I think plants shouldn't be lightened
24 hrs a day, The photosynthesis has 2 phases. During days plants
accumulate the solar energy and at nights they produce new
----- Original Message -----
Sent: Wednesday, April 09, 2008 3:57
Subject: [Aroid-l] Petiole
Dear Wise Ones,
A phenomenon has come to my attention by
way of Jim Langhammer, who used to be a contributor to this list. He is a
trained botanist and life-long professional fish and reptile keeper and
expert. He is well known in the Detroit area (USA) since he is the retired
curator of reptiles at our zoo. The reason I point out this biographical
material is to emphasize that he is a close observer of the natural world and
one whose observations are to be taken seriously.
Mr. Langhammer has an aquarium of 70 gallons capacity
in which he has a culture of Cryptocoryne of the cordata complex. This
aquarium has been maintained almost undisturbed for a decade or two with this
planting and his results have been remarkable. His plants grow luxuriously
with total leaf lengths of around 18 inches (46 cm) at maturity, being perhaps
two-thirds petiole length and the balance leaf blade. The leaves are a rich
color and apparently in the peak of health. Water is changed two or more times
per week. The substrate gets no fertilization other than "mulm" from fish
wastes. Over the years illumination has been provided by a single cool-white
fluorescent bulb, 24-hours a day.
As it happened, a few months back he decided to switch out the
cool-white fluorescent with a gro-light type with a different temperature
profile. The reason for the change was to enhance the appearance of some
characin fishes in the tank, which was successful.
But over the next few weeks after the bulb switch the
plants experienced a dramatic contraction in the petiole length. The leaf
blade dimensions did not seem to change much, but the overall leaf length is
now less than about 10 inches (25 cm). Old leaves have not died and this is
not simply the emergence of new leaves adapted to a new illumination regime.
The petioles have contracted on the order of 50%, presumably because of a
shift in the intensity or color temperature of the illumination. The petioles
are not bent or otherwise distorted; just shorter.
The growth habit of the leaves, it should be noted, has
changed as well. Under the old regime the leaves tended to strive upward, as
if seeking light. With the new light they tend more toward a horizontal leaf
blade orientation. This behavior could indicate a trigger associated with
phenomenon was reported earlier by another Crypt fancier who had received
offshoots from the Langhammer clone. But, at that time, we attributed the
episode to the usual adjustment problems associated with radical change in
culture and we did not have the controlled observation that we have in this
case. The other grower was not certain that the leaves were not just new
growth, for example.
references to plant contractile activities in certain roots (dandelions,
daffodils) that serve to pull bulbs or crowns into the soil, and in tendrils,
which coil and contract to pull vining plants like cucumbers toward supporting
Has anyone on the list
read about or observed such contractile behavior in Aroids, especially in
leaves? We wonder, naturally, if a return to the old illumination regime would
result in reversal. We wonder what possible physical mechanism could account
for shortening on this scale.
I might add, we wonder if we are crazy. If you think I'm crazy I won't be
offended. Others have made that inference in the past.
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