Required for plastid separation and partitioning during cell division (PubMed:22025705). Not involved in plastid constriction or in the organization of cytoplasmic actin cables (PubMed:22025705). Contributes to polar growth of root hairs (PubMed:28096376). Interacts with myosin XI-K. Localized to distinct foci in the cytoplasm, which frequently colocalize with the cell periphery and with chloroplasts. Expressed in roots, stems, leaves, apex, flowers and seeds (PubMed:20856808). Detected throughout the petiole in juvenile and young leaves, but restricted to the petiole midvein in older leaves (PubMed:22025705). Expressed in hydathodes, at the base of the trichome, in the vascular cylinder of primary root and lateral root, in emerging lateral root primordia, in pollen and in developing embryos, but not in mature embryos (PubMed:22025705). Up-regulated by heat. Normal constriction of plastids during division, but impaired separation, resulting in plastid clustering. The clumped-chloroplasts mutant phenotype is transient. In juvenile leaves, clustered chloroplasts are observed in almost all cells of the petiole, while in the oldest leaf, the phenotype is mostly absent (PubMed:22025705). Phox1, phox2, phox3 and phox4 quadruple mutants show a 70% reduction in root hair growth (PubMed:28096376).