ABSTRACT
Background Many of the most productive crops in agriculture use the C4 photosynthetic pathway. Despite their multiple origins, they are all characterized by high rates of photosynthesis and e cient use of water and nitrogen. As a morphological and biochemical innovation [1], the C4 photosynthetic pathway is proposed to have been an adaptation to hot, dry environments or CO2 deciency [2-5]. e C4 pathway independently appeared at least 50 times during angiosperm evolution [6,7]. Multiple origins of the C4 pathway within some angiosperm families [8,9] imply that its evolution may not be complex, perhaps suggesting that there may have been genetic pre-deposition in some C3 plants to C4 evolution [6].
