Effect of Ascophyllum extract on cell division, proximate composition, antioxidant response and internal plant hormone composition in green seaweed Ulva ohnoi (Chlorophyta)

Genus Ulva is commercially exploited for diverse potential, emerging and established applications ranging from food, animal feed, aqua feed, plant bio-stimulant, bioenergy, and biomedical applications of its polysaccharide. This study aims to investigate the effects of Ascophyllum Marine Plant Extract Powder (AMPEP) at different concentrations (0.01, 0.05, 0.1 and 0.5 %) and times (15, 30, and 60 min) on the growth, physiology, and biochemical composition of the green seaweed Ulva ohnoi. Treatment with 0.5% AMPEP for 30 minutes significantly increased ratio of divided and undivided cells on day-4 (6.43 ± 2.36). Additionally, a 1.2-fold enhancement in gross primary productivity (GPP), chlorophyll-a, -b, and total chlorophyll content indicated an overall improvement in photosynthetic efficiency. The levels of carotenoids and auxins showed 2.1 and 6.4-fold increases, respectively. Similarly, a 1.4 and 1.2-fold rise in total carbohydrate content and antioxidant capacity was observed. Moreover, antioxidant enzymes, catalase (CAT), glutathione reductase (GR), and superoxide dismutase (SOD) were significantly elevated in the AMPEP-treated thallus, underscoring the improved stress tolerance and metabolic vigour of the treated plants. To the best of our knowledge, this is the first-ever study on the effect of AMPEP on green seaweed Ulva. This bio-stimulatory effect would undoubtedly be helpful in enhancing the growth and yield of Ulva in tank and multi-tubular airlift photobioreactor-based cultivation protocol.