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megan breuer mbreuer at saims.skidmore.edu
Thu May 2 17:49:12 EST 1996

student Science (b3631412 at KKUCC1.KKU.AC.TH) wrote:
: Anyone know that how C3 and C4 plant different?

	Well, to answer this question, you would have to take a look
at our friend the Calvin cycle.  Basically, the Calvin Cycle is a
process in which a 1-5 carbon element is broken down using PEP
carboxylace, and then undergoes a whole process which gives off ATP
and NaDPH2.  Anyway, the major differences between these two plant
types is that C3 plants cannot function in warm sunny climates because
they would lose too much water to the atmosphere.  The C4 plants are
especially adapted for hot climates such those in California, Arizona,
etc.  C3 plants do not have an uncoupler enzyme to break down CO2 into
PEP and Oxalic Acid (OAA).  They only have the Calvin Cycle, or C3
	The C4 plants can live in hot climates because they have an
uncoupler enzyme that can break down CO2 into PEP, which can then be
broken down into OAA, apsaric acid, and malate.  These special
functions take place only in C4 plants (and CAM plants).  Also, the
structure of a C4 plant is really interesting!  THe C4 has a layer of
cells known as the mesophyll cells, and other cells known as bundle
sheath cells.  The mesophyll cells are closer to the surface of the
plant, have little starch, and contain many thylakoids and grana, so
obviously, the light reactions would take place here, due to the high
presence of thylakoids.  The bundle sheath cells, however, are further
away from the atmospheric conditions, and contain less thylakoids and
grana.  Instead, these cells have a higher concentration of starch,
and are the sites of the dark reactions and Calvin Cycle.  This way,
the plant can live in a hot climate and still retain enough water and
nutrients to survive.  The CAM plants have a really interesting cycle,
too, but I won't go into that now....  
	If you can, get your hands on a sketch of Kranz's anatomy to
better understand what I'm talking about.

Sorry this is so long!!  Hope it helps!

                               ------- * -------
	      "The roaring of lions, the howling of wolves, the 
	       raging of the stormy sea, and the destructive sword 
               are portions of eternity too great for the eye of man"
                                ~William Blake
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