Question

Rod Savidge savidge at unb.ca
Tue Apr 2 09:05:30 EST 1996


Oscillations in cambial growth certainly are associated with suitable
temperatures and water availability.  In addition, a correlation between
leaf production and annual ring formation has been repeatedly found in
trees of both temperate and tropical zones, the generally accepted
concept being that phytohormones (notably auxin) exported from the leaves
promote cambial growth.  It is also well established that flooding results
in elevated ethylene content in the roots of trees.  Leaf
abscission may follow upon flooding in response to increased ACC
(1-aminocyclopropane-1-carboxylic acid) being exported from roots to
leaves.  Whatever the cause of abscission (flooding, drought, late frosts,
etc.), the cambium of a tree losing its leaves generally enters
dormancy at least until new leaves are produced.  Thus, I agree with the
student that it would be reasonable to anticipate two `annual' rings in
1993.




In message 1 Apr 1996 16:20:53 -0800, Robert.R.Wise at net.bio.net  writes:

> Help,
>
> I got another "stump-the-prof" question today in plant anatomy
> class.  I told my class that growth rings in wood are due to episodic
> growth of the vascular cambium and its secondary xylem derivatives.  The
> growth episodes are influenced by temperature (i.e. summer vs winter)
> and/or water availability (wet vs dry).  A student pointed out that during
> the Midwest flood of 1993 many deciduous trees ceased growth and dropped
> all of their leaves and then resumed growth after the flood waters
> receded.  He then asked if that event would cause a "growth ring".  So
> now I'm asking you.  What would you expect to see in the wood of a tree
> that had undergone a mid-season cessation of growth that was not due to a
> water deficit or cold temperatures?
>
> Bob Wise
>
**********************************************************************
   Rod Savidge, PhD, Professor      |         E-mail: savidge at unb.ca
   Faculty of Forestry and         \|/
      Environmental Management  \   |   /     Phone:  (506) 453-4919
   University of New Brunswick  _\/ | \/_
   Fredericton, NB CANADA          \|/        Fax:    (506) 453-3538
   E3B 6C2                          |



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