It is generally accepted that tomato plants require lots of direct sunlight in order to grow to their full potential. This is both true and untrue depending on the variety, growth habit and age.
A variety such as Tumbling Tom in full sunshine for most of the day will struggle to absorb enough water through its roots to replace the moisture evaporating through its many leaves when it is in hot, direct sunshine.
A variety such as Red Alert, which has less leaves, will need less water to supply to its leaves and therefore cope better in hot sunshine. It is also the case that a plant with a well developed root system will cope better in all conditions and produce a better crop.
Varieties that originate in Southern Europe, such as Italian and Spanish varieties, will do better in hot weather than those that come from cooler areas of the world.
I'm writing about this subject because, in the UK, we are in the middle of some very sunny and warm weather and some of my tomato plants are wilting in the hot sun!
When this happens I'll move them into the shade and give their leaves a spray misting with water ... twenty minutes later they'll look a lot happier.
It is also true about tomato plants that some varieties need to be acclimatised to direct sunlight. No ... this is not April the 1st ... it's just that tomato plants have huge divergences in growth habit and requirements which make growing tomatoes all the more interesting and rewarding.