The growth of crop plants is frequently restricted by how much nitrogen is present in the soil. The graph presents the findings of an investigation into the yield of a crop plant as the amount of nitrogen supplied is increased. Which of the following gives the best explanation for the form of this curve?
- Aprotein synthesis increases; DNA synthesis: no effect
- Bprotein synthesis: no effect; DNA synthesis: no effect
- Cprotein synthesis increases; DNA synthesis increases
- Dprotein synthesis: no effect; DNA synthesis increases