Arabidopsis thaliana ecotypes Columbia (Col-0) and C24 were used as WT plants. Testcross experiments were conducted in gcs1/gcs1 (5 (link), 6 (link)), hap2-1/+ (9 (link)), lre/lre (15 (link)–17 (link)), and mea/mea (22 (link), 23 (link)) and in WT plants. The RPS5Apro::tdTomato-LTI6b (11 (link)) and CycB1;2pro:CycB1;2::NLS-YFP (12 (link)) lines were used for POEM assays. Seeds were sterilized with 5% sodium hypochlorite containing 0.5% Triton X-100 and germinated on plates containing 0.5× Murashige and Skoog salts (pH 5.7) (Wako Pure Chemical), 2% sucrose, Gamborg’s B5 vitamin solution (Sigma), and 0.3% Gelrite (Wako Pure Chemical) in a growth chamber at 21.5°C under 24 hours of light after cold treatment (4°C) for 2 days. Ten-day-old seedlings were transferred to Metro-Mix 350 soil (Sun Gro) and grown at 21.5°C under 24 hours of light.