The usage of this pathway is indicated by a higher tissue ratio of carbon-13 to carbon-12. The rapid spread of this pathway in the late Miocene is hypothesized as due to increased disturbances by fire. This pathway was discovered in pulse-chase experiments performed by Marshall Hatch and Roger Slack. This pathway's name comes from the formula of (-5[1])oxaloacetate (ock-suh-loh-ASS-uh-tate), which (10[1])during this pathway is (-5[1])converted into (-5[1])aspartate or malate, then (10[1])transported out of (-5[1])the mesophyll (10[1])(MEH-suh-fil) cell. An international (-5[1])research project founded in 2008 seeks to introduce genes for this pathway into rice crops. In this pathway characterized by kranz (krants) anatomy, the Calvin cycle is performed (-5[1])separately in bundle sheath cells in the absence of oxygen, lowering the rate of photorespiration. For 10 points, name this type of photosynthesis that's sometimes more efficient (10[4]0[2])than C3. ■END■