Biosynthetic pathways for ABA production in higher plants and fungi. This is an abbreviated scheme showing only the major steps in the pathways. For further details consult.24,25,28 DOXP, deoxy-D-xylulose-5-phosphate; FPS, farnesyl diposphate synthase; GGPS, geranylgeranyl diphosphate synthase; PSY, phytoene synthase; PDS, phytoene desaturase; ZEP, zeaxanthin epoxidase; NSY, neoxanthin synthase; NCED, 9-cis-epoxycarotenoid dioxygenase; ABA, abscisic acid.