I apologize if this has already been said, I haven't taken the time to read through all 46 pages of the thread.
It seems that the basic theory is that roots "exist only to take in nutrients for the plant", right?
That's partly true. But that's not remotely the only thing they do. The roots are an important storehouse for the energy created by the leaves (all the cells in a plant store energy in their vacuoles, but a huge portion can be stored specifically in the roots.) This is why growers traditionally focus on generating large root masses - this energy is tapped into during flowering/fruiting to really produce massive results.
The roots also produce the very important hormone, auxin.
I can't imagine how the effort to reduce or limit root mass would be beneficial. If you've got poor quality root mass (weak or dead roots), then getting rid of that with an enzyme treatment would be beneficial, but otherwise you're hurting potential yield.
You can certainly bring a plant through to the end of its lifecycle without a lot of roots, but you're not going to get as much yield from the plant as you would with a larger root mass.
Think about it: how many pro-athletes train strictly with IV-nutrition, bypassing their body's natural digestion system, simply because it's more "efficient"?
If you can boost a plant with foliar feeding, and hydroponics is efficient enough to support the same size plant with a smaller root mass (both of which we know to be true), wouldn't the optimal results come from maximizing everything in balance?
Plants aren't simple structures. Science describes the flowering process as one of the most complicated biochemical processes in nature and they've evolved over a vast amount of time to this form. To properly care for plants we have to not only pay attention to their individual needs, but the balance of those needs. If you increase CO2, you need to make sure you're providing enough light - else you're wasting the extra CO2 because the plant doesn't have the power to use it.
Now I admit I could be wrong. I haven't tested any of this specifically.
But the science just doesn't back up the theory. What we know to be true about plants says they use their roots for much, much more than simple nutrient uptake. The size of the root mass directly impacts the size and quality of the harvest in more ways than just its ability to take in nutrients. The stored energy (starches) are invaluable. That's why the plants store energy in the roots: they're saving up for the leaner months in the fall when they know they're going to be working extra hard to ensure they can reproduce and pass their genes on to the next generation.
Like the salmon in the ocean, storing energy as fat for the long, arduous swim upstream to mate and die - plants store up that energy in their roots so they can go huge on flowering and reproduction.
Anyway, that's the way I understand it. Plants may be able to survive without a lot of roots, but they need a large, healthy root mass to really thrive.
