Ok. I was thinking about why should plants be shaded during excessively sunny times during the day. These days over here it gets past 95F at around 11 am and remains that way until about 3 pm after which it relaxes. By that time I have lost all direct sunlight due to a tall building on the western side of my apartment and therefore at best my vegetable plants only get 3-4 hours of direct sunlight which may not be enough for my tomatoes, peppers and cucumbers.

Lets say, for example, I am somehow able to keep the temperature of the container soil down to around 90F by watering, mulching and whatever methods even if the outside temprature is above 100F. Would that still require me to shade the plant? What is the purpose of it. is it just a protective measure or is it a must to do it? And if it is a must - why?