How does an orchid "know" that it is pot bound?
 

I am wondering how an orchid knows when it is pot bound and therefore starts to thrive.

Does the plant have so many roots as to push out most media and make the pot more dry and ventilated?
This implies to me that orchids who want to be pot bound would prefer airier roots.

Does the plant simply have a plethora of roots when it is pot bound, meaning the state of being pot bound is a secondary symptom to a plant already in good health?

Does a pot bound plant have very good stability and feel so secure in its position that it feels comfortable to risk putting out a flower spike?

If you unpot a pot bound orchid without breaking its roots, and then repot it, why wouldn't it stay just as happy (aside from recovering from the shock of a repot)?

I am just wondering how and why the plant knows its pot bound, and why exactly this is beneficial to a plant.

I've read an article from an "industrial" grower, those with labs and a investigation dept. that an orchid with a flower spike (or also a keiki) is a stressed plant that feels itself at risk. So, the flower or keiki are mechanisms to propagate in case of the main plant dies.

Well, that is more along the lines of "couch potato" orchids (see this article). These are orchids that are always too comfortable and never feel any motivation to put out a spike.

It's why things like a night temperature drop, a little too much sun, deprivation of water and fertilizer on winter rests and so on cause a plant to feel small stress and want to make flowers.

However, if a plant is VERY stressed it may not spike at all- for example, a severely dehydrated plant or a very unstable plant may not want to spike. So there's a special little window of stress that will encourage the plant, but too much will probably keep it from spiking?
That's what my thought process is anyway.

An unstable plant might "think" that it is too risky to push out a burst of energy to make flowers, where a lightly stressed stable plant might "think" the risk is justified.

I think lots of roots mean it has a good store and means of getting water to sustain the flowers, since they're the part of the plant that loses most moisture afaik.

This is the article I was talking about.:)

I'm not sure how the process works but your "theory" makes some sense to me.:D

There's actually been a study showing that plants can 'sense' the size of a pot with its roots, though the mechanism is still unknown. Can't link the paper here, but here's a news article about it: Want bigger plants? Get to the root of the matter

This doesn't really answer your question, since in the case of these 'normal'plants in the study, being pot bound actually decreased the size and growth of the plant. Orchids like to behave in exactly the opposite manner...

The results of this study don't surprise me. All the work I've seen on root 'behavior' is quite amazing.Time lapse videos of roots show that that are poking and prodding and searching out the best direction to grow, seeking out the most nutritious areas in the soil. The way the roots move rather looks like a snake or other creature rather than a root. Roots can also sense if neighboring roots belong to kin (sibling) or to a stranger (but still within the same species), and plants can then behave differently depending who their neighbor is.

I have not seen that a pot bound orchid thrives any better or different than a non pot bound one. Case in point: a mounted orchid is not in any pot.

Spikes are for reproduction. When conditions are right, most any life form will reproduce. Even animals, insects, birds and so on will not "ovulate" if conditions are too stressful. In extreem ideal conditions too many young are born, leading to a population crash later on, usually due to over forraging.

If the plant is happy, you will get flowers, if not happy, no flowers. I do not think pot size has any thing to do with this.

I agree with Optimist, with the following addition: a plant needs mechanical stability in order to thrive. That's why it really helps to anchor a newly-repotted plant in the pot. Any slight movement of the plant (even from a slight breeze) will discourage root growth. Once the plant feels stable, whether that is grabbing the pot, spreading out its roots widely, or attaching to a mount, THEN it will put on vegetative mass and will bloom.

I have small phals in very large S/H pots, and their roots don't even touch the pot walls (yet), but there are lots of them stretching in every direction, and they are thriving.

Remembering that in the wild, an epiphite is not repotted again and again. It begins in the same spot on a tree limb and stays their its whole life moving only in its growth direction. We destabilize our own plants. Even if intergenaric or hybrid, it is still unnatural to be moved year after year. The most stable plant is one that is not repotted often. Putting it in a media that does not need to be exchanged and in a large enough pot for future growth is a good start.

If you think of it, the reason people repot is decaying media. I moved to rocks for this reason. Rocks don't decay. And the only reason people use small pots is the media stays too wet. Rocks do not stay wet, so a big pot is fine.

I think it's simply that the root zone of a pot bound orchid dries more quickly than a pot with a lot of space and media.