I don't think that would really matter . . .
Just as we would expect ET to be vastly different from the basic humanoid form, the same must be true of plantlife. Even if the plant's "blood", we'll say, is similar to the Earth's chlorophyll, it would have evolved over millions, possibly billions of years to the influence of its prime feeder, the star around which the planet would revolve. Plants might not even have an oxygen output, but sulfur.
Until we actually get there, whose to say? Physics is physics, but chemestry gets weird.