Exhibits GTPase activity. Component of the plastid division machinery that forms a contractile ring at the division site (PubMed:25731613). Required for plastid division in a dose-dependent manner. Involved in epidermal plastids division in a MINE1-dependent manner (PubMed:26500667). Involved in blue light-induced chloroplast movements. May regulate thylakoid development. In the vegetative shoot apex, at the shoot apical meristem (SAM), where the proplastid-to-chloroplast transition takes place, contributes equally with FTSZ2-1 in the L2 layer to plastid division (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). This aggregation is regulated in midchloroplast stroma by MIND1 (repressor) and MINE1 (promoter). Self-interacts and binds to FTSZ2-1 in heteromers to form two morphologically distinct types of filaments, termed type-I (smooth filaments) and type-II (rough filaments), in a GTP-dependent manner (PubMed:27322658). Interacts with ARC3. Part of a complex made of ARC3, ARC6, FTSZ1 and FTSZ2 (PubMed:30824505, PubMed:22823492). Forms a contractile ring at the chloroplast midpoint that coaligns with FTSZ2-1 rings (PubMed:29967285, PubMed:25731613, PubMed:26500667). Exhibits a dynamic trunover in FtsZ ring facilitated by ARC3-mediated destabilization (PubMed:25731613). In pollen grain, restricted to plastids of vegetative cells. Also present in pollen tubes plastids. Highly heterogeneous chloroplast population with giant chloroplasts and some smaller (PubMed:25731613). Impaired chloroplast division, some green cells with one single big chloroplast (PubMed:25731613). Abnormal thylakoids (PubMed:25731613). Increased plastid volume in young leaf primordia and in the shoot apical meristem (SAM), including the central zone as well as peripheral zone of L1, the outermost layer, the peripheral zone of L2, and the peripheral zone of L3 (PubMed:29920253). Belongs to the FtsZ family.