Two EMS‑induced recessive maize mutants (o1‑2995 and o1‑tan62) were identified as novel missense alleles of opaque1 that produce O1 protein yet cause more severe morphological defects, including reduced internode elongation and altered leaf and inflorescence patterning. These alleles also partially suppress the excessive tassel and ear branching of ramosa mutants, highlighting O1’s role in regulating plant stature and architecture.