Cell diameter and palmella formation
Cell diameter was determined by means of fluorescence activated cell sorter (FACS, BD Fortessa, USA) using side scatter pulse width (SSC-W) data from cells against size calibration bead standards of polystyrene (Spherotech, USA). Briefly, six different bead standards ranging between 3 μm and 16 μm were used to plot a calibration standard curve of amplifier gains where the pulse width was independent of peak height and peak area. The curve was then fitted with a linear curve according to Sharpless and Melamed (1976), and was used to transform the median SSC-W data from a microalgal cell population of 1 × 106 cells*mL-1 into a median cell diameter (Supplementary Fig. 2).