C 3 plant

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Calvin cycle
D -3-phosphoglyceric acid the first stable CO 2 fixation product in C 3 plants. The eponymous chain of three carbon atoms is marked in blue .

C 3 plants (also Calvin plants ) work with the basic type of photosynthesis , the so-called C 3 photosynthesis. Since the stomata in hot and dry weather close to prevent too high evaporation of water, which in comparison to C 4 - or CAM plants under these conditions a reduced photosynthesis. However, they are more efficient in moderate temperature and light conditions.

Most of the plants in the middle and high latitudes belong to the C 3 plants. Examples of C 3 useful plants are wheat , rye , barley , oats , potatoes , soybeans , hemp or rice and all tree species worldwide, for C 4 plants maize , sugar cane or millet .

The fixation of carbon dioxide takes place in the Calvin cycle with the RuBisCO reaction on ribulose-1,5-bisphosphate ( RubP 2 for short ). The resulting intermediate stage is extremely unstable and spontaneously breaks down into two molecules of D -3-phosphoglycerate ( 3-PGA or G3P for short ), the first stable intermediate product in the C 3 plants. Since 3-PGA is made up of three carbon atoms , the name of this type of plant is derived from it.

In the history of the earth, the C 3 plants emerged first . Its key enzyme , ribulose-1,5-bisphosphate carboxylase / oxygenase ( RuBisCO ), appeared at a time when the atmosphere was rich in carbon dioxide (CO 2 ) and poor in oxygen (O 2 ). Assimilation was not a problem in this environment , as there were no losses due to photorespiration  - fixation of O 2 instead of CO 2  .

The maximum efficiency of C 3 photosynthesis is only achieved at over 1000 ppm CO 2 , below 150 ppm it comes to a complete standstill and the plant dies. Due to the increase in the CO 2 concentration since the industrial revolution, the photosynthesis performance of the C 3 plants has increased by approx. 40%. At the same time, the plants became more resistant to heat and drought, as they had to open their stomata less often.

Individual evidence

  1. http://www.spektrum.de/lexikon/biologie/c3- Pflanzen/ 15607 C3 plants

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