The acids in the dressing and the oxidation are what cause the wilting.
        
             
        
        
        
Enzymes are highly specific proteins that function best at certain pHs. A change in pH would affect its structure; too high or too low would cause denaturation. When this happens, the enzyme won’t have the correct structure to function as a catalyst. Therefore, reaction rate will slow. 
Hope this helps!!
        
             
        
        
        
The random movement of molecules across a concentration gradient until the difference in concentration between two regions is near zero.
Im thinking it's active transport :) hope it helps.