Date: Mon, 6 Jan 1997 11:09:07 From: SCHLAUER@chemie.uni-wuerzburg.de To: cp@opus.hpl.hp.com Message-Id: <aabcdefg80$foo@default> Subject: Re: Carnivorous Orchids
Dear Danny & al.,
> As far as we know the traps of all CP are leaves rather than flowers. A
> carnivorous flower would be selective against pollinators, provided that it
> offers a reward to visitors. Orchids do not seem to offer any reward and
> are therefore unlikely to have developed carnivory. Many do, however,
> exploit insects for pollination by mimicry.
The case with no reward whatsoever in orchids is not entirely true
(how could it be so in a family as awfully large and diverse as
this?). There are species producing nectar (i.e. nutritional rewards,
e.g. many of the spurred species).
Some species (especially of Stanhopeinae) produce and secrete
"perfume" which is collected by male individuals of certain insect
species (e.g. solitary bees) which pollinate them. The males in turn
attract their respective females with this olfactory lure for reasons
everyone on this list will be able to imagine...
Last but not least, orchids reward us by the beauty of their flowers
and several are in the meanwhile exclusively pollinated by _Homo
sapiens_.
> Does anybody know of mycorrhiza in CP? Might the absence of specific fungi
> be a reason for difficulties we have in growing certain CP?
Yes, perhaps. Maybe it is even the reason for the difficulties they
had in nature so that acquisition of carnivorous properties was an
evolutionary advantage. Lentibulariaceae, a family perhaps derived
from aquatic ancestors (Scrophulariales are parasitic rather than
mycorrhizal, anyway), seems to be entirely non-mycorrhizal. The
"extended caryophyllid clade" with _Nepenthes_, _Triphyophyllum_,
_Drosophyllum_, and Droseraceae contains naphthoquinones which seem to
"protect" from fungal contacts rather efficiently. The instance
of root fungi mentioned for _Nepenthes mirabilis_ may be the rare
exception rather than the rule. So at least the greatest bulk of cp
species seem to be essentially non-mycorrhizal. I have no information
on Sarraceniaceae, _Byblis_, or _Cephalotus_. No mycorrhiza could be
found in dried or living specimens of _Roridula_ although
Marloth has mentioned associated fungi. But on the other hand
_Roridula_ is only sub- carnivorous, either.
Kind regards
Jan
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