Subject: Basal sprouts and energy budgets of trees (Q)

From: [email-masked] (Thomas R Stanley)
Date: 11 Jun 1996 11:41:19 -0600

Greetings:

I have a question about basal sprouts (suckers?) and the overall energy budget
of a tree, and would like to tap the expertise of the readers of this newsgroup.  
Suppose a deciduous tree sends up a sprout from its base which is allowed 
to grow until leaf fall, when it is pruned off.  Initially, there is an 
energy cost to the tree since it has to construct leaves, a stem, etc for the
new sprout.  Eventually, the sprout becomes photosythetically active and 
is able to contribute to its own rapid growth.  I have two questions: 1) Does
the tree have to continue to supply the sprout with energy throughout the
growing season (until fall, when the sprout is pruned), or is there a point
during the growing season when the energy produced by the sprout is sufficient 
to support its own growth (or even has a surplus that it can contribute 
to root growth or storage for winter)?  I realize the tree will have to 
supply the sprout with nutrients, etc.  I'm concerned here only with energy.
2) If the sprout produces a surplus of energy, is the surplus (integrated
over the growing season) sufficient to repay the tree its initial investment
of energy in the sprout?

I realize there are probably no simple answers to these questions, since 
factors such as shading or herbivory can affect overall energy budget.  
Nonetheless, under ideal conditions of full sunlight and no herbivory (or
any other complicating factors), there must be some information on the 
relative costs of sending up sprouts.  BTW, these questions came to me 
while deciding whether to prune the basal sprouts of my ornamental ash
now, or waiting until the fall.  The ash is relatively new and needs to 
grow roots.  If the sprouts cost too much energy (integrated over the 
growing season) I want to cut them back now.  If, however, they will
produce a surplus of energy, I'll wait until fall to prune them (so 
I'll reap the benefits while incurring no overwinter maintenance costs).  
I'd appreciate any thoughts on the matter.

Sincerely,

Tom Stanley - Wildlife Biologist
NBS-Midcontinent Ecological Science Center
Fort Collins, CO

Email: [email-masked]

---

From: [email-masked] (Marc van Iersel)
Date: 12 Jun 1996 11:37:43 -0700

>To: [email-masked]
>From: [email-masked] (Thomas R Stanley)
>Subject: Basal sprouts and energy budgets of trees (Q)
>Date: 11 Jun 1996 11:41:19 -0600
>NNTP-Posting-Host: lamar.acns.colostate.edu
>
>
>Greetings:
>

At some stage during the growing season the sprout should become
self-sufficient, as far as carbohydrate supply is concerned.  Exactly how
long that would take is hard to say.  It should also start exporting sugars
to other (growing) parts of the plant.  These sugars could be exported to
the roots, new sprouts, flowers, or fruits.

>over the growing season) sufficient to repay the tree its initial investment

This question is difficult to answer, but my educated guess would be that
the tree would eventually get more carbohydrates back from the sprout, than
that it initially invested in it.

>Email: [email-masked]

The bottom line is that there is indeed no simple answer, as is the case
with most good questions.  Most plant try to keep a balance between their
root and shoot growth.  If the plants really has an inadequate root system,
shoot growth will probably be slow.  If you let the sprout grow out, the
tree will probably respond by increasing the size of its root system.  It
needs to do that to maintain a proper balance between root and shoot size.
After you prune the sprout this fall, the plant will probably have a
relative abundance of roots, because it does not have to support the sprout
anymore.

Marc

Marc van Iersel			E-mail: [email-masked]
Assistant Professor		
Department of Horticulture	Tel: (770) 412-4766
University of Georgia		Fax: (770) 412-4764
Georgia Station
Griffin, GA 30223-1797