Yes, again, I understand that leaves work for the whole plant, but the question is, do they work for every part of the plant equaly efficiently. It is well known that branches that are shaded don't grow as strong and buds that are shaded don't grow as big. I don't know why you think it's unreasonable to consider one possible explanation being that most of the energy gets used by cells near where photsythesys is happening and long range transport is not so efficient.Your question implies otherwise, which is basically asking what happens with photosynthate. Look into the phloem pathway for example.
Here you go: http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect19.htm
Transport in plants occurs on three levels:
As the last sentence says: "This explanation is very simplified - scientists are just now discovering the subtle details of phloem movement in plants". Nobody completely and exactly understands photosynthesis as a previous poster suggested, it is however a well-known fact that all leaves work for the entire plant, not just the part/fruit they connect too.
- the uptake and release of water and solutes by individual cells
- absorption of water and minerals from he soil by root cells
- short-distance transport of substances from cell to cell
- loading of sucrose from photosynthetic cells into the sieve tube cells of the phloem
- long-distance transport of sap within the xylem and PHLOEM
- this is a WHOLE PLANT phenomena - transport of photosynthate from leaf to root
Photosynthate is simply put energy harvested from the sun, stored in sugar molecules which are transported and used throughout the entire plant, everywhere where energy is needed for cellular processes (creating stems, leaves, buds, and roots).
The people who think they notice a yield increase just have too many plants or bud sites packed together. A fuck up than can be partly unfucked by removing some leaves. I have no doubt some people with some strains actually are able to push yields to a max but in general it's just a bad idea and completely unnecessary to get max yields.
I'm definately not an advocate of radical defoliating, but if you have a situation where you have lots of leaves covering your buds (for example in SCROG GROW), I think it might be reasonable to try and remove some of those leaves, leting leaves that grow out of the buds do more work.