pathway named after the discoverers as Calvin-Benson Cycle. Dark reaction is temperature dependent and so it is also called thermo-chemical reaction. Dark reaction consists of three phases: (Figure . ).
. Carboxylation (fixation) . Reduction (Glycolytic Reversal) . Regeneration Phase - Carboxylation (Fixation) The acceptor molecule Ribulose , Bisphosphate (RUBP) a carbon compound Figure .
: Calvin cycle 4C ( ) -Phospho Glycerate Glyceraldehyde -Phosphate (G3P) pool Dihydroxy Acetone Phoshate (DHAP) DHAP DHAP Fructose , Bis Phosphate Fructose Phosphate Glucose Phosphate Glucose Phosphate Starch Erythrose Phosphate Sedoheptulose , Bis Phosphate Sedoheptulose Phosphate Ribose -Phosphate ( ) Ribulose -Phosphate ( ) Ribulose , -Bis Phosphate Xylulose Phosphate Xylulose Phosphate NADPH + NADP ATP ATP ADP+ P i ADP ( )CO Kinase Kinase Aldolase Aldolase Epimerase Isomerase Epimerase Phosphatase Phosphatase Dehydrogenase 3C 3C 3C 5C 5C 5C 5C 5C 6C 6C 7C 7C G3P G3P G3P G3P G3P G3P Export P i P i Stromal hexose phosphate pool RUBISCO Figure . : Phases of Calvin Cycle Check your grasp! What will be the quanta requirement for complete light reaction which releases oxygen molecules? Solution : Complete light reaction releases oxygen molecules.
If one molecule of oxygen evolution requires quanta means, for oxygen molecules × quanta of light required for complete light reaction. products. This observation was confirmed by Hatch & Slack in . This alternate pathway for the fixation of CO was found in several tropical and sub-tropical grasses and some dicots.
C cycle is discovered in more than species. Among them species belong to dicots and rest of them are monocots. C plants represent about % of Earth’s plant biomass and % of its known plant species. Despite this scarcity, they account for about % of terrestrial carbon fixation.
Increasing the proportion of C plants on earth could assist biosequestration of CO and represent an important climate change avoidance strategy. C pathway is completed in two phases, first phase takes