How to change vertical to horizontal StringArray?

How to change vertical to horizontal StringArray ?

julia> plot(rand(3,2),labels=["a", "b"])

julia> plot(rand(3,2),labels=["a" "b"])

Works fine only second line. How to change first to second vectors with lalbels ?
Paul

julia> permutedims(["a", "b"])
1×2 Array{String,2}:
 "a"  "b"