Exhibits GTPase activity (By similarity). Component of the plastid division machinery that forms a contractile ring at the division site (PubMed:25731613). Contributes to plastid division in the vegetative shoot apex, at the shoot apical meristem (SAM) where the proplastid-to-chloroplast transition takes place (PubMed:29920253). Aggregates to form a contractile ring-like structure; contraction of the ring was accompanied by an increase in the filament turnover rate (PubMed:27322658). Self-interacts and binds to FTSZ1 in heteropolymers to form two morphologically distinct types of filaments, termed type-I (smooth filaments) and -II (rough filaments), in a GTP-dependent manner (PubMed:27322658). Part of a complex made of ARC3, ARC6, FTSZ1 and FTSZ2 (PubMed:22823492). Interacts (via C-terminus) with ARC6. Interacts with CDP1/PARC6 (PubMed:28984364). Binds to PGK1 (PubMed:22823492). Forms a contractile ring at the chloroplast midpoint (PubMed:22823492, PubMed:25731613). Exhibits a dynamic trunover in FtsZ ring facilitated by ARC3-mediated destabilization (PubMed:25731613). Phosphorylation at Thr-282 is required for the formation of contractile ring at the chloroplast midpoint. Slightly reduced number of large chloroplasts due to impaired plastid division (PubMed:25731613). Stronger effects on pastid division in the shoot apex, where the proplastid-to-chloroplast transition takes place, than in mature leaves (PubMed:29920253). Increased plastid volume in the shoot apical meristem (SAM), including the central zone as well as peripheral zone of L1, the outermost layer, and the peripheral zone of L3 (PubMed:29920253). Belongs to the FtsZ family.