<P> The naming Hatch - Slack pathway is in honor of Marshall Davidson Hatch and C.R. Slack, who elucidated it in Australia in 1966 . </P> <P> The first experiments indicating that some plants do not use C carbon fixation but instead produce malate and aspartate in the first step of carbon fixation were done in the 1950s and early 1960s by Hugo P. Kortschak and Yuri Karpilov . The C pathway was elucidated by Marshall Davidson Hatch and C.R. Slack, in Australia, in 1966; it is sometimes called the Hatch - Slack pathway . </P> <P> In C plants, the first step in the light - independent reactions of photosynthesis involves the fixation of CO by the enzyme RuBisCO into 3 - phosphoglycerate . However, due to the dual carboxylase and oxygenase activity of RuBisCo, some part of the substrate is oxidized rather than carboxylated, resulting in loss of substrate and consumption of energy, in what is known as photorespiration . In order to bypass the photorespiration pathway, C plants have developed a mechanism to efficiently deliver CO to the RuBisCO enzyme . They utilize their specific leaf anatomy where chloroplasts exist not only in the mesophyll cells in the outer part of their leaves but in the bundle sheath cells as well . Instead of direct fixation to RuBisCO in the Calvin cycle, CO is incorporated into a 4 - carbon organic acid, which has the ability to regenerate CO in the chloroplasts of the bundle sheath cells . Bundle sheath cells can then utilize this CO to generate carbohydrates by the conventional C pathway . </P> <P> The first step in the pathway is the conversion of pyruvate to phosphoenolpyruvate (PEP), by the enzyme pyruvate orthophosphate dikinase . This reaction requires inorganic phosphate and ATP plus pyruvate, producing phosphoenolpyruvate, AMP, and inorganic pyrophosphate (PPi). The next step is the fixation of CO into oxaloacetate by the enzyme PEP carboxylase . Both of these steps occur in the mesophyll cells: </P>

What is the significance of the c4 pathway
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