The Atss3 mutant and WT plants were arranged according to a Randomized Complete Block Design. The plants were planted in rows with seven rows in each flat; two plants of the same genotype/pot. Plants were grown under a SD photoperiod (8 h light/16 h dark) in a growth chamber as described. Eight randomly selected rows were harvested for each time point from different flats. Plant material was harvested at five time points in the diurnal cycle (1, 4, 8.5, 12, and 16 h; Time 0 is the beginning of the light period); harvesting was conducted under a green safety light. Each sample consisted of rosette leaves (leaves 5 to 8, staged following Bowmann (1994); photosynthetically active (Stessman et al., 2002)) from sixteen six-week-old plants. Leaf samples were frozen in liquid N2 immediately after harvest and stored at -80C for RNA extraction. The experiment was done twice and independent randomizations for plant growth and harvest were used for the two replicates.