I have read your post three times, but, frankly speaking, did not understand what you did, why a4j:support used and what you wanted.
Thanks for your reply!
One of the selectOneMenus ought to change according to the inputText,but
all the selectOneMenus's 'get' method invoked.
Without 'a4j:support',the value of inputText can't be apply to model unless submit all form.