Catalysis of the reaction: a (9Z)-octadecenoyl-containing glycerolipid + 2 Fe(II)- + 2 H+ + O2 = a (9Z,12Z)-octadecadienoyl-containing glycerolipid + 2 Fe(III)- + 2 H2O.
1-16:0-2-18:1-phosphatidylcholine desaturase activity