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. Also active on other carotenoid substrates like licopene or zeaxanthin. 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 flowers, siliques, inflorescence stems, petiole and leaves, and at a much higher level in roots. Up-regulated by auxin in the root and hypocotyl. Increased shoot branching. The branching phenotypes of the max1, ccd7/max3 and ccd8/max4 mutants can be rescued by exogenous treatment with the synthetic strigolactone analogs GR24 and 4BD. Belongs to the carotenoid oxygenase family.