Date: Fri, 20 Feb 1998 10:22:52 -0700 From: ricell@juno.com To: cp@opus.hpl.hp.com Message-Id: <aabcdefg678$foo@default> Subject: Re: Carnivorous Bromeliads
Rand,
Ok, first off, I apologize for what was perhaps a rather flippant
previous post.
While I do not believe there is an absolute "answer" to the possible
carnivory of any Bromeliads I do believe the question and search for the
answer are extremely interesting. In a black and white world of
definitions and labels it is clearly a shade of grey. Some say a very
light grey and others will say dark enough that it is not white.
Most people will agree that a plant that demonstrates the following
mechanisms is clearly carnivorous:
1. Specialized mechanisms to attract prey. 2. Specialized mechanisms to
capture prey. 3. Production of enzymes to digest prey. 4. Ability to
absorb and utilize nutrients from digested prey.
As you yourself implied in your post, not everyone follows such a strict
definition or label if you prefer.
The shades of grey, however, keep it interesting and not all standard CP
show all of these mechanisms. I don't believe anyone has demonstrated
any attractants to Utricularia traps, S. psittacina does not seem to be
very effective at capturing prey, and the effectiveness of digestive
enzymes in S. purpurea appears to be minimal. Some would argue that they
are carnivorous by "association" of being Sarracenia since other
Sarracenia meet all of the above criteria. What about Drosera caduca
then? Many plants that are not considered carnivorous are capable of
absorbing nutrients placed on their leaves however.
Brocchinia reducta produces a sweet smell that attracts ants and has a
waxy cuticle that is difficult to grip. It produces no digestive enzymes
but it does create an environment suitable for bacteria to break down
insects into absorbable nutrients (namely the water cup in the center).
It is capable of absorbing those nutrients. A lot of plants have waxy
cuticles and as stated above are capable of absorbing nutrients. Dead
insects are frequently found in the cup and experimentaly, plants "fed"
insects grow faster than those that are not fed.
Is it "as carnivorous" as Nepenthes? No. Is it "more carnivorous" than
Opuntia? I think so.
Is this carnivorous enough to be carnivorous? If you ask enough experts
I guarantee you will get answers on both sides. If Jan has not already
replied I believe he is on the NO side. What do you think?
The case for Brocchinia was originally made in:
Givnish, Burkhardt, Happel and Weintraub, The American Naturalist 124,
No. 4: p 479-497, 1984 if you are interested.
Richard Ellis "ricell@juno.com"
Boulder, CO
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