Figure 1.

Cytokinin increases the greening rate of etiolated Arabidopsis seedlings and alters chloroplast ultrastructure during etioplast-chloroplast transition. The wild type (WT) and ahk2 ahk3 cytokinin receptor mutants were grown for 3 d in dark on medium (MS, no Suc) before exposure to light. A, Chlorophyll content after exposure to light for 3 to 12 h. The average of three independent experiments each with three replicates per time point is shown. One replicate consisted of 30 etiolated seedlings grown on one plate. Error bars represent se (n = 3). Asterisks indicate significant differences to wild type control (* 0.05 > P > 0.01; ** 0.01 > P > 0.001; *** P < 0.001). B, Transmission electron microscope pictures illustrating the etioplast-chloroplast transition. Abbreviations: BA, 6-benzylaminopurine; (g), grana; (p), prolamellar body; (pl), prolamellar-like body; (pt), prethylakoids; (st), starch granules; (th), thylakoid membrane. Scale bars represent 1200 nm.