Has a 11,12(11',12') 9-cis epoxycarotenoid cleavage activity. Catalyzes the first step of abscisic-acid biosynthesis from carotenoids. Not active on the all-trans isomers of violaxanthin and neoxanthin. Contributes probably to abscisic acid synthesis for the induction of seed dormancy. 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. Vmax with 9-cis violaxanthin as substrate is more than twice the Vmax with 9-cis neoxanthin as substrate. Partially bound to the thylakoid membranes. Expressed in leaves, roots and embryos. By drought stress. The N-terminal amphipathic alpha-helix (81-100) is essential, but not sufficient, for the thylakoid membrane targeting. Plants show a viviparous phenotype. Belongs to the carotenoid oxygenase family.