Both Persian and Turkish - as have other "islamic" languages - have a great deal of Arabic vocabulary. Due to an (initially) favourable vowel inventory (and maybe due to the same script being used) these loans have come to Persian in much of their original shape, while their Turkish counterparts do differ quite a lot. There seems to be some regularity, but I did not, up to now, figure it out completely. So the question is: how do (especially vowel) sounds change, when a word travels from Arabic to Turkish? How about the same thing for Persian words in Turkish? To understand these processes better: what was the general way of Arabic words coming to Turkish, I mean by way of which idiom or even language did Arabic words come to modern Turkey-turkish?
Now what I figured out up to now is this:
The short vowels a, i and u in Arabic can be realized in Turkish as a/e, i/ı and u/ü respectively. This accords with the vowel harmony and it seems, that there is some connection with a kind of "consonant harmony" which is familiar to me from Old Uyghur, to the effect that the dark vowel is chosen in circumstances of dark consonants like q, 'ayn and the retroflex l. And of course vice versa, the light vowel being used in appropriate consonant surroundings.
Does anybody know more about that, since it does not seem to be the be-all and end-all?