Confused about root pressure

Question

During transportation of water during root pressure if water can not pushed up all the way to the top of tall trees, then what happens to tall trees such as the giant redwood trees. Do they just not grow in dry places that don't get a lot of rain, or do they just stop growing to the point where water can no longer fight gravity?

Answer 1

Redwoods don't have deep root systems, although they can be quite extensive.  They get the majority of there water from the atmosphere itself.  Water, in the form of fog, will condensate on the needles of the redwoods and actually be absorbed that way (through stomata or stomates).

Redwoods are the only tree I know that works this way (and why we see them along the coastlines of California and not in dry, arid regions.)

Answer 2

Good explanations on water pressure, etc.  I agree that the large trees get much of their water from absorption through the stomata on the needles.  My wife and I visited a nature reserve in the desert about 200 miles north of Santiago.  This reserve was located largely on the slopes of mountains.  These slopes led to the seashore and the area was known for its morning fogs.  The reserve had trees growing that were only found in the south of Chile about a 1000 miles from the reserve. The fog was being absorbed through the stomata and a diverse forest of shrubs and trees was growing far from their normal area.  

Answer 3

There are other mechanisms at work including "Transpiration Pull" which is the main phenomenon driving the flow of water.

The maximum root pressure measured in some plants can raise water only to about 20 meters, and the tallest trees are over 100 meters tall.  As an aside, if a pure vacuum was pulled above a closed column over water, the "weight of the atmosphere" (14.7psi) would only be able to push water about 10 meters.

Also look up epiphyte.  It's very interesting.  In a rain forest, ephphytes in the forest canopy decay and leave behind a soil into which the tree sends roots (from the branches).  The base soil at ground level doesn't have enough nutrients to support such a big tree by itself.