Overview of the experimental set-up. Using a system for synchronized floral induction (pAP1:AP1:GR ap1 cal), different developmental stages were analyzed: meristem specification (stage 2; 2 days after induction), organ specification (stage 4-5; 4 days after induction), and organ differentiation (stage 7-8; 8 days after induction). Around day 4, organ identity genes specify the floral whorls within the meristem, and sepal growth has been initiated. At day 8, sepals are largely differentiated, and the organs in the inner whorls are being formed. The experimental techniques used at each time point are indicated in the lower part of the figure. For illustrative purposes, images of wild-type floral meristems of the respective stages (color) are indicated above the graph.