>Roots in PIE that alternate a/nothing ..
>Roots in PIE that alternate a/o ..
There's two kinds of alternation here. There's a big difference between
(a) Alternation One:
Roots which show /a/ in some languages, and zero (or /o/) in others.
(b) Alternation Two:
Roots which show /a/ and zero (or /o/) in the same language.
If we are comparing /a/ alternations with the ablaut vowel /e~o~zero/, then
it is the second kind we need, not the first. So where are your examples?
Peter