Thursday, January 13, 2011

Dark Reaction (Light Independent Reaction)

1.   Dark reaction (Calvin cycle):
Þ    2nd stage of photosynthesis
Þ    CO2 - converted into sugar.
Þ    takes place in the stroma (of chloroplast + bundle sheath cells).
Þ    not dependent on light.
Þ    cyclic process of enzyme catalyzed reactions. 
2.   It involves three steps:
Þ    CO2 fixation
Þ    reduction
Þ    regeneration.
3.   During CO2 fixation:
Þ CO2 combines with RuBP(5C) to form G3P (catalysed by Rubisco - also involved in the photorespiration process).
Þ  first product = glyceraldehyde 3 phosphate (G3P)
4.  ATP and NADPH are utilised (from light reaction).
5.  5 molecules of G3P are utilised for regeneration of RuBP.
4.  C3, C4 and CAM plants (have different anatomy + physiology)
5.  C3 plants:
Þ    mesophyll cells have chlorophyll.
Þ    open their stomata during the night.
Þ    live in moderate climate.
6.  C4 plants:
Þ    have mesophyll cells + bundle sheath cells.
Þ    have Krantz anatomy.
Þ    live in dry climatic conditions.
Þ    adapt themselves to prevent water loss by closing stomata during day time.

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