Catalyzes the 16alpha,17-epoxidation on non-13-hydroxylated gibberellins (GAs), including GA4, GA9, and GA12. No activity with GA1, GA20, GA53 or ent-kaurenoic acid. Reduces the biological activity of GAs. Expressed in rapidly elongating or dividing tissues, including the shoot apical meristem, the intercalary meristem and elongating zones of internodes, and panicle but not in young seedlings, roots and leaves. During the heading stage, the highest expression is detected in the flowering spikelets, anthers, the divisional zone and the node of the uppermost internode. Overexpression of CYP714D1 causes severe dwarfism and sterility. Belongs to the cytochrome P450 family.