Transcription activator that binds to the DNA consensus sequence 5'-[ACG]CGCG[GTC]-3' (By similarity). Regulates transcriptional activity in response to calcium signals (Probable). Binds calmodulin in a calcium-dependent manner (By similarity). Involved in freezing tolerance in association with CAMTA1 and CAMTA3. Contributes together with CAMTA1 and CAMTA3 to the positive regulation of the cold-induced expression of DREB1A/CBF3, DREB1B/CBF1 and DREB1C/CBF2 (PubMed:23581962). Involved together with CAMTA3 and CAMTA4 in the positive regulation of a general stress response (PubMed:25039701). Involved in tolerance to aluminum. Binds to the promoter of ALMT1 transporter and contributes to the positive regulation of aluminum-induced expression of ALMT1 (PubMed:25627216). Expressed in roots, stems, old leaves, petals, sepals, top of carpels, stigmas, stamen filaments, anthers and siliques, but not in pollen. By salt, wounding, abscisic acid, H(2)O(2) and salicylic acid (PubMed:12218065). Induced by aluminum (PubMed:25627216). No visible phenotype under normal growth conditions, but the double mutants camt2 and camt3 exhibit dwarf phenotypes. Belongs to the CAMTA family.