Figure 1. Cell size affects OD₇₅₀ measurements.

(a) Cells of Chlorella vulgaris grown photoautotrophically in unsupplemented TP have a smaller average diameter than (b) cells grown to stationary phase in Tris-Phosphate (TP) medium containing 100 mM glucose. (c) Changes in cell morphology affect the relationship between OD₇₅₀ and biomass dry weight, yielding different calibration factors (line slope) for C. vulgaris in TP (○) and in TP + 100 mM glucose (•). Error bars are standard error of the mean (SEM; n = 3).