Effect of ABA on C. reinhardtii in dense cultures
C. reinhardtii cells were harvested by centrifugation at 1500 g for 10 min and then inoculated onto 50 ml of fresh Tris-minimal medium (Gorman and Levine, 1965) to an OD750 of 1. For ABA experiments, stock of ABA solution was prepared by dissolving ABA powder (Duchefa Biochemie) in HPLC-grade ethanol to a final concentration of 100 mM. The stock solution was very concentrated to minimize the added volume to the algal cultures. To investigate the effect of ABA on the growth of C. reinhardtii under salt stress, two different concentrations of ABA were checked. Cultures were treated with 0 (control), 500 µM ethanol (mock), 50 and 500 µM ABA, and NaCl was added to the cultures to a final concentration of 125 mM (this concentration was chosen based on the results of the previous section). The cultures were then further incubated for 48 h under continuous illumination of 100 μmol photons m−2 s−1 for 48 h without dark periods.