what happens when a plant gets rootbound?

sup people, I was just wondering what happens to a plant that is rootbound. Does it die, does it eventually suffer deficiencies, what really happens when the plant gets to that point?
My guess is the plant gets stunt and stops growing but is that all?
thx

That'ds about from my observations

The condition of being root bound is often seen claimed as ''too many roots for the container'' little-soldier, but in actual fact, how many roots there are, isn't a factor. What happens, is the roots grow out to the internal sides of the container; an then, finding the growing to be easy and fast in between the inner wall of the container and the dirt, they all start following the same general path.
Round pots are the worst kind for causing root bound conditions because the circular nature of the smooth wall never re-directs the roots' growing tips inward;
the growing tip is genetically programmed to grow straight by default; and gets deflected little by little, along the smooth interior of the pot: but never cuts back into the body of the soil itself.

At first, it's a good deal to the plant, and a good situation for the roots: they can expand quickly to feed an initially small plant. The inside wall of the pot makes growing easy, because the roots only have to push the soil away to one side; the inner wall of the container acts as a brace, and helps them plow through swiftly; pushing the soil aside easily.
On the other hand, the soil is right there- right alongside the roots: to the inside, above, and below... they throw out many little feeder roots, and draw all the nutrition they want from the soil.

But as the growth progresses, the situation degrades.

Soon, there's more mass of plant to feed, and maintain; both above and below the soil. The roots continue on and on: following the path of least resistance: but are increasingly forming an airspace that separates many of them from contact with soil; this due to their own expansion, racing around and around, between the soil, and the pot wall.

The same pot wall that made the growing easy, because it created a demarcation line between the soil and itself, now provides a smooth surface for water to run down beside, before it soaks in, and for excess atmospheric air to invade, dehydrating the feeder root hairs.

Also when watering's over & whatever water did get into the soil is sucked out by the roots, lost to drainage, & evaporation, that airspace is made even bigger: meaning less root contact, when the soil shrinks back a little. The dryer it gets, the worse the cycle is.

When the plant was small, rapid root expansion with minimal soil displacement, wasn't a problem. But as the entire organism gets larger, efficiency in uptake becomes more and more central to the system's continued vitality and expansion: as the growing root mass enlarges the low soil-contact, high moisture loss airspace between the pot wall and the soil, conditions approach a breaking point.

Things go on; the roots that do by chance get turned by the ones before them, push those previous ones aside, till a lot of them, are no longer in contact with soil at all. They undergo a change called 'air pruning' - they stop putting off the massive number of root hairs, the feeder roots, from the main trunks, and instead, the majority of the roots' surfaces are covered in protective, low moisture-loss, cells. Only the newly growing ones, snaking along between the previous ones, and the soil face, are able to justify high efficiency root hair generation. The ones they push aside to get to the soil face, successively harden off.

When the pots get watered, a lot doesn't go down into the soil, because the air space around the edges of the pot let the water run out between roots and the pot wall; making things worse.

They start showing general signs of reduced vitality; the main initial indication, is less response to being watered. When you water them they don't snap with refreshed growth. They start looking dehydrated, and under-fed, showing a general lack of nutrition to support the stage they're in; if they're flowering, the flowering diminishes or stops; if they're a large heavy foilage plant, they stop growing, and leaves start yellowing as they get raided for nutrients to carry to the top.

So the progression goes: at first, everything is tooling right along, there's nothing either unusually good, or bad.

Soon, the roots are in an optimum state for the conditions they find : they've expanded and filled all the space they can, swiftly and easily. Massive numbers of root hairs have filled the available space, interspersed with sufficient soil, to carry nutrition into them.

But then there comes, a rapidly advancing breakover: where the number of roots fill the best places between the pot wall and the soil. Watering them starts washing away even more soil from around them -and the lack of soil accelerates hardening off, air pruning of feeder root hairs, to reduce evaporation.

What had been a set of high efficiency uptake conditions, undergoes a rather rapid change: and as the roots harden off, the medium sized organism that was once fed by a highly efficient, adequate volume network of feeder roots, is now faced with a dilemna of its own creation: a large organism is being fed by an increasingly less efficient network of feeder roots.

In order to control moisture levels in the roots, hardening off happens: reducing uptake dramatically even during the short periods when water passes when watered - and the plant hasn't developed sufficient intra-soil root structure to support such large mass, because the ease of expansion, in filling the outer edges, led it to expend most growth into what was initially, a higher return investment.

The plant never can recover from this: it's set itself up. It's trapped trying to feed a larger mass, than any additional investment in roots will ever be able to feed, in spite of the fact there's plenty of soil around to be used. This phenomenon of racing around the pot walls without entering the soil is most famously found in round pots. The more gently curved and smoother the pot's walls, the more commonly root-bound conditions occur.

It goes around and around, continually trying to catch up, chasing the boundary region between soil, and pot wall. The situation degrades, until the plant is back to being fed by a small active root hair surface area, that never becomes more effective over time, and each additional watering adds to the problem: the central soil column, not being fragmented by roots, compacts: accepting less water per volume applied; ever more of what gets applied, runs out around the edges of the pot, where the roots have expanded the airspace there with their growth. The outer soil column, particularly at the bottom, fragmented from constant probing by roots, washes away little by little, particularly when the holes in the pot bottom are large: the roots press inward with yet another sheet of feeder hairs; but the previous sheet of them, now separated from soil contact most of the time, hardens off, yet again.

The plant's metabolism becomes controlled by the small amount of nutrition the plant's roots can derive from a boundary region, determined by the bottom, and to a lesser extent the side area, of the pot.
When watering occurs, the only place where there's much effective soil/root interaction for very long, is toward the bottom of the column of soil: this region in all soil columns, saturates, as the coefficient of drainage, and water surface tension, determines how much drains, and how much remains in a saturated volume at the bottom of the soil. The roots drive into this zone; if the saturated soil won't let gas exchange occur, they're forced to press up against it, but not go very far in; they remain on the surface, never expanding the total feeder root contact area. If the soil is well aerated, and not compacted by it's own weight and successive waterings, the roots will drive up into it more aggressively, but there always remains the fact, that the plant made a choice, early on: to try to exploit the high efficiency boundaries of the soil; and growth remains less than it would be if the sides of the pot were correctly configured to stop the plant from expanding that way.

Various methods are used to stop plants from defaulting to root expansion that causes root-bound conditions. There is a plastic liner sold that stops it, and people mix things like perlite, straw and burlap into pots, to make the roots follow paths throughout the soil better.

The liners that are sold probably work best. They're reusable, but I don't know what the name of them are. I grow aeroponically most of the time; when I grow passive hydroponically I use perlite & whatever's handy to increase the moisture retention; conditions aren't the same in hydro as soil regarding root expansion.

I'm busy nowadays; and don't have time to edit so sorry for typos, syntactical errors, sentences that dead end/ are repetitious, etc.

I think you might be talking about root pruning pots, like the air pots and smart pots. There's a nice discussion of them in the organic soil forum. They're supposed to prevent rootboundedness.

Eventually a plant will become root bound if not transplanted at some point. One thing that really helps, if your 100% organic, is to create zones, pockets and layers of nutrients for the roots to find and feed on. Doing this will help you grow larger plants in smaller pots without them becoming rootbound. In part the roots keep growing because they are looking for food. If there's a concentrated food source the roots will focus on that area until the nutes are exhausted then they will look elsewhere. Growers need to understand plants have been around longer than humans. Growers think they can out-do nature by bottle feeding or regularly dosing a plant in a pot with a concentrated nute solution so the plant is then fed globally. Follow natures laws and then the issue of a plant become rootbound fades away