Catalyzes the 3-beta-hydroxylation of the inactive gibberellin precursors, leading to the formation of bioactive gibberellins. In vitro, converts the precursors GA20, GA5, GA44 and GA9 to the corresponding 3-beta-hydroxylated active products GA1, GA3, GA38 and GA4, respectively. Involved in the production of bioactive GA for vegetative growth and development (PubMed:11438692). Controls the elongation of the vegetative shoot and plant height by the regulation of active gibberellin levels (Ref.7). 2-oxoglutarate + gibberellin A20 + O2 = CO2 + gibberellin A1 + succinate Binds 1 Fe(2+) ion per subunit. Plant hormone biosynthesis; gibberellin biosynthesis. Highly expressed in elongating leaves. Expressed in unopened flowers. Expressed at low levels in leaf blades, shoots, rachis, stems and young panicles. During anther development, expressed in the tapetum at the early-stage and middle-stage of pollen differentiation. Induced by uniconazole. Down-regulated by gibberellin (GA3). Plants silencing G3OX2 exhibit reduced plant height. Belongs to the iron/ascorbate-dependent oxidoreductase family.