I should note as a follow up to yesterday’s post that the Rosh rejects the opinion that allows women to say a bracha on a zman gerama mitzvah precisely because the wording of “v’tzivanu” does not apply to them.
Tosfos (R”H 33) discusses whether one can bring proof to the position that women may say brachos on mitzvos she’hazman gerama from the fact that a woman can theoretically get an aliya (if not for the reason of kavod tzibur) and recite birchas hatorah. Since birchas hatorah recited before an aliya does not contain the term “v’tzivanu”, it would appear that more is involved in this debate than issues of language. Those who oppose women reciting the bracha may hold that Chazal simply never instituted a concept of bracha recitation for those not obligated in the mitzvah.
The Halichos Beisa quotes an interesting discussion among achronim: assuming there is no problem reciting a bracha, are women simply permitted to recite the bracha, or are they obligated to do so? In support of the later position the Halichos Beisa suggests that a birchas hamitzvah may be part and parcel of the mitzvah itself. Since women are permitted to perform mitzvos she’hazman gerama, that performance by definition includes the obligation of bracha as part of the mitzvah act. Perhaps this issue hinges on the debate in Rishonim (Rambam/Ra’avad, Milah 3:1) whether a bracha is recited when a mitzvah is performed to avoid a safeik, e.g. is a bracha recited over a milah of an andogynus.