Ehleringer, J. R., Monson, R. K. 1993.

Ehleringer, J. R., Monson, R. K. 1993. Evolutionary and ecological aspects of photosynthetic pathway variation. Annual review of ecology and systematics 24:411-439

Abstract

C4^[1] and ^[2] photosynthesis are evolutionarily derived from C3^[3] photosynthesis. The morphological and biochemical modifications necessary to achieve either C4 or CAM photosynthesis are thought to have independently arisen numerous times within different higher plant taxa. It is thought that C4 photosynthesis evolved in response to the low atmospheric CO₂ concentrations that arose sometime after the end of the Cretaceous. Low CO₂ concentrations result in significant increases in photorespiration of C3 plants, reducing productivity; both C3-C4 intermediate and C4 plants exhibit reduced photorespiration rates. In contrast, it may be argued that CAM arose either in response to selection of increased water-use efficiency or for increased carbon gain. Globally, all three pathways are widely distributed today, with a tendency toward ecological adaptation of C4 plants into warm, monsoonal climates and CAM plants into water-limited habitats. In an anthropogenically altered CO₂ environment, C4 plants may lose their competitive advantage over C3 plants.

Apostillas

1. ^ .
2. ^ . Crassulacean acid metabolism, also known as CAM photosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions. In a plant using full CAM, the stomata in the leaves remain shut during the day to reduce evapotranspiration, but open at night to collect carbon dioxide (CO₂). The CO₂ is stored as the four-carbon acid malate in vacuoles at night, and then in the daytime, the malate is transported to chloroplasts where it is converted back to CO₂, which is then used during photosynthesis. The pre-collected CO₂) is concentrated around the enzyme RuBisCO^[4] , increasing photosynthetic efficiency. This metabolism was first studied in plants of the Crassulaceae family. These mainly include succulents. The first time it was studied, Crassula was used as a model organism. CAM:wikipedia
3. ^ . C3 carbon fixation is one of three metabolic pathways for carbon fixation in photosynthesis, along with C4 and CAM. This process converts carbon dioxide and ribulose bisphosphate (RuBP, a 5-carbon sugar) into 3-phosphoglycerate through the following reaction:

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CO₂ + H₂O + RuBP → (2) 3-phosphoglycerate

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