Hatch and Slack path way:
Two Australian botanists Hatch and Slack (1966) discovered that there are two types of chloroplasts in sugarcane. One type restricted to bundle sheath cells has the usual grana. These chloroplasts carry on Hatch-Slack or C4 cycle.
The invention of C4 cycle in monocots such as sugarcane, maize and sorghum has indicated that these plants have solved the difficulty of photorespiration. The carbon dioxide is fixed in the mesophyll cells.
- Atmospheric CO2 enters the mesophyll tissue where it forms oxalic acetic acid by uniting with phosphoenol pyruvic acid.
- Oxalic acetic acid is turned into malic acid by receiving 2H+ from NADH + H+.
- Malic acid transforms into pyruvic acid in presence of NADP and malic acid dehydrogenises.
- Again, pyruvic acid is turned into phosphoenol pyruvic acid.
- A carbon oxalo acetic acid is the first stable compound in this cycle.