Transcription factor that acts as a repressor of reproductive development, meristem size and plant growth (PubMed:27402171). Regulates meristem size, cell size and cell number during plant development (PubMed:27660483). Binds to the promoters of the cell cycle regulators CYCB1-2 and SMR4, and genes involved in cell wall organization, such as XTH9, EXPA1 and EXPA3 (PubMed:27660483). Possesses transactivation activity in yeast (PubMed:25093810). Possesses transactivation activity in plant protoplasts (PubMed:27660483). Plays a role in abiotic stress response by binding to the 5'-CAGCTG-3' DNA sequence found in the promoters of MYB44 and TRX8 (PubMed:27660483). Plays a role in osmosensory response by binding to the 5'-AGCTGT/G-3' DNA sequence found in the promoters of the hypoosmolarity-responsive genes CYP707A1 and CYP707A3 (PubMed:25093810, PubMed:27660483). Binds to the 5'-AGCTGT-3' DNA sequence found in the promoter of the ZAT1 gene in response to abiotic stresses, such as oxidative stress, high-light, osmotic shock, salt and heat stresses (PubMed:26923089). Forms homodimers. Transiently accumulates in the nucleus when cells are exposed to hypoosmotic conditions. Expressed in roots, leaves and flowers (PubMed:25093810). Expressed in the root tips, lateral root primordia, and guard cells of leaves, hypocotyls and anthers (PubMed:27660483). Increased size of rosette leaves, increased plant height and increased length of siliques. Plants lines expressing a bZIP29-SRDX dominant-negative repressor under a constitutive 35S promoter are seedling lethal.