I would argue that you are removing the plants biggest root. It's still functioning and therefore feeding the plant. Removal is weakening the root system.
You are also recommending that a Newbie completely bareroots a young cutting and starts fiddling in a delicate root system with scissors. Even if the operation is a complete success you have provided at least couple of wounds for bacterial/fungal attack.
Then of course the plant needs to be re-potted. How often do we hear of plants suffering from shock after a Newbie has had a go at re-potting? So the plant not only has a setback for a few weeks but you have diminished its ability to recover by depleting its root system.
Far better, if necessary to separate sprouted cuttings, to remove them carefully with as little root disturbance as possible, ie maintaining the maximum medium in the rootball. The plant will probably suffer zero shock and will still have all its systems intact, as such it should romp away.
I meant the old root won't serve the same functions as the new one since a) it was cut off and b) it is no longer growing so it won't provide any stability. The old root is probably able to absorb some water, but I don't know if absorbs the same as a new one would.
Going back to Fred's point about root disturbance, when I re potted an adelae cutting that had already grown new roots to give to a friend, it suffered severe shock, despite the procedure being done as carefully as possible.
The old root has damaged root hairs from its being removed from the original plant, so no it doesn't have the same absorption capacity as a healthy new root would, but it does have enough to keep itself static until a new plant forms, much as in the same way a leaf cutting can osmotically absorb water to keep itself alive (as it's not helping support a whole plant anymore it doesn't need the high absorption capacity, hence why root cuttings are possible). And cutting the root into smaller sections can not only speed up the new plantlet's production of its own proper root system, but it can also encourage the original root to sprout more plantlets, up to the point where it no longer has enough viable tissue to do so. In some ways the cut root acts like a somatic seed, providing nutrients while the new plant grows out and establishes itself.
Everything has a reason, whether big or small. Never underestimate the power of what is or is not.
There is far more to everything than meets the eye.
Edit: I have a little more time now that I'm back so.....
Question, Does the root lose its hairs because it has been removed from the plant or because of the handling?
It's not just keeping itself static, it is generating a new plant (or more).
I have found that around 1.5" is a good size for root cuttings. I've only ever used the technique on D. regia.
I find it interesting that a root that is behaving like a root ie, supplying sustenamce should suddenly be described as being like a seed.
It's like a bald parent who is sustaining his/her (women can go bald too) offspring using money out of the bank rather than from earnings. The money is just as good no matter where it came from.
A root supplies sustenance to the plant, this damaged one is doing exactly the same only it's drawing the nutrients from a reserve. I see no reason to stop saying it's a root
If it looks like a root, acts like a root, smells like a root it's a ROOT
Last edited by fredg; 03-13-2016 at 02:07 AM. Reason: Additional