Date: Fri, 26 May 2000 09:29:45 +0000 From: schlauer@chemie.uni-wuerzburg.de To: cp@opus.hpl.hp.com Message-Id: <aabcdefg1637$foo@default> Subject: re: Ancient Relatives / Sundew Evolution
Dear Ivan & al.,
> Here is an idea. Often we see tentacles in Drosera where only sticky
> trichomes should be, on the scape and bracts. I have seen a few times
> sundew malformities where flower styles and tentacles had been fused
> together, and also tentacles replacing styles.
Are you sure you have observed tentacles? The histological structure
of these is quite different from styles/stigmas, and tentacles are
usually not formed on the ovary.
> This has led me to believe
> that perhaps this is how tentacles evolved in sundews. Consider that
> styles are protein sensitive and capable of movement.
AFAIK, the styles of Droseraceae are not capable of movement. Have
you made other observations?
> Maybe the first
> sundew had simple glandular trichomes united with styles? If all this is
> true, then the same genes involved in construction of styles in Drosera
> will also be expressed in tentacle construction. Anyway, maybe we should
> not just compare trichomes with tentacles, but instead compare tentacles
> to styles.
I have a different theory (cf. CPN 26: 34-38, 1997): I believe the
glands on the bracts and calyces of Plumbaginaceae-Plumbaginoideae
(likewise Nepenthales but probably more primitive) represent suitable
models for the precursors of the carnivorous glands in Nepenthales.
These Licopolian glands are in turn probably derived from simpler
structures in Tamaricaceae. From their microscopic anatomy, these
multicellular glands are much more homologous to each other than any
of them is to styles or stigmas.
> I could collect herbarium material and seed of Silene laciniata for
> you to study if
> you are really interested.
Thanks, this is not necessary. We have several sticky species of
_Silene_ (incl. _Lychnis_) here in Europe, and I have already
examined some of them. I believe the function of sticky
inflorescences is similar to those in Plumbaginaceae: small crawling
arthropods are excluded from the flowers, which are thus more likely
cross-pollinated (by larger flying insects).
Kind regards
Jan
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