Leaf Fall

Carl Adams cadams at sisna.com
Tue Dec 31 15:36:13 EST 1996

I'd reckon the ultimate reason is the different evolutionary histories
of the two species, the evolutionary history of chestnut has favored
early leaf senescence (effected through the production of absissic acid)
to conserve glucose while the oak is apparently able to offset the cost
of maintaining its leaves until later through increased productivity. 
Leaf area index (the area covered by all the leaves if you were to lay
them flat on the ground) is a better indication of the photosynthetic
capacity of trees as opposed to the height and girth of the branches and
trunk.  How does LAI differ between the two species, i.e. which species
has bigger leaves?  I would guess that the oak leaves are relatively
bigger or the LAI is greater thus enabling the oak to more effectively
capture the decreasing radiant energy of the sun.  Yea or nay?
Evan H. DeLucia
Department of Plant Biology
University of Illinois
265 Morrill Hall
Urbana, Illinois 61801

office:  217 333 6177
fax:     217 244 7246

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