*Excess red and far red, penetrate.
Yes, it does, but to varying degrees. And this then causes specific effects and/or reactions in the parts of the plant receiving different (and perhaps insufficient) amounts and wavelengths. I've been doing research for what i consider to be a significant amount of time now (especially since i'm in the LED camp, where we have increased incentive to take note of spectral differences and specific wavelengths, since eliminating "wasted light" is one of the efficiency benefits of LED...). How much useful light actually passes through a nearly opaque top leaf? Two nearly opaque top leaves? Three? According to my own visual assessment: not very damn much! When i see wilting under-leaves, but everything else looks great, this tells me those under-leaves are Not getting enough useful light, despite the granted fact that certain wavelengths do indeed pass through. At some point, all the useful photons have been snared by leaf material; if any leaf material remains beyond this point, they are not getting enough light, which is where my previous comment comes from: spend energy to grow under-leaves which will never get enough light to contribute effectively, or snip them before the plant spends energy to grow something that cannot contribute (and thus causes detriment via wasted energy)?
Also there is the issue of insufficient horizontal space, in which case 'lollipopping' becomes more relevant. If your lamp can only penetrate, say, 2 layers of canopy... you don't need to spend harnessed energy to grow a third layer of canopy, because they won't get enough light to develop properly, and will therefore spend more energy than they contribute (and on insufficient development, for that matter). That third unlighted canopy is terribly inefficient, because it takes energy to grow something suboptimal, but is also unable to contribute as much as it spends or "sucks." It is a negative sum-total. An unlighted leaf consumes more than it makes, which is both inefficient and possibly detrimental to overall plant health. If you're burning ~90% efficient electricity to grow a <50% efficient plant... that seems not good, to me. I want as much of the energy as possible to be used as effectively as possible. Plus i like being able to access my soil, whether for watering or just poking around, so anything between the top of the soil and the screen, or perhaps my lowest useful canopy level (method depending), is really just causing problems and reducing efficiency overall.
And then we can head on over into mainlining territory, where, apparently, it actually matters which flowers come from which nodes. If you have a 2ft skinny branch with shaded leaves, which will likely only produce a "popcorn" bud, does that seem good to you? I'd rather have 32 colas branched from the lowest node, than a bunch of stem-spaghetti and popcorn everywhere.
It seems kinda ridiculous to get worked up over a useful technique, used by Others, just because you feel it's not helpful in YOUR situation.
If you have enough light in all the right places, keep everything! But most of us don't have that. So some of us try to maximize the efficiency of our configurations, by eliminating what WE feel is "wasted" energy. Yes, that energy "is consumed," but that is not the point: what is produced as a result of that consumption, is the point. If the energy my plant is receiving, is only being half-effectively used, that is inefficient, and is an insufficient efficiency rating, in my book.
If i couldn't read, and hadn't done research, i wouldn't even have an opinion on this matter. I'm only here BECAUSE i Can read, and Have done research, and have directly observed factors and results, related to this topic.
It's easy to see why some people would want to prune the inferior parts, which are expected to remain inferior, due to insufficient lighting for 3rd or 4th+ level canopies. Those photons don't just continue infinitely, they get harnessed. Below that, leaves aren't receiving light, and can't contribute, and can't develop, but still consume energy to be maintained. Eliminate that useless energy consumption, preferably before it ever grows, and what is effectively and efficiently harnessed by the rest of the plant, can be put to better use. Makes plenty of sense to me. ^^
