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Old 27-04-2004, 07:06 AM
hakimeh
 
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Default sugar transport in plants

i want know,plz, what does determine carbohydrate in which direction
transport or store and how does the leaf stop its carbohydrate
transport to a other parts of plant. and the other question is that
the carbohydrate storage of fuit is full and transport should be
supressed? thank you for your answering
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Old 29-04-2004, 06:13 PM
Iris Cohen
 
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Default sugar transport in plants

i want know,plz, what does determine carbohydrate in which direction
transport or store and how does the leaf stop its carbohydrate transport to a
other parts of plant. BRBR

As you apparently know already, leaves manufacture sugar all during the growing
season. It is transported wherever it is needed for further growth. In the
fall, with shorter daylength, all the sugar in the leaves is transported to the
roots for winter storage. Then the leaves fall. In the spring, there is a surge
of sugar transport back up the tree to the buds, which is why we collect maple
sap in the spring.
As long as the leaf is green and growing, it is making sugar & sending it to
other parts of the plant.

the carbohydrate storage of fuit is full and transport should be supressed?
BRBR


I think what you are asking is, does the plant stop making sugar when it is
full of ripe fruit? They are not directly connected, except that fruit is
usually ripe in the fall. The main reason leaves stop making sugar is short
daylength in the fall. In most tropical areas, there is a wet and dry season,
and trees prepare for the dry season the way trees in cold climates prepare for
winter. In the rainforest, where there are no seasons, leaves make sugar all
year long.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)
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Old 30-04-2004, 02:09 AM
David Hershey
 
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Default sugar transport in plants

(hakimeh) wrote in message om...
i want know,plz, what does determine carbohydrate in which direction
transport or store and how does the leaf stop its carbohydrate
transport to a other parts of plant. and the other question is that
the carbohydrate storage of fuit is full and transport should be
supressed? thank you for your answering



Plant physiologists often use source and sink terminology to describe
in what direction sugars are transported. A source is a
photosynthesizing leaf or stem in some species, such as cacti. A
source can also be a storage organ. Sinks are organs that require
sugars produced elsewhere, such as roots, flowers, fruits, developing
leaves and storage organs in the process of filling up.

If there are insufficient sugars to supply all the sinks, then it is
termed a source limitation. Source limitations are common when trees
produce large numbers of fruits. Fruit growers typically reduce the
number of fruits, termed thinning, to reduce the source limitation.

If there are insufficient sinks, then there is a sink limitation. Sink
limitations occur when conditions allow for photosynthesis but there
are insufficient sinks, such as growing shoots or developing flowers
or fruits. A sink limitation can cause a feedback inhibition that
reduces the rate of photosynthesis. Sink limitations can be induced by
removing all the growing points.

I have a 2 meter tall potted grapefruit tree that is kept indoors in
the winter. Its leaves become sticky from sugars. I assume that it is
caused by a sink limitation because there is no shoot growth in the
winter but conditions are fine for photosynthesis.

Webpages of interest:

http://www.google.com/search?hl=en&l...sink+relations
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