The Effect of Abscisic Acid on the Growth Rate, Dry Biomass, Total Lipid and Photosynthetic Pigments of Nannochloropsis salina Microalgae in Guillard (F/2) Medium

Nannochloropsis salina is a promising species for lipid production, which is used in aquaculture and biofuel production. On the other hand, plant phytohormones also have different effects on the metabolism of protozoan algae. Therefore, an experiment was conducted with the aim of investigating the effect of abscisic acid (ABA) concentrations on growth and doubling time, chlorophyll, carotenoid, dry biomass, endogenous ABA and total lipid of N. salina microalgae in Gaillard (f/2) medium. The experimental treatments included 0 (control), 0.5, 10 and 20 mg L-1  ABA concentrations. This experiment was conducted in a completely randomized design (CRD) with three replications during 2019-2020. The analysis of variance showed that ABA treatment was significant on all studied characteristics at the 5% level. The treatment of 20 mg L-1 ‌‌ABA increased the growth rate, chlorophyll, endogenous ABA and total lipid in N.‌‌salina microalgae. The highest carotenoids and dry biomass were observed in 0.5 mg L-1 and control treatments, respectively. The findings of this study show that the concentration of 0.5 mg L-1 ABA is effective on lipid and carotenoid production of microalgae, but to increase total lipid production, the concentration of mg L-1 ABA is more suitable.