The study investigates the role of auxin in the initiation and radial positioning of plant lateral organs, specifically leaves and flowers. The authors use tomato shoot apices and Arabidopsis pin-formed1-1 (pin1-1) inflorescence apices to demonstrate that auxin is essential for organogenesis and plays a crucial role in determining the radial position of lateral organs. Inhibition of polar auxin transport with NPA blocks leaf formation in tomato apices, leading to pinlike structures devoid of leaves. Local application of indole-3-acetic acid (IAA) to these pinlike structures restores leaf formation, indicating that auxin is both necessary and sufficient for organ induction. Similarly, IAA treatment on the flanks of Arabidopsis pin1-1 inflorescence apices induces flower primordia, suggesting that auxin triggers organogenesis without determining organ identity. The study also shows that the radial position of organ initiation is strictly correlated with the site of IAA application, while the apical-basal position is determined by a fixed distance from the meristem summit. These findings suggest that auxin determines the radial position and size of lateral organs, while other factors in the meristem determine organ identity and apical-basal position. The authors propose a model where auxin-mediated radial patterning is superimposed on the basic apical-basal pattern in the meristem, with preexisting leaves influencing the radial position through their vasculature.The study investigates the role of auxin in the initiation and radial positioning of plant lateral organs, specifically leaves and flowers. The authors use tomato shoot apices and Arabidopsis pin-formed1-1 (pin1-1) inflorescence apices to demonstrate that auxin is essential for organogenesis and plays a crucial role in determining the radial position of lateral organs. Inhibition of polar auxin transport with NPA blocks leaf formation in tomato apices, leading to pinlike structures devoid of leaves. Local application of indole-3-acetic acid (IAA) to these pinlike structures restores leaf formation, indicating that auxin is both necessary and sufficient for organ induction. Similarly, IAA treatment on the flanks of Arabidopsis pin1-1 inflorescence apices induces flower primordia, suggesting that auxin triggers organogenesis without determining organ identity. The study also shows that the radial position of organ initiation is strictly correlated with the site of IAA application, while the apical-basal position is determined by a fixed distance from the meristem summit. These findings suggest that auxin determines the radial position and size of lateral organs, while other factors in the meristem determine organ identity and apical-basal position. The authors propose a model where auxin-mediated radial patterning is superimposed on the basic apical-basal pattern in the meristem, with preexisting leaves influencing the radial position through their vasculature.