Practice question

Heart-shaped embryo stage in Arabidopsis marks crucial transition from radial to bilateral symmetry during intermediate embryogenesis. Globular embryo with uniform cell divisions develops localized auxin maxima at apical flanks mediated by PIN1 convergence points directing periclinal divisions forming two cotyledon primordia protruding outward producing characteristic indented apex enclosing shoot meristem. Morphology indicates successful cotyledon initiation mediated by MP and NPH4 auxin response factors and boundary specification by CUC1/CUC2/STM genes, signifying onset of organogenesis and separation of functional domains in embryonic apex region essential for patterning.