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----- Original Message -----
From:
t*@us.henkel.com
To: aroid-l@gizmoworks.com
Sent: Tuesday, March 18, 2008 5:03
PM
Subject: Re: [Aroid-l] Phototropism
Hello, I'm not so into
Cryptocoryne, but these bought in a shop really look like like growing in a
shallow water where the leaves flow free. They couldn't be grown emerse, then
they would be more stiff
Thanks for so long
info
Marek
This is a different sort of
phenomenon than what I am speaking about. Some, perhaps most species in this
genus do become very different in leaf morphology when grown under different
lighting and planting conditions. The again, sometimes just the opposite
happens; the leaves and petioles elongate from what you buy at the store or at
an auction. In general, however, Crypt leaves tend to look more like your
"before" pictures. My bet is that those had been growing emerse (with leaves
into atmosphere), while yours look submerged. That alone is enough to account
for how different they look now. If you look at the right-hand picture of the newly-purchased plants on
your site (the ones in the mesh baskets) http://www.wschowa.com/abrimaal/araceum/cryptocoryne/wendjahn.htm
you will see the sort of situation that
can lead to a "flip-over". If that plant were planted in a shallow-immersed
situation, where the leaves tend to splay across the water surface, that
middle leaf could well end up with its underside exposed to the sky. We are
not speaking here of an event where the petiole has folded, kinked, or
twisted. Those conditions would obviously result in a physical problem for the
conduction of sap containing soluble foodstuffs that could well lead to the
plant sacrificing that leaf. But because the petioles tend to be rather
flexible in this genus, the chances of ending up with an inverted leaf are
good. Judging from the lack of
responses I am thinking that the list does not know the answer. If I think of
all the leaves I have ever seen, unless a plant has suffered damage, all the
leaves want to be more or less horizontal. There is an upper leaf surface and
a lower leaf surface. The upper leaf surface may have a thicker skin, perhaps
with a waxy coating, or a darker color to deal with the stress of being in
direct light and more exposed to the elements. The underside is specialized by
having gas-transport structures, perhaps hairy features, and who knows what
else. The leaf may be exactly horizontal or may prefer to orient itself at
some angle (up or down from horizontal). Or it may even change as the leaf
matures. But this presentation to the world is a characteristic of the plant.
And it is always directional in higher plants. Algae and such may be
different. At the same time leaves
are typically translucent. This means that if you place a leaf between you and
a light source you can detect the light coming right through the tissue. To be
sure, some wavelengths have been filtered out, which is why the leaf looks
green (or reddish, or brownish, etc.). But the same sort of filter is in place
if you look through the other leaf surface. It still looks green, meaning that
light has been gathered and filtered. Is light coming up through the leaf
underside useful for photosynthesis? If not, why not? Don't think I'm pressuring anyone for answers. These
are just the questions I throw out because they bug me. There are many
unexplained phenomena in the world. Sometimes I think there are more mysteries
than there are answers. I am curious. Ted.
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