The present invention provides polynucleotides and related polypeptides (SEQ ID NO: 1 and 2) of the ZmARGOS (Auxin-Regulated Gene involved in Organ Size) gene family. The invention provides genomic sequence for the ZmARGOS genes. ZmARGOS is responsible for controlling plant growth, organ size and yield in crop plants. Transgenic plants expressing ZmARGOS show a positive impact on biomass accumulation and rate of maize plant growth, as well as an increase in organ size. These maize genes will find utility for enhancing agronomic traits in maize (and other crops).