From my experience.
When I buy Cryptocorynes in a shop they have
very long petioles
but in my well ligtened aquarium they become
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)
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.
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