![Until now scientists have had a poor handle on why some plant species evolved a much more efficient method of photosynthesis. A mathematical model has […]](/wp-content/uploads/2013/02/NEWSICON2-620x300.png "The maths of efficient photosynthesis")
Until now scientists have had a poor handle on why some plant species evolved a much more efficient method of photosynthesis. A mathematical model has now suggested that this characteristic evolved in several independent ways, increasing the possibility that these traits can be bred into important agricultural crops.
Around 90% of flowering plant species photosynthesise using the C3 photosynthetic pathway. However, 3% of plants (including species of maize, sugar cane and millet) have the ability to carry out an alternative type of photosynthesis, C4 photosynthesis. This type, evolving more recently, facilitated a 50% increase in efficiency in the conversion of carbon dioxide into organic compounds of use in the plant. C4 plants use 33% less water, grow more quickly, and take in thirteen times more carbon dioxide.
C4 photosynthesis allows photosynthesis to carry on when there is low carbon dioxide concentration in the leaf. Under conditions of increased temperatures, plants close the pores in their leaves to stop water leaving that has the unfortunate side effect of preventing carbon dioxide from entering. C4 plants have overcome this lack of carbon dioxide with a complicated molecular pathway that allows photosynthesis to carry on as normal under these conditions.
Researchers, led by the mathematician Dr Iain Johnston from Imperial College London and plant biologist Dr Ben Williams from the University of Cambridge, carried out a mathematical analysis of 73 species of C3 and C4 plants, looking at the 16 traits common in C4 plants. Their model showed that C4 photosynthesis evolved in multiple, independent ways and was the result of several small physiological changes. Interestingly, the structure of the leaf appears to have changed before any of the integral enzymes involved in photosynthesis changed. This study demonstrates how small changes could help breed C3 crops to make them more efficient and better able to cope with climate change.
