Converts stearoyl-ACP to oleoyl-ACP by introduction of a cis double bond between carbons 9 and 10 of the acyl chain. 2 H(+) + O2 + octadecanoyl-[ACP] + 2 reduced [2Fe-2S]-[ferredoxin] = (9Z)-octadecenoyl-[ACP] + 2 H2O + 2 oxidized [2Fe-2S]-[ferredoxin] Binds 2 Fe(2+) ions per subunit. Lipid metabolism; fatty acid metabolism. Homodimer. In green tissue, found in chloroplasts. In non-photosynthetic tissue, found in plastids. Higher levels in developing seeds than in leaf and root tissues. Belongs to the fatty acid desaturase type 2 family. Extended N-terminus.