Figure 2

Exogenous abscisic acid (ABA) induced a negative geotropic movement response in C. reinhardtii CC-1021. Algal cultures were grown under a 16 h photoperiod to the mid log phase (A₇₅₀ = 0.3) growth stage and were sampled at the time points indicated over a 24 h period where the 16 h photoperiod commenced at time = 0 h. Fully dispersed algal samples were placed in measuring cylinders +/−50 µM ABA to form a 10 cm vertical water column and for 50 min were either illuminated from above with high-light (319.8 µmoles photons m⁻² s⁻¹) (A,B) or placed in the dark (C,D). Shown is a representative image of n = 5 replicate experiments indicating the positions attained by the algae immediately following the period of incubation in either the light or dark.