A flower is a modified shoot because it develops from the shoot apical meristem and follows the same basic pattern of growth and differentiation as stems. The floral organs (sepals, petals, stamens, carpels) are all modified leaves that arise from the flanks of the floral meristem, just as leaves arise from the vegetative shoot meristem. This fundamental concept explains why flowers have whorled arrangements and why floral parts can sometimes revert to leaf-like structures (phyllody).