Figure 5.

Exogenous 1-naphthaleneacetic acid (NAA), 1-aminocyclopropane-1-carboxylic acid (ACC) and hydrogen peroxide (H₂O₂) did not significantly affect the vertical positioning of C. reinhardtii CC-1021 in the dark. Algal cultures were grown under a 16 h photoperiod to the mid log phase (A₇₅₀ = 0.3) growth stage and were sampled 8 h into the 16 h photoperiod. Fully dispersed algal samples were placed in measuring cylinders +/− either 50 µM (a) NAA, (b) H₂O₂ or (c) ACC, ABA and ACC + ABA to form 10 cm vertical culture columns and for 50 min were either illuminated from above with high-light (319.8 µmoles photons m⁻² s⁻¹) or placed in the dark. After incubation the A₇₅₀ at the depths indicated were measured and the relative cell density ratios for each depth were determined within each treatment. Shown are the mean data of either n = 5 (a) or n = 3 (b,c) replicate experiments +/− the 95% confidence intervals around the means in each case.