[VIPS] Ideotype question (fwd)

'Toby' H D Bradshaw toby at u.washington.edu
Thu Oct 12 13:48:46 EST 1995


In talking with poplar breeders, they seem to agree
that (empirically speaking) hybrid clones do not change their performance
rank much when going from single-tree plots to monoclonal stands.

I don't know if that means:

1) the crown geometry doesn't matter much in open vs. closed canopy, or 
2) the variation in crown geometry among the F1 hybrids typically tested 
	isn't sufficiently variable to give a differential response, or
3) some other explanation.

It seems intuitive (to me) that a tree with a few big proleptic branches and
vertically-tilted leaves (e.g. deltoides) is going to lose a lot more
growth when going from open-grown to closed-canopy than is a tree with a lot
of small sylleptics and planophile leaves (e.g. trichocarpa).  The lack of 
side light inside a stand must hurt the tilted leaves more than the 
horizontal leaves in terms of light interception, mustn't it?

It also seems intuitive that at least some trees have a plastic
response to the "extra" light available in the open -- I-214 is
a pretty rough-looking tree when open-grown, but of course is a
paragon of fine form in European veneer plantations.

However, since my intuition also tells me that the sun revolves around the 
earth, maybe my intuition isn't worth much! 

-Toby Bradshaw
toby at u.washington.edu

On Thu, 5 Oct 1995, Don.Dickmann wrote:

> Date: Thu, 05 Oct 95 10:00 EDT
> From: Don.Dickmann <22484DID at msu.edu>
> To: toby at u.washington.edu
> Subject: Ideotypes with/without crown clo
> 
> My inclination is that canopy geometry traits are relatively nonplastic, e.g.
> a genotype with a narrow crown will show this trait whether planted in
> isolation or tightly packed in a plantation.  That is not to say that traits
> will not be modified somewhat due to competition, but the relative standing of
> a given genotype in relation to other genotypes will remain about the same,
> regardless of how it is crowded, i.e. there will be little genotype x
> environment interaction for canopy geometry traits.  That would be my
> hypothesis, anyway, but it certainly needs to be more thoroughly tested.
> 
> Don
> 





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