Chapter : 1. Nutrition
Dark Reaction
Dark Reaction : This reaction is not dependent on light. It is also known as calvin – Benson Cycle or C3 cycle as first stable product is phosphogliceric acid (PGA) a 3 carbon compound.
C4 Cycle or Hatch & Slakcycle :
4-C compound i.e. oxaloacetic acid (OAA).
This cycle is found in many other tropical & subtropical monocots eg : Maize, Sorghum , Wheat, Oat, Pearl, millet etc.
In dicots also many such plants are known eg : Amaranthus, Chenopodium, Atriplex, Euphorbia etc. In some families of dicots Compositae, Portulaceae, Nyctaginaceae.
Crassulacean Acid Metabolism (CAM) :
Certain plants, especially succulents which grow under extremely xeric (dry) condition, fix atmospheric CO2 in dark.
Since the process was first observed in the plants belonging to family crassulaceae (eg. Bryophyllum, kalanchoe etc.) It was termed crassulacean acid metabolism (CAM).
The most characteristic feature of these plants is that their stomata remain open at night (in dark) but closed during the day (in light).
Thus, CAM is a kind of adaptation in succulents to carry out photosynthesis without much loss of water.
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