Auxin and bud dormancy?

Lorine S Horvath lhorvath at plains.nodak.edu
Wed Dec 6 10:40:52 EST 1995


I recently got some surprising results, and I would like to get some feed 
back on them.  I am studying the control of growth in adventitious root 
buds of leafy spruge.  These root buds are normally quiescent under 
normal growing conditions.  However, if a root is separated from the rest 
of the plant (or the above ground portion of the plant is destroyed), the 
root buds break quiescence and begin to grow.  In order to determine 
where the signal to grow originated, I systematically removed portions of 
the plant, and followed budroot bud growth.  As auxin (or auxin cytokinin 
ratios) seemed to be the most likely signal, I initially removed the 
apical meristem as well as all the axilary buds along the stem and crown 
(leaving the leaves, stem portion, roots and root buds).  Surprisingly, 
this had little effect on the growth of the root buds.  However, when I 
removed all the leaves along with the apical meristem and axilary buds, 
the root buds all along the root broke quiescence and began to grow.  
When I Removed just the leaves and the apical meristem, only the root 
buds that were very near the surface of the soil began to grow.
	My question to the world is: Has there been any other reports of 
key regulators of bud dormancy/quiescence that are produced in the leaves 
(or appear to be initiated by leaf loss)? Does anyone have any 
suggestions as to ways to ID the signal?  (I have tried using agar 
bridges between the severed root sections with no success which suggests 
the signal is not capable of diffusing through agar.)  Any help will be 
appreciated!

Dave Horvath
USDA/ARS/BRL
Fargo, ND



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