Final answer:
True, C4 and CAM plants use PEP carboxylase to capture CO2. CAM plants are more water efficient than C4 plants, not due to the enzyme efficiency but because they open their stomata at night. However, C4 photosynthesis is more energy-intensive than C3 photosynthesis. Both C4 and CAM photosynthesis are favored by warm temperatures.
Step-by-step explanation:
The statement A) C4 and CAM plants use PEP carboxylase to capture CO2 is true. Both C4 and CAM plants use the enzyme PEP carboxylase for the initial fixation of CO2 to form a four-carbon compound, which is then transported and processed differently in each plant type.
B) CAM plants are more water efficient than C4 plants is partly true. While CAM plants are indeed more water efficient because they open their stomata at night to reduce water loss, it is not because CAM plants have a more efficient form of PEP carboxylase. Both C4 and CAM plants use the same enzyme, but their water-use efficiency is due to the timing of stomatal opening, not the efficiency of the enzyme.
C) Both CAM and C4 plants require less energy than C3 plants is not true. C4 photosynthesis requires more energy (ATP) than C3 because of an additional set of steps prior to the C3 cycle. However, the energy cost is offset by enhanced water efficiency and carbon fixation efficiency under high-temperature conditions.
Finally, D) Warm temperatures favor CAM metabolism, but not really C4 is not true. Warm temperatures also favor C4 metabolism, as these conditions make C4 photosynthesis more efficient relative to C3 photosynthesis, allowing for more effective carbon fixation and water use under such conditions.