Date: Tue, 19 May 1998 11:06:30 +0100 (BST) From: "Dr W.R. Tribe" <wrt20@cus.cam.ac.uk> To: cp@opus.hpl.hp.com Message-Id: <aabcdefg1706$foo@default> Subject: (Dumb?) questions about anthocyanins etc
Hi everyone,
I've been puzzled a bit by anthocyanins (there was a thread in the list
sometime ago, and references to an interesting piece on them on the net).
Can anyone relieve the misconceptions of an ignorant physicist?
i) Someone asked a while back about identifying anthocyanin free cobra
lilies in the seedling stage, and the answer that came back was that they
should not display a red tip when the pitchers first emerge. Similarly in
sarracenia, where a "normal" plant pokes up very red pitchers at first -
presumably due to the presence of anthocyanins - but then after a while
the red colour dissipates, only returning in the coloured varieties after
exposure to light. Now I understood that anthocyanins became red on
exposure, so;
Why are the pitchers red at first, when there has been no exposure?
Where does all the anthocyanin go when the young pitchers change
colour from red to green (seemingly quite rapidly)? Is this a chemical
change?
ii) Is it well established that anthocyanins are the only agents
responsible for colouration in CP's? I'm sure there are a range of
different chemicals that come under this heading, but given the complexity
of plant organisms, I would personally find this extremely surprising.
iii) Is it true that strongly coloured varieties are less efficient at
photosynthesis? This may well be a stupid argument, but lets take an
all-red and all-green S. flava - the all green form absorbs in all
spectral ranges bar green, cuased by the chlorophyll, whereas the red
spectral region is denied to the photosynthetic process in the all-red
flava, the implication being that all other things being equal, the
photosynthesis is less efficient. If true, perhaps the relation between
colouration and light has evolved as a self regulating process? i.e. in
strong light levels the colouration reduces photosynthesis to the correct
levels automatically..... (Maybe this could be tested by comparing
the performance of an antho-free variety in the shade and in full sun..).
On a separate issue, when we are talking about introducing alien species
into our environment, it seems to me that we would be well advised to
consider the numerous ecological screw-ups caused by such approaches in
the past. The best example I've heard of is the cane toad in Australia,
introduced (I believe) to control some type of crop pest. It has no
natural predators (it has a very powerful skin toxin), breeds like a
rabbit, and also feeds on a whole bunch of other natural Australian
species, seriously threatening the indigenous populations, and
dramatically changing the ecological balance. For the sake of
argument, if we introduced a CP to a European bog, we might find
that it is really efficient at eating all the natural pollinators for some
natural species, which is the main food supply for some animal and so on.
I know this seems unlikely due to the plethora of insects, but when
humanity messes up (as it does far too frequently), it is often because of
seemingly correct assumptions which turn out to be wrong.
Cheers
Bill Tribe
Cambridge, UK.
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