Salt's Function in Bread
Salt's main function is to bring out the flavor of the baked product. Salt tends to bring out the good flavors and mask the off-flavors.
2. Inhibits Fermentation
Salt will actually dry up the yeast cells much like the sun will dry up a grape and turn it into a raisin. When you are adding your salt to your bowl, it's best not to add it directly on top of the yeast you just added. Since salt slows down the fermentation it can be can be used to control the fermentation rate of sponges or sourdough breads. Slowing down fermentation rate means that less sugars are metabolized by the yeast into acids. The result is that the pH of the dough will be higher and the crust color will be darker.
3. Salt Toughens the Gluten
The fact that salt toughens the gluten, could be helpful when using a flour with less gluten like Spelt compared to Hard Red flour. Since it strengthens the gluten it also lengthens the mixing time when making bread. It's common to delay the addition of the salt to the mixer until the end of the mix especially if you are kneading the dough by hand.
4. No Salt Creates A light Colored Crust
Lastly, bread with no salt will have a crust which is lighter in color (given the same baking time and oven temperature). This can be explained as follows. Salt will slow down fermentation, so when there is no salt, the yeast activity will increase i.e. the yeast will metabolize more sugar in a given period of time. As a result there will be less sugars left in the dough and the pH of the dough will be lower (more acids will be formed). Sugars play (together with proteins, moisture and heat) an important role in the Maillard reaction. But the Maillard reaction is also influenced by the pH : a higher pH will speed up the Maillard reaction. So in this case where the pH is lower and where there are less sugars left, the color of the crust is lighter.