Practice question

Hypophysis represents uppermost cell of basal lineage derived from basal cell after first highly asymmetric zygotic division; it resides at junction between suspensor file and embryo proper. It undergoes crucial asymmetric division generating lens-shaped quiescent center precursor and columella stem cell precursor, thus directly founding root meristem. Specification requires auxin flux from embryo proper via basal PIN1 polarity, MP-ARF5 mediated transcriptional response, and high auxin-induced PLT accumulation and WOX5 induction. Mutants lacking auxin perception in hypophysis exhibit horizontal division and fail to establish functional root pole.