Difference between revisions of "C4 plant"

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C4 plant
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'''Definition'''
  
 
''noun''
 
''noun''
  
(Science: [[botany]]) a [[plant]] that utilizes the C4 pathway in which the CO<sub>2</sub> is first converted into a [[compound]] that has four [[carbon]] atoms (oxaloacetic acid)
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([[botany]])  
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(1) A [[plant]] that utilizes the C<sub>4</sub>  [[carbon fixation]] [[pathway]] in which the CO<sub>2</sub> is first bound to a [[phosphoenolpyruvate]] in [[mesophyll cell]] resulting in the formation of four-[[carbon]] [[compound]] ([[oxaloacetate]]) that is shuttled to the [[bundle sheath]] cell where it will be decarboxylated to liberate the CO<sub>2</sub> to be utilized in the C<sub>3</sub> pathway.
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(2) A plant in which the CO<sub>2</sub> is first fixed into a compound containing four [[carbon]] atoms before entering the [[Calvin cycle]] of [[photosynthesis]].
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'''Supplement'''
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A C<sub>4</sub> plant is better adapted than a C<sub>3</sub> plant in an [[environment]] with high daytime temperatures, intense sunlight, [[drought]], or [[nitrogen]] or CO<sub>2</sub> limitation. Most C<sub>4</sub> plants have a special [[leaf]] [[anatomy]] (called [[Kranz anatomy]]) in which the [[vascular bundle]]s are surrounded by [[bundle sheath]] [[cell]]s. Upon fixation of CO<sub>2</sub>into a 4-carbon [[compound]] in the [[mesophyll]] [[cells]], this [[compound]] is transported to the [[bundle sheath]] [[cells]] in which it is decarboxylated and the CO<sub>2</sub>is re-fixed via the C<sub>3</sub> pathway. The [[enzyme]] involved in this process is [[PEP carboxylase]]. In this mechanism, the tendency of rubisco (the first [[enzyme]] in the [[Calvin cycle]]) to photorespire, or waste energy by using [[oxygen]] to break down carbon [[compounds]] to CO<sub>2</sub>, is minimized.
  
A C4 plant is better adapted than a [[C3 plant]] in an [[environment]] with high daytime temperatures, intense sunlight, [[drought]], or [[nitrogen]] or CO<sub>2</sub> limitation. Most C4 plants have a special [[leaf]] [[anatomy]] (called [[Kranz anatomy]]) in which the [[vascular bundle]]s are surrounded by [[bundle sheath]] [[cell]]s. Upon fixation of CO<sub>2</sub>into a 4-carbon [[compound]] in the [[mesophyll]] [[cells]], this [[compound]] is transported to the [[bundle sheath]] [[cells]] in which it is decarboxylated and the CO<sub>2</sub>is re-fixed via the C3 pathway. The [[enzyme]] involved in this process is [[PEP carboxylase]]. In this mechanism, the tendency of RuBisCO (the first [[enzyme]] in the [[Calvin cycle]]) to photorespire, or waste energy by using [[oxygen]] to break down carbon [[compounds]] to CO<sub>2</sub>, is minimized.  
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Examples of C<sub>4</sub> plants include sugarcane, [[maize]], [[sorghum]], [[amaranth]], ''etc.''
  
Examples of C4 plants include sugarcane, [[maize]], [[sorghum]], [[amaranth]], ''etc.''
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''Compare:'' [[C3 plant]], [[CAM plant]].
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<br>''See also:'' [[C4 carbon fixation pathway]], [[Calvin cycle]].

Latest revision as of 10:10, 29 August 2008

Definition

noun

(botany)

(1) A plant that utilizes the C4 carbon fixation pathway in which the CO2 is first bound to a phosphoenolpyruvate in mesophyll cell resulting in the formation of four-carbon compound (oxaloacetate) that is shuttled to the bundle sheath cell where it will be decarboxylated to liberate the CO2 to be utilized in the C3 pathway.

(2) A plant in which the CO2 is first fixed into a compound containing four carbon atoms before entering the Calvin cycle of photosynthesis.


Supplement

A C4 plant is better adapted than a C3 plant in an environment with high daytime temperatures, intense sunlight, drought, or nitrogen or CO2 limitation. Most C4 plants have a special leaf anatomy (called Kranz anatomy) in which the vascular bundles are surrounded by bundle sheath cells. Upon fixation of CO2into a 4-carbon compound in the mesophyll cells, this compound is transported to the bundle sheath cells in which it is decarboxylated and the CO2is re-fixed via the C3 pathway. The enzyme involved in this process is PEP carboxylase. In this mechanism, the tendency of rubisco (the first enzyme in the Calvin cycle) to photorespire, or waste energy by using oxygen to break down carbon compounds to CO2, is minimized.

Examples of C4 plants include sugarcane, maize, sorghum, amaranth, etc.

Compare: C3 plant, CAM plant.
See also: C4 carbon fixation pathway, Calvin cycle.

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