CO . . Hatch & Slack Pathway or C4 Cycle or Dicarboxylic Acid Pathway or Dicarboxylation Pathway Till , Calvin cycle is the only pathway for CO fixation. But in , Kortschak , Hart and Burr made observations in sugarcane and found C or dicarboxylic acid pathway.
Malate and aspartate are the major labelled Figure . : C Cycle ADP ATP CO The C pathway Mesophyll cell PEP carboxylase Oxaloacetate (4c) PEP (3c) Malate (4c) Pyruvate (3c) CO calvin cycle Sugar Vascular tissue Bundle sheath cell C leaf anatomy stoma vein (vascular tissue) Mesophyll cell Bundle- sheath cell Photosynthetic cells of C plant leaf . . Significance of C cycle .
Plants having C cycle are mainly of tropical and sub-tropical regions and are able to survive in environment with low CO concentration. . C plants are partially adapted to drought conditions. .
Oxygen has no inhibitory effect on C cycle since PEP carboxylase is insensitive to O . . Due to absence of photorespiration, CO Compensation Point for C is lower than that of C plants. Differences between C Plants (C Cycle) and C Plants (C Cycle) are given in table .
. . . Stage: I Mesophyll Cells Phosphoenol Pyruvate CO (PEP) (3C) Oxaloacetic acid (OAA) (4C) PEP carboxylase Oxaloacetic acid (OAA) is converted into malic acid or aspartic acid and is transported to the bundle sheath cells through plasmodesmata.
. . Stage: II Bundle Sheath Cells Malic acid undergoes decarboxylation and produces a carbon compound Pyruvic acid and CO . The released CO combines with RUBP and follows the calvin cycle and finally sugar is released to the phloem.
Pyruvic acid is transported to the mesophyll cells. Rubisco RUBP CO PGA (5C) (3C) Activity • Collect the leaves of Paddy (C ) and Sugar cane (C ). • Take the cross section. • Observe the sections under the microscope.
• See the difference in their