I do not claim to be a expert or anything so take my opinion with a grain of salt! I am not trying to start another defoliation argument either since there are plenty of those threads!!
I do a ton of reading on the subject. I have read Teaming with Microbes along with a few Botany books. I am now building no till buckets so I can see for myself how it works.
Every leaf on the plant is important to the growth and health of the plant. Without leafs the plant will suffer!
Here is a quote:
"Plants make food in their leaves. The leaves contain a pigment called chlorophyll, which colors the leaves green. Chlorophyll can make food the plant can use from carbon dioxide, water, nutrients, and energy from sunlight. This process is called photosynthesis."
From here:
http://www.mbgnet.net/bioplants/food.html
"efficient photosynthesis and the formation of complete carbohydrates is the foundation of plant health and immunity. Without efficient photosynthesis, plants will not achieve any level of immunity or performance. With functional photosynthesis and adequate levels of minerals and trace minerals to serve as enzyme cofactors, formation of complete proteins is initiated. As photosynthetic capacity and plant energy increase, plants begin to store surplus energy in lipids - plant oils. These lipids are the building blocks used to build plant protection compounds, called plant secondary metabolites (PSM5) or plant essential oils."
From here:
http://bionutrient.org/audio/2013_soil_nutrition_conference/2-Crop-HEALTH-Transitions-John-Kempf.pdf
Every plant makes its own food. The leafs are very important for this process so removing them is the same as reducing the food the plant needs to thrive! Proper soil will have everything the plant needs other than water. If you are growing in hydro the bottled nutes are replacing what the soil biology does. If you pour chemical nutes into soil you are killing the biology of the soil and will require you to continue to pour chemicals into the soil.
As long as the Rhizosphere is happy the plant will be healthy. Removing the one part of the plant that is responsible for feeding itself is counter productive. Nutes do not directly feed the flowers, they feed the leafs who in turn feed the flowers.
Any how, that is how I understand it! And I have to believe it after seeing the growth in the forest where no one has ever removed parts of plants thinking it will help them! Same with the pear, apple and cherry trees in my yard. If I were to remove the leafs I would not get a ton of fruit from them and my dog would not have the runs all summer.