Plant leaves change pH?

[David Brown]

Jong,
        Don't forget your experimental controls. Have you
checked for some microbial (yeast, bacteria) fermentations
during those long exposures that may be changing the pH
rather than the action of the plant? Plant leaves have 
abundant microbial populations able to change your solution 
pH rather than the leaf plant cells.
                David
-----------------------Jong wrote-----------------------------------
Dr. Woo, Jong Ho
woo00 at chollian.net

Is it correct?
When i dipping leaves of tree in the solution of various pH levels with
various treating period( 1min - 48hr) i found the pH change of various pH
solution.