Transport of auxin is usually from physiological apex to physiological base.
In stem it is basipetal while in roots it's acropetal
The transport aboveground should be in my opinion rather neglectable. Auxin in the root apex is transported in the so-called reverse umbrella (shape of transport pattern) ... that is: to the root meristem it goes down in the middle (in the center of the stelle - imagine the handle/shaft of the umbrella) , it goes down and crosses the quiescent center and there it is distributed laterally.... that is the time-point when the auxin starts to turn around and starts to rise up (turns around and fan out like surface of the cloth of the umbrella)... and it follows the direction to above ground ... it follows circumferential paths near - around the surface of the root tip - there it is paralel to he downstream which is in the center.
However this upward stream is going only for few milimeters or centimeters and it is once again slowly turned around - making whole loop - inside from the surface to the central axis (umbrella shaft) and going down again (not part of an umbrella :-)) ).
... excess of auxin is degraded.
there indeed is some additional synthesis of auxin in the root apex, but under normal situation - it would never escape the umbrelike loop around the quiescent center.
That is normal situation.
Under some situations, like the reverse flow in the floem of the trees in the spring - is in my informations - one of the rather rare situations, when auxin goes up (I had read just one report of such situation).
But generally speaking, as long, as the upward stream is defined by xylem flow (normal situation) - there is close to nothing of auxin in there and there should be close to nothing of auxin transport upwards..
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