Has a 11,12(11',12') 9-cis epoxycarotenoid cleavage activity. Catalyzes the first step of abscisic-acid biosynthesis from carotenoids, in response to water stress. a 9-cis-epoxycarotenoid + O2 = 2-cis,4-trans-xanthoxin + a 12'-apo-carotenal 9-cis-violaxanthin + O2 = (3S,5R,6S)-5,6-epoxy-3-hydroxy-5,6-dihydro-12'-apo-beta-caroten-12'-al + 2-cis,4-trans-xanthoxin 9'-cis-neoxanthin + O2 = (3S,5R,6R)-3,5-dihydroxy-6,7-didehydro-5,6-dihydro-12'-apo-beta-caroten-12'-al + 2-cis,4-trans-xanthoxin Binds 1 Fe(2+) ion per subunit. Inhibited by abamine and abamineSG. Plant hormone biosynthesis; abscisate biosynthesis. Partially bound to the thylakoid. Localized in roots, leaves, stems, empty silique envelopes and seeds. Expressed at the point of organ attachment and the abscission zones in the plant. By salt or drought stress and pathogen. Plants show enhanced germination on salt and hypersensitivity to desiccation and LiCl. Overexpression of NCED3 results in increased accumulation of abscisic acid and resistance to water stress. Belongs to the carotenoid oxygenase family.