Taproot formation vs. growing conditions

Hi Robert,

In trees (grown in place from seed) how much does the development of a large taproot depend on environmental conditions vs. genetic potential of the tree?

I know that there are chemical signals sent out by plants under an insect attack that will be detected by nearby plants which then increase what defenses they may have, do you know of anything similar happening during drought stress?

Thank you not only for your time on the forums but the time it took to develop another resource for those of us interested in the natural way of things.

Very few plants produce a taproot. It's mostly the genetic tendency of the plant. Most of the water and nutrients are near the surface, so for most plants, it doesn't make any sense to create a taproot. In most forests, the nutrients are not deep in the soil. They're not even in the soil. They're in the life above the ground. PLants mostly adapt to the conditions they evolved to grow in, and for very few of them does a tap root make sense.
John S
PDX OR

The first person i heard talk about the power of taproots to burrow through solid rock also now informs me that you can cut the taproot when you put the tree into the ground and it will grow back (and straight down). I respect the man but i thought taproots, like the first shoot of the tree that grows straight up, can never be cut or the tree will stop developing vertically [up or down respectively].

Furthermore, i've heard Paul Wheaton say in podcast that taproots do not survive transplantation.

Though i've heard many say that most trees don't actually have a taproot as adults, i'm planning for a semi-arid climate in which some trees only survive if they can withstand long hot summers by reaching deep water.
Can someone weigh in on this? All the posts i've found on taproots make little of their importance but when you see the lone trees surviving in Moroccan deserts, their importance appears pretty damn critical to me, at least in some cases.
Can a taproot be cut and will it grow back?

Most fruit including apples, plums, quince, mulberries, etc. don't have taproots. Some, like pawpaws and madrones, do have taproots. Transplanting a pawpaw or madrone needs to be done with great care. It is much better to move it when it is young. I try to keep the taproot intact before moving it. I have about a 85% success rate with transplanting them. I don't cut the taproot. Deeper roots can tap the minerals deep in the soil. Most fruit trees have a combination of roots that are in the topsoil and some in the deeper soil. Paul and I disagree about this. I have transplanted innumerable mature fruit trees, so I am speaking about what I have felt and seen with my own hands. I think special methods for very arid climates makes a lot of sense. I live in a climate with abundant rainfall, so someone else will have to give you special information about that.
JohN S
PDX OR