>To: plantbio at net.bio.net>From: tstanley at lamar.ColoState.EDU (Thomas R Stanley)
>Subject: Basal sprouts and energy budgets of trees (Q)
>Date: 11 Jun 1996 11:41:19 -0600
>>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
>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.
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.
>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?
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.
>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.
>>Tom Stanley - Wildlife Biologist
>NBS-Midcontinent Ecological Science Center
>Fort Collins, CO
>>Email: tstanley at lamar.colostate.edu
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
Marc van Iersel E-mail: mvanier at gaes.griffin.peachnet.edu
Department of Horticulture Tel: (770) 412-4766
University of Georgia Fax: (770) 412-4764
Griffin, GA 30223-1797