Sassafra Leaf Morph distribution

Katie Westin kwestin1
Wed Dec 8 11:18:08 EST 1993


In article <2D0645D3 at coursmtp.nrc.ca>, RossN at imb.lan.nrc.ca wrote:

> This has probably been stated before, but here goes. In my (non-scientific)
> observations of maple and oak trees of eastern Canada, I have noted that the
> more light a leaf sees the deeper the lobes on the leaf. Shaded leaves of a
> mature maple are more "rounded" than leaves from the top of the same tree.
> Could a similar phenomenom explain the lobes in the Sassafras tree?  Could
> this be tested by shading selected branches on a tree at the beginning of a
> growing season and compare with unshaded branches?  Just my two cents worth.
> Neil
> (If my statements appear naive, it's because they are)

> In article <kwestin1-071293164330 at mac08.whartoncd.swarthmore.edu> kwestin1
> writes:
> >Two undergrads at Swarthmore College are looking at the distribution of
> >three leaf morph shapes over a range of trees, species Sassafras albidum.
> >We've found a strong correlation between percent unlobed leaves and age -
> >the older the entire tree (not just the branch), the more unlobed leaves it
> >has.  A literature search has turned up very little and we're brainstormed
> >out.  Any ideas, however wild, entertained!  Can _you_ think of a reason
> >for the correlation?  Responses, questions sent to
> >kwestin1 at cc.swarthmore.edu   Many thanks!
>  

When we undertook this study, we looked at correlations of sun and shade on
percent lobing and found none.  However, our data were not the best, and
I'd like to take another shot at it next season.  The whole project was
inspired by our work on phenotypic plasticity, which is why we hoped sun
might play a role.

Now it turns out that the leaf shape is determined in the bud; i.e., a year
in advance.  So I can't see how microenvironment selection could confer
much of an advantage.  This darn tree shoots down every great suggestion I
hear.  Thanks for your input, and remember, I'm probably more naive than
you are.
-Katie Westin
Swarthmore College



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