Elmo wrote:
On Sun, 25 Apr 2010 17:06:15 +0000 (UTC), Elmo wrote:

Mostly, I'm left with huge tangles of poison-oak stems ... so I ask ...
WHERE does weed killer get INTO the plant and how?

This journal article implies only the leaves can uptake the glyphosate ...
both the underside and the upper side ... but HOW do they do that?
http://www.jstor.org/pss/4043711

What is the mechanism of uptake?

Bear in mind, leaves act like a child drinks from a straw ... i.e., water
transpires OUT causing a vacuum which brings water and nutrients in from
the ROOTS ... but glyphosate isn't applied to the roots ... it's applied to
the leaves.

It's all very confusing ... if the leaves are transpiring OUTWARD, why
would they suck in the wet glyphosate? What's the mechanism to suck INWARD
water from the leaf?

Same reason your fingers get all white and wrinkly when you soak them in
water...transpiration isn't the only process goin' on. Moisture on the
leaves is more accessible, I suppose, so it crosses cell membranes more
quickly than the moisture coming from the roots. The chemicals in
herbicides might do so more quickly...