Why China Embassy in Italy doesn't issue visas to Iranians students

I'm a PhD student at Italy (but Iranian citizen) and I have been invited to to present
an accepted paper at International conference which held at Guangzhou of China.
I want to apply for visa of China but since I haven't a long term permit of stay in Italy
( 5 years valid or unlimited ) I will not be allowed to apply from Italy.

Would you please let me know if there is any solution in my case or
if my representative in Iran can apply behalf of me?