Promotes cell proliferation-dependent organ growth. Takes part in the AXR1-dependent auxin signaling pathway that requires ANT during organogenesis. Mostly expressed in flowers, inflorescence stems, leaf primordia and young leaves, and, to a lower extent, in siliques, cotyledon vascular bundles, roots (pericycle and root tips) and mature leaves. In flowers, accumulates in stamen filaments as well as in the apices and bases of juvenile and elongating siliques. Present in leaf primordia. By auxin and ethylene (1-aminocyclopropane-1-carboxylic acid (ACC)). The OSR domain is sufficient to promote organ growth. Reduced aerial organs mainly due to changes in cell number and the duration of organ growth. When associated with ORS1 disruption, reduction in organ size. Belongs to the plant organ size related (OSR) protein family. Truncated N-terminus. Truncated N-terminus.