I have a question about the perched water table.I have grown many plants in pots.Especially chillis.Millet has mentioned the pwt is not conducive to root growth but i have taken chilli trees out of their pots and the whole of the pot is full of rootball.So,they must move into the pwt.I presume if you let the mix dry out enough,the roots will then be encouraged to search down into the pwt for the water they need.Am i right here and would citrus follow the same path if the top half of the mix is allowed to dry before watering? Therefore,wouldnt watering from below via a wicking action also be a good way of encouraging downward growth of the roots and therefore root colonization of the pot? cheers

Well,
sure!
Usually the potting mixture will dry from top to bottom, so the pwt is no myth, it's simply normal or common.
So the roots go downwards, because won't gather in the top of the soils, as moisture will deplete here first.
so the roots go down, were the moisture logest persist, in the pwt
So many potting systems for growing young plants and encourage the rootgrowth take advantage of this, and use this priciple for the root forcing system, which should encourage the roots going down....

But: I grow my trees in Seramis here I only find a ring of feeder roots in the pwt, because I have less free water in the bottom, as the capilary effect of the substratum will lessen the pwt effects.
But in many other growing medias, we have a significant effect on root development by the perched water table in the pot.

How the pwt affects a plant depends on the individual species/cultavar. Millet is normally discussing how it affects citrus, and they will not tolerate excessivly wet conditions. There are many plants that do just fine their roots are submerged in water. Every plant has it's ideal growing conditions. I am not sure about chillis.

Because the PWT constantly has an elevated level of water, it therefore also has a constant deficiency of oxygen. I would not recommend maintaining a dry upper container, to force the roots down. There are roots that require water and nourishment in all levels of the container. Because it is natural that roots grow down in a container, they don't require any additional pressure. - Millet