxidants. Nusantara Bioscience 6: 118-125. Two pot experiments were conducted to investigate the effect of tryptophan, nicotinamide and α-tocopherol (each at 50 and 100 mg/L) on plant growth, essential oil yield, and its main constituents. All treatments significantly promoted plant height, and increased fresh and dry mass (g/plant) of thyme (Thymus vulgaris L.). The treatment with 100 mg/L nicotinamide showed increases in total potassium mainly in the first cut. Total soluble sugars, oil percentage, and oil yield and protein recorded increments with tryptophan treatments. Treatment of Thymus plants with 100 mg/L nicotinamide observed the highest percentage of thymol (67.61%). Oxygenated compounds recorded the highest value with 50 mg/L α-tocopherol treatment, while the maximum non-oxygenated ones resulted from the application of 100 mg/L nicotinamide. All treatments under study significantly affected the activity of oxidoreductase enzymes (POX and PPO). Nicotinamide at the concentration of 100 mg/L recorded the highest increments in APX and GR and the lowest values in oxidoreductase enzyme activities added to the lowest values of lipid peroxidation to enhance the best protection of thyme plants.

Abstract. Orabi SA, Talaat IM, Balbaa LK, Abdalla AE. 2015. Influence of pyridoxine and spermine on lemongrass (Cymbopogon citratus) plants. . Two pot experiments were conducted to investigate the effect of pyridoxine and spermine (each at 50, 100 and 200 mg/L) on plant growth, essential oil yield and its main constituents. All treatments significantly promoted plant height, fresh and dry mass (g/plant) of Cymbopogon citratus L., especially 100 mg/L spermine which mostly recorded the highest increments in total nitrogen, total phosphorous and total potassium mainly in the second cut, followed by 200 mg/L pyridoxine. Total phenols, essential oil % and oil yield recorded the maximum increments with spermine treatments followed by pyridoxine. Treatment of lemongrass plants with 100 mg/L spermine gave the highest relative percentage of citronellol (51.20%). Oxygenated compounds recorded the highest value (89.70%) with 200 mg/L spermine treatment, while the maximum non-oxygenated ones resulted from the untreated plants (13.65%). All treatments under study significantly affected the scavenging ability of the natural antioxidants of the plant extract towards the stable free radical DPPH (2, 2-diphenyl-1-picryl-hydrazyl-hydrate). Application of spermine at the concentration of 100 mg/L recorded the highest increment in phenylalanine ammonia lyase (PAL) enzyme activity (µg/g F.wt.).