Hiho - how does a plant replace the lost fanleaves? Is it growing the fan-leaves back? Or is it promoting the new shoots instead?
And if new shoots are blocked from light - will they grow big leaves? Are the shoots becoming thinly & elongated in order to avoid the shade? Are these light deprived shoots having 9-fingered up to 13-fingered leaves or just erratic 5 to 7-fingered ones? Will the internodial length be longer or shorter in this case?
And finally, what's the function of auxins in stems & stalks? Some of the answers to these question may serve as insight into when and how one should/could remove fanleaves....
It's because plants can sense the light which is thrown at them. Plants do everything to grow towards light.
In an outside scenario - a plant will get the same luminosity basically everywhere because the sun shines from different directions E-S-W and with such a sheer force, it can penetrate leaves multiple times and still be strong.
Indoors - not so much - mostly because of stationairy lights lacking the 550nm (green) bandwith and also, because of diminished strength due to distance.
a lemming can be a savage standalone fighter - BEWARE!:
There's people out there that argue that some forms of stress will even increase potency or dry weight - supercropping is one such technique. But it may also be just broscience.... The underlaying rationale is that cannabinoids are a shield to thwart off insects - or other herbivores.
If a plant becomes attacked/damaged it may respond by increased resin production.
Plucking away some fanleaves is nowhere near the stress level than when you do topping. Topping - esp. the first one on the main stalk - does collapse the internal fluid pressure and a plant may need days to recover from that.
Thing is, just keep on growing and keep an open eye for your plants - experiment with different techniques and simply learn by experience. If you think you've got the time you could do a bit mainlining because this will give you alot of insights of how cannabis acts when you heavily prune/defol.
Another thing to realize is that several plant manipulation techniques do have a preferable window of time when it's best to use them. With defol it would be after the stretch is mostly finished - but you can do so also in early veg - for example the bushy plant you've shown some pages before is leafy as hell - I would've used LST to lay it out as much as possible then defoliated all the bottom & inner fanleaves away so you'll get stronger new shoots.
What you're essentially trying to create in veg is to have as many nodes as possible - because these are the sites where later buds do form.
These nodes are much more important than fanleaves - esp. because fanleaves can become defunctional as a plant progresses from veg to gen. The colas also do a tremendous amount of photosynthesis at their own - via the sugarleaves.
Alot of growers are actually looking out for strains that are less leafy - because these are more easy to grow. But does it automatically mean these strains will net lesser? Absolutely not. I've grown less-leafy phenotypes which did harvest significantly more than their leafy counterparts from the very same packet of seeds.
Because a plant can only do a specific amount of photosynthesis and anything beyond that is just a waste. Search "Daily Light Integral" & "Light Saturation Point" to learn more about this.
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Cheers