The C₄-plants are different from the C₃-plants with reference to the

The C₄ plants are different from the C₃ plants with reference to the substance that accepts CO₂ in carbon assimilation.
In C₄ plants, CO₂ is assimilated by condensing with PEP, with the help of the PEPCase enzyme to yield the first stable product, four carbon compound OAA.
Whereas In the C₃ plants, CO₂ is assimilated by condensing with RuBP with the help of RuBisCO enzyme to yield the first stable product, the three-carbon compound PGA.