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Adaptation of Berberis Leaves to Sun & Shade

by Bob Harms  email-here
The response of leaf growth to conditions of sun and shade are essentially different for our two species. B. trifoliolata, with its rigidly trifoliate leaf structure, relies primarily on leaflet surface area and orientation of the adaxial surface to maximize/minimize sunlight exposure - but without changing leaflet length. B. swaseyi, on the other hand, primarily adjusts leaf structure - i.e., the number of leaflets and length of rachis internodes, without significant change in leaflet surface area.

Leaf length, width and length/width ratio differences are generally correlated with exposure.

Leaflet thickness is affected in both species, although more significantly with B. trifoliolata.

Table of Sun/Shade Differences

B. trifoliolata B. swaseyi
leaf structure sun shade sun shade
no. of leaflets --- --- usually 7 9-13
petiole shorter longer slightly shorter longer
length of rachis internodes --- --- shorter much longer
lateral leaflet length compared to terminal leaflet no difference
or slightly shorter		 clearly shorter no difference
or shorter
leaflet structure sun shade sun shade
adaxial surface strongly curved upwards toward edges flat somewhat undulate nearly flat
leaflet surface greatly reduced slightly larger no difference no difference
leaf thickness thicker thinner slightly thicker slightly thinner

The illustrations below are from a selection of typical leaves collected in late July/early August. A larger selection of leaf comparisons may be viewed at:

Berberis trifoliata

sun leaves shade leaves
sun leaflet X cut shade leaflet X cut
Typical B. trifoliolata leaves

Berberis swaseyi

sun leaf shade leaf
sun leaflet X cut shade leaflet X cut
Typical B. swaseyi leaves