Suppose atmospheric carbon dioxide levels rise dramatically in the future.How do you predict this will affect competition between C₃ and C₄ plants? A) C₃ and C₄ plants will compete equally, since both use the same stoichiometry of carbon dioxide to water in the overall photosynthetic reaction. B) C₃ plants will outcompete C₄ plants, since C₄ plants must use more energy in the carbon fixation phase of photosynthesis than C₃ plants. C) C₃ plants will outcompete C₄ plants, since there are many more species of C₃ plants than C₄ species. D) C₄ plants will outcompete C₃ plants, since C₃ plants are not hampered by photorespiration and C₄ plants are hampered by this rubisco activity. E) C₃ plants will outcompete C₄ plants, since C₃ plants can store fixed carbon in four-carbon organic molecules in mesophyll cells until needed for Calvin cycle reactions.

Question

Quizplus · Accepted Answer

C3 plants (C₃) will outcompete C4 plants (C₄) under high CO2 conditions because C4 plants have a mechanism to efficiently fix carbon at lower CO2 concentrations, which becomes less advantageous as CO2 levels rise. C3 plants, on the other hand, directly benefit from increased CO2 without the need for the additional energy expenditure required for the C4 pathway.

Suppose Atmospheric Carbon Dioxide Levels Rise Dramatically in the Future