Dark Reaction (Light Independent Reaction)

1.   Dark reaction (Calvin cycle):

Þ    2^nd 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.