A type of organization of the photosynthetic tissues found in the leaves of *C4 plants
. In such plants the cells of the bundle sheath are large and contain specialized elongated chloroplasts with no grana but capable of forming starch grains. The mesophyll chloroplasts are similar in structure to those of C3 plants but do not form starch grains. It is within the mesophyll chloroplasts that oxaloacetic acid is formed through the combination of carbon dioxide and phosphoenolpyruvate. This is then transported to the bundle sheath chloroplasts where the carbon dioxide is released and refixed by ribulose bisphosphate carboxylase.