Involved in strigolactones biosynthesis by cleaving the C(27) 9-cis-10'-apo-beta-carotenal produced by CCD7. Produces the C(19) carlactone and a C(8) hydroxyaldehyde. Also shows lower activity with all-trans-10'-apo-beta-carotenal producing a C(9) dialdehyde and the C(18) 13-apo-beta-carotenone. Strigolactones are hormones that inhibit tillering and shoot branching through the MAX-dependent pathway, contribute to the regulation of shoot architectural response to phosphate-limiting conditions and function as rhizosphere signal that stimulates hyphal branching of arbuscular mycorrhizal fungi and trigger seed germination of root parasitic weeds. 9-cis-10'-apo-beta-carotenal + 2 O2 = (2E,4E,6E)-7-hydroxy-4-methylhepta-2,4,6-trienal + carlactone all-trans-10'-apo-beta-carotenal + O2 = (2E,4E,6E)-4-methylocta-2,4,6-trienedial + 13-apo-beta-carotenone Binds 1 Fe(2+) ion per subunit. Expressed in parenchyma cells of the root stele, shoot apex, leaf buds, xylem parenchyma cells of the stem, inflorescences and panicles. By auxin. Dwarf phenotype with increased branching and tiller number, and strong reduction of the root levels of strigolactones. The branching phenotypes of the ccd7/max3 and ccd8b/max4 mutants can be rescued by exogenous treatment with the synthetic strigolactone analogs GR24 and 4BD. Belongs to the carotenoid oxygenase family.