resin canals analogous/homologous to secretory canals??

[Richard Jensen]

My guess is that these structures should be viewed as analogous, not
homologous.  there is a great diversity of secretory structures in
angiosperms - laticifers in Euphorbiaceae and Asteraceae, oil canals in
Apiaceae, etc.  Some of these are derived from single cells in the
mesophyll of the leaf and others are derived from a series of cells.
These cells are often idioblastic and I'm not sure that there is any way
to make a claim that the development of a latificer in the leaf of a
poinsettia is homologous to that in the leaf of a dandelion.

The resin canals in conifer leaves apparently are more complex structures
with a lining of secretory cells surrounding the lumen.  In fact, we can
question whether the leaves of conifers and angiosperms are homologous.
This seems a more fundamental question that must be addressed first.

Richard J. Jensen      |   E-MAIL: rjensen at saintmarys.edu
Dept. of Biology       |   TELEPHONE: 219-284-4674
Saint Mary's College   |   FAX: 219-284-4716
Notre Dame, IN  46556  |