Can the salt content affect the fragrance of the dish?
If so, how does it happen?
Does salt have a fragrance of its own?
Salt itself doesn't really have a perceptible odour.
However, salt added to other ingredients will usually react with some of them, which will indeed cause a change in the dish's overall smell.
There are several different reactions involved:
- Salt will draw fluids from most fruit, vegetables and meats. The fluids have an odour that was previously trapped within the food's structure and is now available to your nose.
- Salt makes a fluid more acidic, which causes all sorts of changes. For instance, the difference in smell (and other properties) between a fresh cucumber and a pickled cucumber is mostly due to the brine, which is water with a high salt content.
- Salt may facilitate other chemical reactions in the organic molecules of the dish. Obviously, different molecules have a different smell.
Each of these reactions may occur separately or together, depending on the specific ingredients used and a host of other factors, of course, but salt can definitely cause a change in the smell of a dish.
First of a couple of assumptions:
1: Salt may react with other ingredients in ways that I can not oversee
2: Your question is purely about the way a dish smells off the plate, not indirectly when chewing.
The answer in principle is no. This topic has been discussed elsewhere on Stack Exchange, so you can read some of the theoretical background there.