In a typical angiosperm flower, the four whorls (calyx, corolla, androecium, and gynoecium) appear to arise from the same swollen base called the thalamus in a highly compacted arrangement. Which specific developmental mechanism of the shoot axis accounts for this compacted arrangement of floral appendages?

Step-by-step solution

A flower is morphologically a highly modified shoot. During floral induction, the shoot apical meristem changes to a floral meristem. For the floral appendages (which are modified leaves) to appear in a compacted arrangement on the thalamus, the internodes of the floral axis do not elongate further, causing the axis to condense. Because the internodes are condensed, the successive nodes are brought very close to each other, allowing the floral whorls to arise from what appears to be the same swollen base. Floral ap