ASHS 2025 Conference

Basil (Ocimum basilicum) is a widely cultivated culinary and medicinal herb valued for its aroma, flavor, and nutraceutical properties. During hydroponic greenhouse production, precise regulation of air and nutrient solution temperatures plays a crucial role in enhancing yield and nutritional quality. Basil's inherent sensitivity to temperature makes it crucial to optimize these factors, as they have a significant impact on its bioactive metabolite profile. This study aimed to determine the impact of air and nutrient solution temperature on bioactive metabolites in hydroponically grown sweet basil to maximize accumulation. In a greenhouse sweet basil ‘Nufar’ were propagated in ebb-and-flow hydroponic systems for two weeks then transplanted into deep-water culture hydroponic systems and grown for three weeks. Air temperatures ranged from 20 to 30°C with a 5°C difference in day and night temperature and deep-water culture nutrient solution temperatures ranged from 15 to 35°C. At harvest, total phenolics (TPs), total flavonoids (TFs), and antioxidant activity including ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)), FRAP (ferric reducing antioxidant power), and DPPH (2,2-Diphenyl-1-picrylhydrazyl) were measured. Air and nutrient solution temperature interacted to influence all parameters measured, with nutrient solution temperature exerting a greater influence on metabolite accumulation and antioxidant activity than air temperature. As air temperature increased from 20.3 to 28.5°C, TPs and TFs decreased by 40% and 58%, respectively, while ABTS, DPPH, and FRAP antioxidant activity decreased by 18%, 67%, and 53%, respectively. Similarly, increasing the nutrient solution temperature from 14.6 to 24.9°C resulted in a 76%, 87%, and 84% decline in TPs, TFs, and FRAP antioxidant activity, respectively. A greater increase in nutrient solution temperature from 14.6 to 30.0 and 32.3°C led to a 95% reduction in DPPH and 57% reduction in ABTS antioxidant activity, respectively. Thus, if enhancing phenolics, flavonoids, and antioxidant activity of sweet basil ‘Nufar’ is a primary production goal, maintaining an air temperature of ~23°C and a low nutrient solution temperature of ~14°C is an effective strategy.