"Bruce W.1" wrote in message
news:LtF6c.9871$F91.6868@lakeread05...
Please correct me if I'm wrong, and I probably am wrong.

Plants don't have a circulatory system. There is no circulatory loop
like with mammal blood. All moisture goes from the roots up. This is
caused by moisture evaporation from the leaves.

'Transpirational pull', yes, plays a part, there is also rootzone pressure
forcing the moisture up. Water *does* travel back down the plant via the
phloem, on its way back to the cortex portion of the root. Once the
sugar-laden water passes through the phloem laterally into the cortex
(osmosis), it then moves back out into the outer portions of the root for
its trip back up the plant. Trees and shrubs 'use' very little water to
sustain themselves-- I think about 8-10% in fact. The rest is either
returned to the rootzone laden with sugar or is transpirationally lost.


Theorhetically then, you could chop off a plant at ground level and
connect the stem to a vacuum suction pump and the roots wouldn't know
the difference, the roots would continue to grow.

*Some* plants have roots that would continue to grow, if there was suitable
levels of fuel (starch) available for the plant's roots to begin the process
of producing stem tissue.


Dave