Responsible for the deacetylation of lysine residues on the N-terminal part of the core histones (H2A, H2B, H3 and H4). Histone deacetylation gives a tag for epigenetic repression and plays an important role in transcriptional regulation, cell cycle progression and developmental events. Histone deacetylases act via the formation of large multiprotein complexes. HDA19 is involved in jasmonic acid and ethylene signaling of pathogen response. Part of a repressor complex including APETALA2 (AP2) and TOPLESS (TPL) that control the expression domains of numerous floral organ identity genes (PubMed:23034631).